THE SECRET AGENT ON FLIGHT 101

Rarely do magicians reveal their professional secrets. Consequently Frank and Joe Hardy are amazed when a well-known magician, the Incredible Hexton, offers to reveal the secret of his âVanishing Man Actâ and invites Mr. Hardy to be the subject. When their detective father fails to reappear, his sons are convinced that something sinister is afoot, despite Hextonâs insistence that Mr. Hardy is playing a joke on them.

While desperately searching for their father, Frank and Joe find themselves working with SKOOL, a U.S. organization of crack secret agents pitted against UGLI, an international ring of spies stealing government secrets from the U.S. and other democratic countries.

In a lighthouse off the coast of New England and in Scotland, Frank and Joe and their pal Chet Morton grimly match wits with UGLIâs evil agents. With cool daring the three boys invade the magicianâs Scottish castle, where an astounding surprise awaits them.

The young detectivesâ gripping adventures culminate in a dramatic climax when they unmask the secret agent on Flight 101.

âGood luck, lad!â the pilot called

Copyright Â© 1995, 1967 by Simon & Schuster, Inc. All rights reserved.

Published by Grosset & Dunlap, Inc., a member of The Putnam & Grosset group, New York. Published simultaneously in Canada. S.A.

THE HARDY BOYSÂ® is a registered trademark of Simon & Schuster, Inc. GROSSET & DUNLAP is a trademark of Grosset & Dunlap, Inc.

library of Congress Catalog Card Number: AC67-10521

eISBN : 978-1-101-07659-0

http://us.penguingroup.com

CHAPTER I

A Vanishing Act

âHow can the hand be quicker than the eye?â asked Chet Morton. âThatâs hard to believe!â He climbed into the back seat of the Hardy boysâ convertible next to Joe.

âPerhaps the Incredible Hexton will convince you,â remarked Frank, who was at the wheel. âAll set, Dad?â he asked the handsome man beside him.

âTake off!â Mr. Hardy said, smiling.

It was Friday evening. Bayport High had closed for summer vacation the day before. To celebrate, the Hardy boys and their stout friend Chet were being treated to a magicianâs show in the nearby city of Claymore.

âI read in a newspaper,â Chet went on, âhow pickpockets use sleight-of-hand methods. In fact, I have the clipping here in myââ Suddenly he sat bolt upright. âMy wallet!â he cried. âItâs gone!â Frank brought the car to a stop. âAre you sure?â he asked.

Chet searched his pockets frantically. âItâs gone all right!â

âProbably dropped out when you got into the car,â Frank suggested.

âThen weâd better go back,â Mr. Hardy said.

Joe tried to hide a grin. But Chet noticed it. âWait a minute!â He eyed Joe suspiciously. âOkay, mastermind. Hand it over!â

Joe burst out laughing and gave his chum a brown leather wallet. âJust wanted to prove to you the hand really is quicker than the eye.â

âYou caught me off guard,â Chet replied goodnaturedly.

Joe Hardy, blond and seventeen, enjoyed joking and was more impulsive than his dark-haired, eighteen-year-old brother. Both boys were trim all-around athletes. Chet, their schoolmate, had a chunky build and played on the Bayport High football team.

âLetâs go, boys!â said Fenton Hardy, grinning. âAny more pocket-picking and Iâll pull you in!â

Frank and Joeâs father was a nationally known detective who had earned his fame as a member of the New York City Police Department. After his retirement from the force, he had set up his own sleuthing organization. Both sons were following in his footsteps and already had solved many challenging mysteries on their own. Chet often joined in their adventures. Although the stout boy preferred safer pursuits, no danger could make him desert his friends.

âWhat do you know about Hexton the magician?â Frank asked his father.

Mr. Hardy said the man was a performer of some renown throughout the world, and was much acclaimed for his demonstrations of sleight of hand.

Joe asked, âDad, do you by any chance have a professional interest in him?â

The detective laughed but did not reply and Joe decided not to press his query further. But he sensed that he had hit upon the truth.

They drove into Claymore, parked in the lot behind the theater, and took their seats just as the houselights dimmed. A tall, dark figure slipped through the curtains and the spotlight blazed upon the Incredible Hexton.

The gaunt magician wore a top hat, flowing black cape, and carried a silver-handled cane. His face sent a chill through Chet.

Hexton had heavy brows, a sharply pointed chin, and the piercing eyes of a medieval sorcerer. He moved into his performance with a cat-like grace which indicated a disciplined and powerful body.

The boys watched eagerly as the magician caused coins, cards, and other small objects to disappear, then reappear at his fingertips.

The finale of the show was billed as the âVanishing Man Act.â Hexton led a short, muscular aide to a boxlike compartment, walled in on three sides by curtains and on the front by draperies. He opened and closed these a couple of times. Inside the curtained area was what looked like an oversized picture frame, supported at each end by posts.

Hextonâs aide was strapped to a plank, which the magician and a tall, thin assistant set horizontally into the frame. This was tilted toward the audience at a forty-five-degree angle.

Hexton closed the small curtain and gestured with his cane. In seconds the curtain was reopened. The audience gasped in amazement! The magicianâs aide, and the plank to which he had been strapped, had vanished!

Hexton bowed low, and his aide strolled onto the stage from the wings, to thunderous applause from the audience. Hexton bowed several times more, and stepped behind the curtain.

âGreat performance!â Frank said as he rose from his seat and stretched.

âDo you know how he did it, Dad?â Joe asked.

âI have an idea. Letâs go backstage. I think it would be interesting to talk to Hexton.â

The detective and his three companions made their way to a door at the side of the stage. They went through it and up a short flight of steps to the wing, where they found Hexton.

Mr. Hardy introduced himself and his party. âYou had us baffled,â he said. âGood show!â

âEspecially the last trick,â said Joe. âThat was great!â

The performer smiled cordially. âPerhaps you would like to see how it is done.â

Frank looked surprised. âI thought magicians never gave away their secrets.â

âCustomarily they donât,â Hexton replied smoothly, âbut, you see, I have recognized your name. I know Fenton Hardy is a star performer in his own field. We both deal in secrets. Mr. Hardy, my job is to mystify, yours just the opposite. I will show you the trick as a professional courtesy.â

âThatâs very gracious of you,â the detective replied.

âNot at all,â Hexton said quickly. âI have a feeling we ought to become better acquainted.â

Mr. Hardy smiled. âAn excellent idea.â

âOne moment,â said Hexton. âI must alert my assistant. In the meantime, will you boys please take seats down in the auditorium.â Hexton strode off but returned in a couple of minutes. âFollow me, Mr. Hardy.â

He led the detective onstage in the now-empty theater. âWould you do me the honor of being my subject?â he asked with a sweeping bow.

The short assistant strapped Fenton Hardy to the plank. With the three boys watching intently, the magician closed the curtain and waved his cane. When he opened the compartment, the subject had vanished.

âThatâs neat!â Chet said.

The boys watched for Mr. Hardy to reappear. When some time went by and he did not come out of the wings, Frank and Joe became worried.

âWhatâs happened?â Frank asked anxiously. He and Joe ran onto the stage to examine the compartment, but Hexton blocked them.

âI canât permit you to inspect my device,â he said, dropping his pleasant manner.

âThen tell us where our father is!â Joe demanded.

âI donât know,â Hexton said slyly. âHe must be playing some kind of joke on you.â

Joe moved toward the magician. âStep aside. Weâre going to take a look at that gadget of yours.â

Hexton called quickly, âVordo! Stony!â

Two men emerged from the wings. The first one appeared to be nearly seven feet tall. His massive shoulders, muscular arms, and hard features made him a formidable sight. The other was the thin fellow who had helped with the vanishing act.

âSee to it that these boys leave immediately,â the magician ordered.

Joe was ready to fight, but Frank caught his brotherâs upraised arm. Perhaps Hexton was telling the truth.

The assistant strapped Mr. Hardy to the plank

Joe acceded. âAll right, have it your way!â he said. âBut weâll be back!â

The trio hurried out of the theater. Joe insisted upon going to nearby Claymore Police Headquarters to request that a couple of officers go back to investigate.

âAll right,â said Frank.

When the group returned to the theater, Hexton became enraged. âIf you try to look at my equipment without a warrant, Iâll sue you!â he stormed.

The officer told the boys that since there was no evidence of a crime, the only thing they could do was to file a missing-persons report.

âBut we canât just sit around and wait!â Joe declared hotly.

âOn the other hand, itâs possible Dad is staying away on purpose,â Frank reasoned in a low tone. âLetâs wait a while before we report him missing.â

Joe was not satisfied. âAt least letâs search the theater.â

The police agreed to this and the manager was summoned. He gave permission, but stressed the point that he had no jurisdiction over Hextonâs equipment.

The magician and his assistants glared at the Hardys and Chet as they inspected the stage thoroughly. Then they searched other sections of the theater. There was no sign of Fenton Hardy. Frank suggested that they return home, in the hope that his father would try to reach them there.

Deeply worried, the three boys hurried across the dark parking lot and got into the Hardy car. As they sped along a straight stretch of road leading from the city, Chet looked out the rear window. He noticed the headlights of a pickup truck drawing swiftly closer.

âSome character is tailgating us,â Chet said. âDoesnât he know thatâs dangerous?â

âBest thing is to let him go by,â Frank replied, and pulled closer to the shoulder of the road.

The small truck roared past the Hardysâ car.

âA speed demon!â Joe said sarcastically as the truck disappeared from sight.

The route Frank had chosen led them along a narrow, winding mountain road, bordered on one side by a guard rail. Below it was a sheer drop of several hundred feet.

As the car rounded a sharp curve, the boys were horror-stricken to see the headlights of a car directly in front of them. They had only the fraction of a second to brace themselves for a collision!

CHAPTER II

The Hexton File

CRASH! There was a loud, piercing sound of shattering glass as the oncoming headlights made contact. Yet there was no collision! Like an apparition, the other vehicle had vanished completely.

Frank struggled to maneuver the car away from the guard rail. He jammed on the brakes and skidded to a stop. They all looked startled.

âWh-what happened?â Chet asked.

âI donât know,â Frank said. âThis is weirdââ

Joe pulled out a flashlight. âLetâs go back up the road and investigate!â

The boys walked to where they had encountered the headlights. As Joe played the beam along the road, they noticed broken glass scattered about. Frank picked up a fragment.

âLook at this!â he said.

âItâs a piece of mirror!â exclaimed Chet.

âSo thatâs it!â Frank exploded. âSomeone set a mirror on the road. What we saw was the reflection of our own headlights!â

Joeâs eyes widened in anger. âWe might have swerved over the embankment!â

âExactly!â Frank answered. âWhoever planted the glass put it too close to the bend in the road. We came upon it so quickly I didnât have time to swerve!â

The young sleuths wondered if Hexton or his assistants had set the trap for them. Or had it been intended for another unsuspecting victim?

âThis mystery is getting too dangerous,â Chet said gravely. âA guy could get hurt.â

âDonât worry. Weâll get to the bottom of it,â Frank vowed.

The Hardys searched the area more closely. Joe picked up a sliver of wood. He noticed several similar pieces scattered along the road.

âWhat do you make of this?â he asked.

Frank examined it. âUndoubtedly this is part of a wooden easel that was used to support the mirror.â

âMagicians often use them in their acts,â remarked Joe. âHexton could have had a big mirror brought here in a pickup truck.â

Frank agreed. âThe one that passed us was certainly traveling fast enough to reach this spot well ahead of us.â

âIf Hexton did plant the mirror, how could he know weâd take this road?â Chet inquired.

âItâs the fastest way back to Bayport,â Frank replied. âHe may have had us followed.â

After scuffing the glass and wood off the road, the boys drove on. At the Morton farm on the outskirts of Bayport, Chet got out.

âSâlong, fellows,â he said. âKeep me posted about your dad.â

Frank and Joe drove home in silence. Their mother and Aunt Gertrude were waiting for them in the living room. Reluctantly the boys told what had happened.

âOh dear!â their aunt shrilled. âQuick! Call the police. Fentonâs been kidnapped!â

Gertrude Hardy, tall and angular, was the sister of Fenton Hardy. Although she admired the sleuthing abilities of her brother and nephews, she constantly worried about the dangers involved.

Mrs. Hardy, an attractive and gracious woman, was too stunned by the shock of her husbandâs disappearance to talk. Frank put a comforting arm about her.

âIn case Dad disappeared on purpose, letâs not notify the police. Joe and I will find him. He may not be far away.â

The boys excused themselves, then went to their fatherâs study.

âI think Auntyâs right about the kidnapping,â said Joe. âDad must have had something pretty big on Hexton.â

âIn that case,â Frank said, âwe ought to find it in his files.â

But there was no record of Hexton under the letter H.

âTry M for magician,â Joe suggested.

Frank looked. âNot there.â

They checked several other headings, but did not find any mention of the man. Then Joe noticed a folder marked âSchool.â

âThatâs funny,â he said. âI donât remember Dad having a case to do with a school.â

He took out the file and opened it. âFrank! Look here! This is it!â

Fascinated, the boys read the notes. Mr. Hardy described the magician as a diabolical man who for years had headed a gang of thieves. Working as the crew for his show, they moved about the country with him, pulling the robberies he planned. The detective had discovered the setup recently. âSo far no real evidence,â he had noted. Written at the bottom of the page was: âLast two years agent UGLI.â

âUGLI!â Joe exclaimed. âUndercover Global League of Informants!â

Frank gave a low whistle. âThis is really big! UGLI is the most powerful espionage ring in the world.â

âAnd hostile to democratic countries,â added Joe.

The boys exchanged grim looks. If their father had been kidnapped, he was in ruthless hands!

âI think I know now why this is filed under school,â said Frank.

Joe nodded. âThatâs probably a camouflage word for SKOOL. Dad must be working for them.â

Both boys had heard of the famous supranational counterespionage ring which worked on behalf of democratic powers. The letters stood for Secret Knowledge Of Organized Lawbreakers.

âIf only we could contact them,â said Frank, âthey might be able to give us a lead. But the organization is so secret, thereâs no way to reach them.â

âUnless theyâve called you first,â said Joe. âMaybe Dad left a note on how to get in touch.â

But a thorough search turned up no information. The boys perused the report again and learned that for the past two years State Department secrets had been leaking out of Washington to enemy countries at an increasing rate. The detective had written, âOffices, cars, and homes of diplomatic corps must be very cleverly bugged. Agents probably transmit microtape to couriers who take it abroad.â

On the margin at the left were the words, âSee Dell.â

Frank and Joe searched the file and all the other drawers in the room, but could find no further reference to Dell. Who was he?

Before they put the Hexton report away, Frank read aloud the note at the end of it: â âDo not think Hexton is aware of investigation. Perhaps should discuss with Frank and Joe when more substantial evidence is found.â â

âItâs dated yesterday!â Joe exclaimed.

âSomehow Hexton must have learned that Dad was onto his game,â Frank observed.

âAnd our showing up at the theater,â Joe said, âprobably made him nervous. So he pulled a kidnapping.â

Frank reminded Joe of the magicianâs suggestion that the two men get better acquainted. âIâll bet Dad thought if he went along with the idea he might be able to get the goods on Hexton. The first step was taking part in the trick.â

âBut what a risk!â said Joe.

âYou know Dad,â Frank said quietly. âIf he figured it was worth while, heâd take it.â

The night wore on with no word. Finally Aunt Gertrude insisted upon phoning a missing-persons report to the Bayport police. The next morning there was still no word from the detective, and the police had found nothing.

Frank and Joe decided to drive back to Claymore. They arrived at the theater to find the front door locked. Walking around to the back, they were confronted by a guard. He told them that Hexton had given his last performance the night before and had already departed. The magician had left two of his assistants behind to supervise the packing of the showâs equipment.

âOur father disappeared here last evening,â Frank said. âWeâd like to have a look inside.â

âSorry,â the guard answered, âI canât permit anyone in the theater. Managerâs orders.â

âThen weâd like to see him,â Joe said.

âHeâs not here. Iâd advise you to go.â

âOkay,â Frank signaled Joe with his eyes and the two walked off briskly around the side of the building. There they stopped abruptly and Frank peered back.

After a few minutes the guard left his post and disappeared around the far corner.

âLetâs go!â Frank commanded.

Quietly the boys edged their way toward the stage door. They pulled it open and darted inside, stopping to let their eyes adjust to the dim light. Then, cautiously, they made their way to the stage. Nobody was around.

âWhere are Hextonâs men?â Joe whispered.

âOut for a coffee break,â Frank guessed.

The stage was cluttered with packing cases containing the magicianâs equipment. At the rear the boys spotted the vanishing-man device. It had already been partially dismantled.

âLook! The plankâs missing,â Joe said. âMaybe packed in one of these cases.â

Further examination of the device revealed that it had a false bottom, beneath which was a secret compartment.

A soft rustling noise had sounded overhead. âWhatâs that?â Frank said. He glanced up in time to see a ballast sandbag hurtling down toward them from the flies.

âLook out!â Frank shouted. He leaped aside, pulling Joe with him. The sandbag crashed to the stage and burst open. The boys looked up and saw a man running along a catwalk.

âAfter him!â Joe yelled.

âHold it!â commanded a harsh voice. âStay right where you are!â

CHAPTER III

The SKOOL Man

THE Hardys whirled to see the theater guard approaching. âSo itâs you two!â he shouted angrily. âDidnât I tell you to shove off?â

âYes, butââ Joe began.

âThat crashââ the guard cut in. âWhat happened?â He looked at the sand scattered about the stage.

âSomeone tried to drop a sandbag on us,â Frank explained.

âA likely story.â The guard eyed the boys suspiciously. âYouâre probably up to something. Iâm calling the police!â

Keeping an eye on the boys, the guard walked to a wall telephone and dialed. Within minutes an officer arrived.

âOh, the Hardy brothers,â he said, and turned to the guard. âI heard about these kids. Theyâre trying to find their father.â

âI thought that was a gag,â the man replied.

âNo. Itâs on the up and up.â

The guard apologized and helped the young sleuths examine the sandbag. They discovered that the ropes which held it had been cut.

At that moment the magicianâs thin assistant walked onstage. When the policeman questioned him, he gave his name as Stony Bleeker. The man said he had been out for a walk and insisted he had had nothing to do with dropping the sandbag.

âWhereâs the other man who was helping you pack?â Frank asked.

âHow should I know?â

âI suppose youâre going to tell us that you donât know what happened to our father, either!â Joe said.

âYouâre nuts!â Bleeker growled.

The Hardys climbed up to examine the flies, but there was no trace of their attacker. âHe must have sneaked down the ladder and out the side door while we were hassling with the guard,â said Joe.

Back on the stage, the boys found further questioning fruitless. The policeman said he would request that the detective squad investigate the matter.

Stony Bleeker quickly set about packing the rest of Hextonâs equipment, telling the policeman that a truck would call for it shortly.

âWell, thatâs that!â Frank said glumly. âCome on, Joe. Letâs go home.â

On the way back to Bayport, the boys decided to search their fatherâs study again.

âMaybe we can find out who or what Dell is,â Frank said. âThat might give us a lead.â

But their efforts were of no avail until Frank examined the books on his fatherâs desk. A torn envelope flap was sticking to the back cover of one. On it was the notation, âKenneth Dell, Great Circle Airways, Westboro, 789-1010.â

âYou found it!â Joe exclaimed.

The boys surmised that their father had put the book down on the gummed paper and failed to notice later that it had stuck to the cover.

Quickly Frank dialed the Westboro number. A man with a deep, commanding voice answered and identified himself as Kenneth Dell. Frank explained why he had called, and Dell revealed that he was chief of security for Great Circle Airways.

Amazed to hear about the disappearance of Mr. Hardy, Dell said it was imperative that he talk to the young detectives and he would fly to Bayport the following day.

âMeet me outside the airport restaurant at twelve-thirty,â Dell said. âI donât want to come to your home for fear weâre being watched by Hextonâs men. Iâll explain everything when I see you.â

After church the next day, Frank and Joe drove through the heavy Sunday traffic to the airport and anxiously awaited the security chiefâs arrival at the restaurant. Soon they were approached by a tall, stocky man, with distinguished features and slightly grizzled hair. Accompanying him was a thin, gray-haired man in a dark suit.

âYouâre the Hardy boys, I take it,â said the stocky one. âIâm Dell. This is Mr. Smith.â

Both men shook hands and Dell added, âYour father has told me a lot about you two. Heâs very proudâsays his sons are great detectives.â

The four entered the restaurant and seated themselves at a table by a front window. Mr. Smith kept looking down at his hands.

âWho is he?â Frank wondered.

Both boys noticed that Mr. Smith was twisting a crested gold ring on his finger.

âLooks like a school emblem,â Frank thought, then suddenly realized what the man was telling him. âHeâs from SKOOL!â

Joe got the message at the same time and threw a quick glance at his brother.

Dell smiled. âI felt sure you would understand. It is safer if some things are not said aloud. Mr. Smith and I work together.â So Dell was also a member of SKOOL, working under the guise of security officer for Great Circle Airways!

He went on to say that Mr. Hardy had come to him some weeks before and asked for dossiers on all employees and the passenger lists for the past two years. âI supplied the information.â

Dell was interrupted for a minute while a waitress took their orders. Smith gave none. Then the security chief leaned closer.

âYour father found out that Hexton owns a castle in the north of Scotland. Itâs a retreat, the magician claims, where he rests and devises new tricks for his show. He goes there several times a month on our planes.â

âSounds like a great setup for smuggling secrets out of this country,â Frank said softly.

âThatâs just what your father concluded,â Smith said. âBut he disappeared before he had a chance to give me a detailed report. So far nothing has been proved.â

In turn, Frank and Joe quickly told about the information they had gleaned from Mr. Hardyâs file on Hexton.

âWhere is Dadâ Frank asked urgently. âHave you any idea??â

âI had a reliable tip that Hexton has taken him to South Africa,â Smith replied. âMy organization will move in on the situation there.â He glanced at his watch and abruptly stood up. âIf you need me, contact Mr. Dell. Good luck.â He walked off quietly.

A few moments later the food came. As they were eating, Joe suddenly exclaimed, âLook!â He clutched his brotherâs arm and pointed toward the large front window of the restaurant.

âWhat is it?â

âA man just peered in here! Iâm sure heâs Stony Bleeker!â

The boys darted outside, followed by Dell. But Bleeker was not among the passers-by.

âMaybe he ran around back!â Joe suggested.

âQuick!â Frank ordered. âLetâs split up and check the building on all sides! Joe, you stay here in front! Mr. Dell, Iâll take the east side, if youâll take the west!â

âLetâs go!â the security chief agreed.

Frank raced along the east side of the building. Carefully he rounded the corner, but did not spot Bleeker. Just then he heard sounds of a scuffle coming from around the far side.

âUhff!â someone groaned.

Frank ran to the spot to find Dell lying on the ground. He bent over the prostrate man.

âAre you all right?â Frank asked worriedly. He helped the security chief to his feet.

âI almost had him,â Dell said, breathing heavily. âBut he got in a fast punch.â Dell pointed. âThere he goes now!â

Frank turned and saw Bleeker dashing into the airport parking lot. The boy bolted after him. The man had too big a lead, though. Before Frank could reach him, Bleeker scrambled into a car and sped away. Disappointed, Frank returned to the restaurant. Dell was already there.

âAny luck?â Joe asked his brother.

âNo. Didnât even get the license plate number.â

âBleekerâs thin,â Dell commented as he rubbed his chin, âbut he packs a lot of power.â

âWhatâll we do now?â Joe asked.

Frank thought for a moment. âWeâll check the list of cities scheduled on Hextonâs tour. If we can trail him without his knowing it, we might trap him into revealing where he took Dad.â

âI still have a copy of the playbill from his last show,â Joe recalled. âI believe his tour schedule is listed in it.â

âGood thinking,â Dell remarked. He instructed the boys to call him if they wanted help. Then he boarded a plane to return to the Great Circle Airways base at Westboro near New York City.

âLetâs go home and check that playbill right away,â Frank said.

âHexton knows that weâre on to him and his gang,â Joe remarked. âDo you think heâll continue with his tour?â

âProbably not,â Frank answered. âBut right now itâs our only chance to find him.â

When they returned to their car, the Hardys were surprised to see a pencil-printed note attached to the steering wheel. Frank removed it and read the contents aloud:

ââMind your own business! Or youâll never see your father again!â â

CHAPTER IV

Cryptic Message

âBLEEKER must have left the warning here!â Joe exclaimed.

âThatâs for sure,â Frank agreed. âAnd itâs no idle threat. Besides, I have a hunch Dad wasnât taken to South Africa. Otherwise, Hexton wouldnât be so determined to keep us off the trail.â

The Hardys were more eager than ever to get their investigation under way. Upon arriving home, they examined the playbill which listed the cities on the magicianâs tour.

âAccording to this list,â Frank observed, âHexton is scheduled to appear at the Tivoli Theater in Darville tomorrow.â

Joe paged through the atlas and pinpointed the location of the city. âHereâs Darville. Itâs about four hundred miles from here.â

The boys telephoned Jack Wayne, pilot of Mr. Hardyâs twin-engine plane, and arranged to fly to Darville the following day. Frank and Joe had private pilot licenses, but thought it wise to have Jack along. âHeâs a tough man in a fight,â Joe said.

When they invited Chet, he eagerly accepted. âIâll meet you at the field.â

The next morning Mrs. Hardy and Aunt Gertrude nervously prepared breakfast for the young detectives.

âNow donât do anything foolish,â their mother cautioned. âThis Hexton fellow sounds terribly dangerous to me.â

âI fear the worst!â Aunt Gertrude said, shaking her head. âDetective work involves taking too many chances. No good will come of this. I can feel it in my bones.â

âDonât worry about us,â Joe assured them. âHexton might be a clever magician, but we have a few tricks of our own.â

After receiving more admonitions at the doorway, the boys drove to the airport. Jack Wayne, the tanned, lean-faced pilot, was waiting for them at the plane. Chet came puffing up a few moments later. Soon they were airborne and streaking toward Darville. Two hours later they circled it and set down.

Frank rented a car and they drove directly to the theater where Hexton was scheduled to appear. As they approached the Tivoli, the boys were amazed to see a man standing on a tall ladder against the marquee, removing the big black letters which spelled out the magicianâs name.

Frank pulled up in front of the theater, and Joe called out, âWhatâs going on? Hextonâs first show is scheduled for tonight!â

The man on the ladder shrugged. âI only follow orders. Sorry.â

He pointed to the box-office window. A cancellation notice was spread across a large poster advertising the show.

âLetâs have a talk with the theater manager,â Frank suggested. He parked and they hastened to a door marked âManager L. Sardella.â Joe rapped loudly.

âCome in!â

When the four entered, a small, thin man with a waxed mustache removed his feet from a desk and glowered. âYes?â

âMr. Sardella, where is Hexton?â Joe asked tensely.

The man arose and eyed them sharply. âYou want refunds?â

âNo. Weâre private detectives,â Chet said importantly. âWhere is he?â

âHexton? Thatâs what Iâd like to know. The skunk! Iâll spend the rest of the day giving refunds on my advance ticket sale, and still have no show tonight.â

âWhy didnât he come?â Frank asked.

âSearch me. He phoned long-distance. Gave no reasons. Iâll sue him!â

Sardella said that the magician had mentioned he was canceling the remainder of his tour with the exception of one last performance.

âWhere?â Frank asked.

âSome little place called Granton. Donât ask me what state, because I donât know. Said they pushed up the date to tonight to accommodate him. Accommodationâbah!â

The Hardys and their friends thanked the manager and hurried back to the car. They returned to the airport and hastened to the operations room to consult a large aeronautical chart mounted on the wall.

âHereâs Granton,â the pilot said, pointing. He quickly plotted a course. âItâs a little bit more than a thousand miles from here.â

âGood grief!â Chet exclaimed. âWeâll never get there in time.â

Frank glanced at his watch. âWe ought to be able to make the trip in under seven hours, wouldnât you say, Jack?â

The pilot manipulated a small flight computer, which he had taken from a jacket pocket. âWith the present winds, Iâd say we could do it in seven hours easily.â

âIf we take off right now,â Frank said, âwe can be in Granton before Hextonâs show ends.â

âIâm game, fellows,â Chet piped up, âif youâll let me get some chow for the trip.â He trotted toward the airport cafeteria and returned a few minutes later with a bag of sandwiches and milk.

Soon the four companions were in the air, speeding toward Granton. They set down late that evening at an airport thirty miles from the town, rented a car, and started off. Fortunately, the speed limit was generous. Also, Granton had only one theater, which Frank found easily.

It was nearly time for the show to end. Frank parked the car across the street from the lighted marquee.

Joe walked down an alley to the rear and reported that there was only one other exit besides the front. âItâs on the side.â

âKeep a sharp lookout for Hexton and his men after the performance,â Frank instructed the others. âAlso, remember that they mustnât spot us or our chance to follow them might fail.â

Twenty minutes later the show ended and people spilled out through the doors. Presently a green sedan drove up in front of the theater.

âLook!â Joe said in a loud whisper. âThe driver is Stony Bleeker!â

Four men appeared from the alley exit. âThereâs Hexton!â Chet whispered.

âAnd Vordo with two short men!â Frank observed.

âThey look like twins!â Joe exclaimed.

âIâll bet thatâs how Hexton works the vanishing bit,â said Chet. âOne twin disappears in the box and the other appears from the wings! From the audience, who could tell they werenât the same man?â

The magician and his assistants got into the car and sped off. Frank and his companions followed at a safe distance. Several blocks farther on, the green car passed a high wall surrounding a garden back of a hotel, then pulled around the corner and stopped in front of the Granton Inn. The men got out and entered, while a doorman drove the car into the hotelâs underground garage.

Frank parked a short distance from the entrance. âLetâs stay out here and see what happens,â he said. âWeâll take turns keeping watch. Good thing there are no exits except to this street or the garden.â The foursome settled down for a long vigil.

As they waited, Joe noticed that Chet seemed preoccupied. His stout friend was staring at something high on the side of the hotel.

âWhat are you looking at?â Joe asked.

âThat window up there near the top. The room light is going on and off.â

The young sleuths watched the light for a time before noticing that it was following a definite pattern.

âDit-dit-dit dah-dah-dah dit-dit-dit,â mumbled Frank in tempo with the light.

âAn SOS!â Joe cried. âIn Morse code!â

âNo doubt about it!â Frank exclaimed. âMaybe itâs from Dad! He could be a prisoner in Hextonâs room!â

Throwing caution to the winds, the Hardys dashed into the hotel. Chet and Jack Wayne remained in the car to watch the exit. The desk clerk was startled when the boys rushed in.

âWhich is the Incredible Hextonâs room?â Frank asked.

The man automatically answered, âHeâs in Suite 924. What are your names? Iâll announce you.â

âNever mind,â Joe said.

âBut I have to announce all visitors,â the clerk insisted. âItâs a hotel rule.â

As he scooped up the house phone, Frank and Joe darted into an elevator. They burned with impatience while the car rose slowly. When it reached the ninth floor, the boys hopped out and rushed to Hextonâs suite. To their surprise, the door was partly open. On it hung a sign: DO NOT DISTURB.

âCareful!â Frank warned. âIt might be a trap.â

Cautiously they entered and hurriedly glanced into each of the rooms of the suite.

âNobody here!â Joe declared.

âThey were warned by the desk clerkâs call,â Frank said. âLetâs go after them! They must have escaped by a stairway.â

The boys ran along the corridor toward an exit sign and bounded down the staircase. Reaching the lobby, they asked the clerk if he had seen Hexton or his assistants pass through.

âIâve seen no one,â was the response. âWhatâs this all about?â

âNo time to tell you now,â Frank said. âHow do we get to the underground garage?â

âBy the elevator or the back stairs,â the clerk answered.

âQuick! Outside!â Frank shouted to Joe. âMaybe we can cut them off!â

They raced from the hotel and headed for the driveway leading to the underground garage. Just then the green sedan roared out.

âWatch it!â Joe yelled. They fell backward as the speeding car grazed their jackets. Scrambling to their feet, the boys ran for their own car. It was gone!

âChet and Jack must have recognized Hexton,â Frank surmised, âand followed him.â

He and Joe hurried back to the hotel to search the magicianâs rooms for clues.

âCome here!â Frank called softly to Joe as he opened the door to an adjoining bedroom. âThis is where the SOS was sent from!â The electrical plug to a lamp was only part way in the wall outlet.

âThe signal must have been sent by manipulating the plug,â Frank said.

âWhatâs that?â Joe exclaimed, pointing to something written near the base of the wall. The pair bent down to examine the faint scribbling. It read:

441810682300 Am all rightâ

âThatâs Dadâs writing!â Joe exclaimed. âHe was trying to tell us something!â

âThe âAm all rightâ is clear enough,â Frank remarked as he carefully studied the writing. âBut the numeralsâwhat do you make of them?â

Joe rubbed his chin thoughtfully. âNothingâyet. But Iâll bet theyâre mighty important.â

Frank took a notebook from his pocket and jotted down the cryptic message. The boys then went downstairs and walked out of the hotel just as Chet and Jack Wayne drove up.

âWe chased âem!â Chet said.

âAny luck?â Frank asked.

âNo! Only their license number. Lost âem in traffic,â Jack answered.

âBut,â Chet continued eagerly, âwe did get close enough to see that there were six men in the car.â

Frank nodded. âIâm sure the sixth was Dad!â

After phoning a description and the license number of the green car to the police, Jack and the boys decided to return to the theater.

âHexton must have left his stage equipment behind,â Frank said. âPerhaps he gave instructions where he wanted it sent.â

At the theater a local truck was parked near the side entrance.

âMaybe itâs waiting to pick up the gear,â Joe said.

âLetâs ask some questions,â Frank suggested.

Chet and Jack Wayne were instructed to keep an eye on the truck while the Hardys went inside. They confronted the theater manager just as he was locking his office, and asked him where Hextonâs equipment was to be taken.

âAs far as I know,â the man replied, âHexton made arrangements to have it stored in a local warehouse.â

âDid he leave anyone behind to dismantle and pack the stuff?â Frank inquired.

âYesâa man I never saw before. Said he had just arrived in town this morning,â the manager replied. âHexton took his four regular assistants with him.â

Â 

A shout came from the street and the boys rushed outside.

Chetâs face was flushed with excitement. âA man forced Jack into the truck and drove off! He had a gun!â Chet pointed down the street. âThere they gotâ

Frank and Joe caught a glimpse of the vehicle as it rounded a corner several blocks away. They grabbed Chetâs arms and dashed for their car!

CHAPTER V

Mysterious Rendezvous

FRANK jumped behind the wheel, the doors were slammed shut, and the car roared off in pursuit of Jack Wayneâs kidnapper! Seconds later, the headlights picked the truck out of the darkness on a road leading from the city.

âThe driver must know weâre after him,â Frank observed as the vehicle speeded up. âIâll try to head him off.â He bore down on the accelerator until the needle touched the speed limit.

âWeâre gaining!â Chet yelled. Gradually the car moved alongside the truck. Then, with a burst of power, it pulled ahead and in front.

âBe careful!â Joe pleaded. âThat truck could plow right through us!â

The two vehicles reeled back and forth across the road as Frank tried frantically to prevent the truck from pulling ahead of them.

âIf someone comes toward us from the opposite direction, weâve had it,â Chet mumbled as he wiped his forehead.

He relaxed a bit when the speedometer indicated less than forty miles per hour. Frank had noticed that the truck had suddenly slowed and begun to wobble violently.

âWhatâs happening?â Joe asked.

âLeaping mackerel!â Chet yelled. âJack and the driver are fighting! Oh, I hope that man doesnât shoot!â

He had hardly finished speaking when the truck skidded off the road. Crash! With a thud the heavy vehicle tumbled on its side into a shallow ditch, its wheels spinning.

Frank squealed to a stop. The boys leaped out and ran to the wreck, just as Jack Wayne pushed his door open.

âJack! You all right?â Frank panted.

âA little shaky, but this guyâs been kayoed.â

Jack climbed out and the others dragged the driver through the door. He regained consciousness a few moments later and weakly shook his head.

âWho are you?â Frank demanded.

âNone of your business,â the man muttered. He was tall and husky, with bulging muscles. He looked for his revolver, which now lay on the road.

âThe police will be interested to know you kidnapped Jack Wayne,â Joe said, pointing to the pilot.

âAll right!â the driver bellowed. âMy name is Burly Wilkes!â

âHow long have you been working for Hexton?â Frank asked.

âJust today. And I didnât try to kidnap anybody!â

âI suppose you just felt like taking our friend for a ride at pistol point,â Chet remarked scornfully.

âHexton hired me to take care of his equipment,â Wilkes said. âHe told me there were some guys trying to steal his stuff. When I saw your friend snooping around the truck, I thought he was one of âem. I just wanted to give him a scare.â

At that moment a police car arrived on the scene. An officer jumped out and walked toward them. âWhatâs going on here?â

When the boys explained, the officer took Wilkes into custody and requested that Jack Wayne follow him to police headquarters to file a complaint.

Further questioning of Wilkes by the police revealed nothing more than what he had already told the young detectives. Apparently, Frank reasoned, he was more afraid of Hexton than of being thrown into jail.

The Hardys and their companions checked in at a motel to get a little sleep. Early the next morning they flew back to Bayport. Chet said good-by and headed for the farm in his jalopy.

Mrs. Hardy and Aunt Gertrude were overjoyed to see Frank and Joe, and instantly asked about Mr. Hardy. They received a detailed report.

âIâm still fearful,â said the boysâ mother, âbut the news is somewhat encouraging. You say he wrote, âAm all rightââ?â

âYes,â Frank assured her.

Aunt Gertrude said in her forceful way, âThatâs enough for me. Iâm sure Fenton is a better magician than Hexton when it comes to escaping from traps. Heâll get out of those villainsâ clutches!â

âYouâre right,â Joe agreed. âJust the same, I think he needs our help.â

Directly after supper Frank and Joe went to their fatherâs study and tried to decipher the message scribbled on the hotel wall.

Joe read aloud, ââ441810682300.ââ

âIâm stymied,â Frank admitted. âThe numbers donât fit into any code Dadâs used with us before.â

âMaybe it isnât a code at all,â Joe suggested. âThe numbers might represent something else.â

Just then Chet arrived. He strolled into the study with a large silver bowl tucked under one arm. In his other hand he held a big square of blue silk.

âOkay, you masterminds! Give me your attention!â he demanded. âYou see standing before you the dean of sorcerers! The master of legerdemain! The worldâs most outstanding thaumaâthaumaâthaumaturgist!â

âWow!â Joe exclaimed. âListen to him! Youâd better get the dictionary, Frank!â

Chet placed the bowl on the desk as the Hardys watched in amusement. âYou are most fortunate,â he said, âsince you will see a private performance by the greatâthe incredibleâthe fantastic Morton!â

Chet paused, a faint smile curling his lips and added, âPerhaps you hadnât heard that Iâve been taking a mail-order course in magic!â

The Hardys looked unimpressed and said nothing. Chet eyed them with a smug expression. âWill you please bring me an egg, some relish, mustard, catsup, and perhaps some vinegar and water.â

âYes, master!â Joe left the study and returned shortly with the items. âHere you are.â He grinned. âAnd whatever you plan to do with them it had better be good. Aunt Gertrude almost took the broom to me for bringing this stuff.â

Ignoring Joeâs remark, the chubby youth continued with his spiel. âAll right! Prepare yourselves for the impossible!â he declared. âListen now to my weird and strange incantations! Utterances that will mystify the ages!â

The boys watched as Chet cracked the egg and dropped it into the bowl, shell and all. He added the vinegar, water, and other ingredients.

âWhat a crazy concoction!â Joe said as his chum stirred the mixture.

Chet covered the bowl with the silk cloth. âBrace yourselves for the most amazing feat of all time!â He began to pass his hands slowly over the bowl. âEzard, Kazard Mokim, Whumpf!â

âNow whatâ Frank asked.

âAh!â Chet announced. âYou have just witnessed an astounding display of my mystical powers! The ingredients in this bowl have vanished. Puhff! Just like that!â

âOkay, Merlin,â Joe said, laughing. âProve it. Uncover the bowl.â

âYou doubt my magical skills?â Chet said. âI wonât just uncover the bowlâIâll go a step further to prove my powers.â He placed the bowl on his head upside down.

âThere! You see, Iââ He stopped short as its contents flowed over his head and face. Some spattered on the floor. âOh, ugh!â

The Hardys howled with laughter. âYouâd better clean up that mess fast,â Frank warned. âIf Aunt Gertrude sees it sheâll cause you to vanish. Puhff! Just like that!â

Frank and Joe howled with laughter

Joe rushed out of the study and returned with an armful of paper towels. It took considerable rubbing before Chet became recognizable again and the carpet clean.

âI canât understand,â he murmured. âThe book said it would work!â

Joe chuckled. âMaybe you got your incantations mixed.â

âAnyway, I was just trying to cheer you fellows up,â Chet mumbled.

âWe appreciate that,â Frank said. âBut how about less spectacular tricks for a while?â

At a loss for words, Chet sat down in an armchair and examined his silver bowl.

The ringing of the telephone broke the silence in the study. Frank took the call. âFrank Hardy speaking.â

âIf you and your brother want to see your father,â said a muffled voice, âcome to the old Landon Mansion in an hour. And come alone!â

âWho is this?â Frank demanded. There was a sharp clicking sound. The mysterious caller had hung up!

The message startled the boys. âDid you recognize the voice?â Joe asked.

âIâm not sure,â Frank said, âbut it sounded like Hextonâs giant helper, Vordolâ

âThe Landon Mansion, eh?â Joe queried. âThat old dilapidated house hasnât been lived in for years. I understand itâll be torn down soon.â

âIf I remember correctly, itâs just off Highway 18,â Frank recalled. âItâll take us about thirty minutes to drive there.â

âBut it may be a trap!â Joe declared.

âWe must take the risk,â Frank insisted. âDad really might be there.â

They asked Chet to post himself at the telephone. âIf weâre not back in two hours, notify the police,â Frank requested.

He and Joe stopped to tell Mrs. Hardy their plans. Though worried, she conceded they should go. Ten minutes later the Hardysâ car was humming down the highway on the outskirts of town. The night was clear and a strong breeze lent a chill to the air. A full moon bathed the trees and fields in an eerie, silvery light.

Before long, the Hardys came to a narrow dirt road and turned onto it. Neglected for many years, it was pitted with holes and covered in spots with clumps of grass and weeds. There were signs, however, that some kind of vehicle had traveled the road recently. Much of the grass had been flattened and there were tire tracks.

At the end of the rutted road, the two sleuths discovered iron gateposts. The gates had long since fallen from their rusted hinges. In the distance stood the Landon Mansion, ghostly in the moonlight. Frank and Joe got out of the car and walked toward it. The only light came from a window on the second floor.

Reaching the house, they stopped and listened for a moment. All was quiet.

The Hardys furtively made their way to the door and eased it open. Silently they slipped in, but froze like statues when Vordoâs voice boomed from upstairs.

âYour fatherâs waiting here!â

Frank and Joe broke into a cold sweat. âThat guy must have radar eyes,â Frank whispered. âCome on, Joe! We canât turn back now.â

The boys climbed the creaky staircase, which groaned under their feet. Just before they reached the top, a grinding sound echoed through the old building. With a splintering crash the staircase parted just where they were standing. The lower section fell away and the boys plunged toward the darkness below!

CHAPTER VI

Aerial Chase

FALLING, Frank made a grab for the step ahead of him and hung on as Joe gripped his waist. Though his arms ached from the strain, Frank pulled desperately, hoisting himself up inch by inch.

Finally Joe reached out and grasped the step. After much effort, both boys worked themselves safely onto the next tread.

âThese guys donât play around,â Frank murmured, rubbing his swollen hands. âWell, up we go.â

They climbed the few remaining steps and entered the room straight ahead. It was empty, except for a small table, on which a single candle burned.

At the end of the room was a window. The boys rushed to it and looked down into the yard in time to see Vordo and Stony Bleeker leap into a car and speed off.

âNeat getaway,â Joe muttered.

âNo use trying to chase them,â Frank said. âTheyâll be out of sight by the time we get to our car.â

âDad wasnât with them,â Joe commented.

âOf course not. Calling us over here was just a trap,â Frank replied. He pulled angrily on the rope which Vordo and Bleeker had used to get from the window to the ground.

The boys went to examine the remaining section of the staircase. It had been sawed more than halfway through! In a sober mood Frank and Joe returned to the window, slid down the rope, then drove home. Chet was greatly relieved to see his friends.

âWhat about your dad?â he asked excitedly, and was quickly told what had happened.

âWow! Well, Iâm glad youâre safe,â Chet said. âWhile you were gone two important phone calls came in. The first was from the police chief in Granton. He said Burly Wilkes has escaped!â

âWhat!â Joe exclaimed. âHow did that happen?â

âA detective had handcuffed Wilkes to a table in the interrogation room while he went out for a few minutes,â Chet said. âWhen he returned, Wilkes was gone. Somehow, he had slipped out of the handcuffs.â

âA trick he could have learned from Hexton,â Frank mused.

âAnd another thing,â Chet went on, âthe green sedan was Hextonâs and it has not been picked up.â

âWhat about the second call?â

âIt was from Kenneth Dell,â Chet answered. âHe wants to talk to you as soon as possible.â

Frank picked up the phone and dialed the private number of the Great Circle Airwaysâ security chief.

Dell sounded excited. âIâve had a report that one of our flight stewards, named Timken, has been acting suspicious lately. He used to be friendly and stay around for a while after landing. Now shortly after he gets in from Scotland on Flight 101, he leaves in a waiting helioplane. He never says where heâs going.â

âThat is strange,â Frank remarked. âA helioplane! The kind that can take off and land in short distances?â

âRight! It can also fly at very low speeds.â

âHave you any idea where the steward goes?â Frank asked.

âNo flight plan was filed,â Dell said.

âWho owns the plane?â Joe inquired.

âI donât know, but now I mean to find out,â Dell replied. âWhenever the pilot has asked for landing instructions, he has identified himself as âHelioplane 345.â Of course those are only the last three figures in his whole number.â

Joe asked, âWhat about Timken as a steward?â

âHe was hired by our firm only a couple of months ago. Seems efficient and so far we havenât found anything incriminating in his record. Flight 101 is part of his regular schedule, and Iâm watching it for anything the least bit suspicious. With Hextonâs headquarters probably in a Scottish castle, we canât be too careful about our Scotland flights.â

âI have an idea,â said Frank. âThe next time Timken takes the helioplane, Joe and I will follow him.â

âFollow him?â Dell said. âHow?â

âIn Dadâs plane.â

âBut if you were to take off immediately behind the helioplane and trail it on the same course,â Dell countered, âwouldnât that arouse the pilotâs suspicions?â

âWe would take off from a different airport,â Frank said. âHold on just a minute, will you?â

He beckoned Joe, who handed him an aeronautical chart. Spreading it out, Frank examined the area in the vicinity of Great Circleâs base. Then he picked up the phone again.

âThereâs a small general airfield at Burnsbie near your base,â he told Dell. âWeâll land there and wait. When you see the steward boarding the helioplane, let us know.â

âIt might just work at that,â the SKOOL agent agreed.

âWhat is Timkenâs first name and when is he scheduled to return from his next flight?â Frank asked.

âStand by. Iâll check the crew schedule.â There was a brief pause, then Dell came on again. âHis first name is Guy, and heâs scheduled for an outgoing flight tonight. Heâll be back here at ten oâclock Thursday morning, our time.â

âGood!â Frank said. âBarring bad weather, weâll plan to be at the field at least an hour before Timken is due back.â

Frank said good-by, then called Jack Wayne and informed him of the plan. The pilot said he would have the plane fueled and ready to fly Thursday morning at the crack of dawn.

As the first rays of sunlight appeared in the east that day, the Hardys got up and dressed. They were surprised to find their mother and Aunt Gertrude already in the kitchen preparing breakfast for them.

âUm! Sausage and cakes!â Joe said with a grin.

Immediately after breakfast, the boys drove to Bayport Airport. There they made a final check on the weather. The forecaster told them it would be CAVU-Geiling and Visibility Unlimitedâfor at least another forty-eight hours.

âThe shipâs all set to fly!â Jack Wayne called as they walked across the ramp.

He and the Hardys got into the plane and fastened their seat belts. A sudden roar echoed across the field as Jack started engines. He made a quick but thorough check of the instruments. Minutes later, they were airborne and climbing rapidly above Bayport.

âWe should get to Burnsbie with plenty of time to spare,â Frank said as he glanced at his watch.

Upon arriving at their destination, Jack at tended to the refueling of the plane, while Frank and Joe waited in the operations room for a call from Kenneth Dell.

It was a few minutes after ten oâclock when the telephone rang. The airport manager scooped up the receiver, then announced that the call was for the boys.

âThis is Kenneth Dell, Frank! Timken just got into the helioplane. Theyâre taxiing out now for take-off.â

âRoger!â declared the young detective. âWeâre on our way.â

In a matter of minutes, Jack Wayne and the Hardys were approaching Great Circleâs base at several thousand feet.

âThereâs the helioplane!â Joe exclaimed. âItâs at the three-oâclock position.â

The craft veered slightly to a northeast course. Jack followed at a safe distance.

A short time later the helioplane made two complete turns, then reverted to course. Jack did the same. Moments later, their quarry repeated the maneuver.

âWhy all those turns?â Joe asked.

âHeâs probably checking to see if heâs being followed,â Jack replied.

âDo you suppose he spotted us?â Joe asked.

Frank replied, âNo doubt. But weâve nothing to lose by continuing the chase.â

The gap between the two crafts, however, decreased more and more as the helioplane reduced speed.

âThat clunker up ahead can fly much slower than we can.â Jackâs voice showed concern.

He attempted to keep his distance, but another glance at the airspeed indicator told him that their plane was dangerously near to a stall. The Hardys tightened their seat belts when the craft began to buffet.

âSorry, boys,â the pilot said. âI canât make it.â He was about to increase power when suddenly the helioplane executed a sharp turn and headed directly for them. Jack quickly maneuvered out of the way, but the sharp movement of the controls caused the aircraft to stall.

The plane rolled into an almost inverted position and dived vertically toward the ground!

CHAPTER VII

Suspect on the Run

FRANK and Joe were thrown against their seat belts as the plane dropped earthward, and the wind whistled an eerie dirge against the wings.

âHang on!â Jack shouted as he pulled the throttle closed and applied aileron and rudder control.

He managed to level the wings, then concentrated on recovering from the steep dive. As he eased back slowly on the wheel, the boys were pressed down into their seats by the increasing G force.

Finally Jack had the aircraft back to straight and levelâbut with not much altitude to spare. He increased power and the plane climbed higher. For a moment nobody spoke.

âWhew!â Joe finally exclaimed as he wiped perspiration from his face. âI canât say Iâm too keen on this kind of maneuver.â

âWhoever is flying that helioplane,â Jack Wayne remarked, âis a pretty good pilot.â

âKeep a sharp lookout,â Frank urged as he searched the sky above them.

They continued to gain altitude and the boys scanned the area on all sides. Ahead, puffy white cumulus clouds built up over the hilly terrain.

âIâm afraid weâve lost our quarry,â the pilot said. âAnd Iâll bet theyâre members of UGLI!â

âYes, worse luck,â Frank answered. âThe clouds offer excellent cover. Trying to find those agents in it would be like trying to find a flea in a fog.â

The Hardys decided to discontinue the chase and return to Great Circleâs base. Upon landing, an announcement came over the public-address system.

âFrank and Joe Hardy, please report to the operations room.â

The young sleuths sprinted to the administration building. In the operations room Kenneth Dell was clutching a telephone to his ear.

âWhatâs up?â Frank asked.

âFlight Service has just given me the helioplaneâs full registration number. I told them to let me know if they heard anything from the pilot,â Dell said. âLooks as if weâre in luck! He ran into bad weather north of here, and had to file an instrument flight plan.â

âWhatâs his destination?â Joe asked.

âLogan International Airport, Boston,â the security chief replied.

âJeepers!â Joe exclaimed. âDo you think thatâs where he was headed all the time?â

âI doubt it,â Frank replied. âTimken wouldnât want anyone to know where heâs going. I think theyâre just planning to land and wait for the weather to clear. Then they can continue the trip without a flight plan.â

Dell signaled for silence as he pressed the receiver closer to his ear. He jotted down a few notes and then hung up.

âHereâs something else,â he announced. âThe pilotâs name given on the flight plan is Mazer. And the owner of the helioplane is the Coastal Courier Service.â

âSay,â Joe spoke up, âwhy donât we have Jack fly us to Boston right away? Logan is a busy airport. Timken might not notice our arrival.â

âGood idea,â Dell said. âIn the meantime, Iâm going to check out this information.â

An hour and a half later Jack Wayne and the boys were cleared for an ILS approach at Logan International Airport.

âLooks as if the weatherâs beginning to improve,â Jack remarked as they taxied to the parking ramp.

âI donât see the helioplane anywhere,â Joe observed.

âWeâll check with operations,â Frank said.

The boys hurried into the administration building. They located the operations manager and inquired about the helioplane.

âWhy, yes,â he said. âI remember the craft distinctly. It caught my eye, since that kind of thing is a rarity around here.â

âWhere is it now?â Joe asked.

âI think it took off about thirty minutes ago,â the operations manager replied. âBut why donât you check with the control tower?â He pointed to a wall telephone. âThatâs a direct line.â

Frank picked up the phone.

âLogan Tower! Stigand speaking!â crackled from the receiver.

Frank said, âA helioplane departed from here about half an hour ago. Can you tell me its destination?â

âStand by!â

There were a few seconds of silence, then Stigand reported, âThe pilot filed an instrument flight plan for Concord Airport, New Hampshire. However, he broke into clear weather at Manchester and canceled his flight plan.â

âThank you,â Frank replied, dejected.

âSo weâve lost them again,â Joe remarked.

âTimken and his pilot played it smart,â Frank said. âThey knew theyâd fly into clear weather. Iâll bet they never had any intention of landing at Concord.â

Just then two men approached the youths.

âWhatâs your interest in the helioplane?â one of them demanded.

âWho are you?â Joe retorted.

âWeâre detectives! Boston Police Department!â They flashed their badges.

âMy name is Amory,â one said. He pointed to his partner. âAnd this is Detective Sergeant Doran.â

Frank introduced himself and his companions.

âHardy!â Amory exclaimed. âAny relation to Fenton Hardy the private detective?â

âWeâre his sons,â Joe answered.

âWhy did you ask us about our interest in the helioplane?â Frank inquired.

âA couple of hours ago a local jeweler was approached by a fellow who tried to sell him a diamond. When the jeweler began to question him as to where he got it, the guy walked out. The jeweler became suspicious and called us.â

âWhat started you looking for this man at the airport?â Joe asked.

Amory replied, âThe jeweler said he was wearing a Great Circle Airways uniform. So the airport seemed a logical place to begin a search, although Great Circle doesnât come in here. We want to ask that fellow a few questions.â

âHeâs gone,â Frank said. âThe man youâre looking for is the same one weâve been following. He took off in the helioplane about half an hour ago.â

âThat adds up,â Doran commented. âThe operations manager told us a fellow answering the jewelerâs description had already left.â

âWe approached you boys,â Ames added, âbecause we heard you inquiring on the phone about the helioplane.â

There was little more the young sleuths could do, so they took off. During the return flight to Bayport, they mulled over the latest event.

âWhat do you make of Timken trying to peddle a diamond?â Joe asked.

âIt sounds to me like an attempt to get rid of stolen goods,â Frank concluded.

âCould be,â Joe said thoughtfully. âYou remember Dadâs report said that Hextonâs gang were robbers. If Timken is one of them, he may be smuggling in jewels stolen overseas and disposing of them here.â

Frank agreed. âBut UGLIâs business is espionage. I doubt if they would become involved in jewel robberies. On the other hand, Hexton and his gang might be playing the two games at once.â

When the boys arrived home, Frank at once telephoned their suspicions to Kenneth Dell.

âYou have a good theory there,â Great Circleâs security chief said. âIâm going to call Scotland Yard and inquire about recent jewel robberies.â He promised to get in touch later.

After Frank hung up the phone, he stood silent for a moment. âNext we must figure out that message Dad left on the hotel wall,â he told Joe.

Again they examined the row of numerals: 441810682300. But after more than an hour of attempting to decipher them, Joe gave a sigh of frustration. âIt doesnât make any more sense to me now than when we first started,â he admitted.

âIf this is a code, itâs a real puzzler,â Frank agreed. âBut weâve got to crack it!â

When Mrs. Hardy announced that dinner was ready, the boys reluctantly interrupted their task. They ate quickly, then went right back to the message.

Frank stared at it. âNeither the substitution nor transposition ciphers jibe.â

The young detectives worked late into the night. Exhausted, they finally went to bed.

Early the next day Frank and Joe continued to study the message, but all their efforts to decipher it ended in failure.

Shortly after ten oâclock Chet arrived at the Hardysâ home. He plodded up the stairs to the detectiveâs study.

âYouâre too late for breakfast, chum,â Frank said with a grin.

âAw, cut it out,â Chet mumbled. âAnyway, I stopped at Biff Hooperâs house before I came here. His mother was baking the most delicious pancakes I ever saw, with sausages and all the trimmings.â

âGlad to hear that,â Joe said jokingly. âWe wouldnât want to see you fade away.â

âHow is Biff?â Frank inquired as he glanced at his friend. Biff Hooper was a schoolmate of the boys at Bayport High.

âHeâs just fine. I wanted to show him a couple of my magic tricks.â

âDonât tell us you took that silver bowl of yours along?â Joe asked.

âNo, thatâs old stuff,â Chet retorted. âMy new tricks are more sophisticated.â

âOh yeah!â said Joe, chuckling.

âGo ahead and laugh if you want to,â Chet continued indignantly. âAt least Biff appreciated the great latitude of my genius.â

At Chetâs remark, Frank sat bolt upright in his chair.

âWhatâs the matter?â Chet asked, startled.

âWould you repeat what you just said?â Frank asked excitedly.

âYou mean about Biffâs appreciating the latitude of my genius?â

Frank sprang up. âThe key! Youâve given me the key!â

CHAPTER VIII

Sailing Sleuths

CHET looked confused. âWhat key? I donât see any key,â he said, glancing around.

âYou mentioned latitude! That must be itâlatitude and longitude!â Frank pointed to the numerals in the mystery message.

âI still donât get it,â said Chet.

Frank explained. âNotice that there are a total of twelve digits. The first sixâ441810âmust mean 44 degrees, 18 minutes, 10 seconds of latitude. The remaining figuresâ682300âwould then stand for 68 degrees, 23 minutes, 00 seconds of longitude â

âYouâre right!â Joe exclaimed.

Frank riffled through a stack of maps and selected one showing the Atlantic seaboard. âThose coordinates would locate a position in the area covered by this map.â

âHold on!â Joe said as he glanced at a chart of the world that he had just unfolded. âThe message doesnât specify whether the latitude is east or west, or the longitude north or south. Therefore, these coordinates might designate a location in Asia, the southern tip of South America, or the middle of the Indian Ocean.â

âTrue,â Frank agreed. âBut since Dad didnât make that clear in the message, Iâm certain he means the position is in our own hemisphere.â

He marked the spot on his map indicated by the coordinates. It was about eighteen miles off the northeast coast of the United States.

âBut thatâs a spot in the Atlantic Ocean!â Joe exclaimed.

Frank pulled out a nautical chart. It was on a smaller scale and showed more detail. Replotting the position, he discovered several small islets in the vicinityâso small they did not have names. The latitude and longitude coordinates lay directly over one.

âEureka!â Joe exclaimed. âIt looks as if weâre onto something! My guess is one of two possibilitiesâeither the place is UGLIâs headquarters for the U.S., or else itâs where Dad was taken.â

âMaybe itâs both,â Joe added. âWeâd better make a trip to that island!â

âWhat about me?â Chet demanded. âCan I come, too? After all, I found the key!â

Frank bowed toward his chum. âItâll be a pleasure to have you along, genius,â he said. âWe might need your help.â Then he walked to the telephone. âIâll call Jack and tell him to have the plane ready tomorrow morning.â

When Frank told the pilot their destination, Jack assured him there were several aviation radio facilities in the vicinity that would permit them to pinpoint the islet from the air.

Early the following day the Hardys, Chet, and Jack were winging their way toward the mystery spot. Soon they paralleled the Atlantic coast.

âHow long do you estimate itâll take us to reach the place?â Frank asked Jack.

The pilot checked the bearings indicated by the radio compass and omni-navigation receiver, then thumbed his small computer. âIâd say about thirty minutes from our present position.â

The boys gazed below. Ocean waves broke against the craggy coastline, tracing it with a ribbon of white foam that stretched as far as the eye could see.

As they passed over a small sailboat, Joe took out binoculars and scanned the area below. âLittle islands ahead,â he announced, and soon the others made out small sprinkles of land dot-ting the surface of the water.

âAccording to the cross bearings I calculated,â Jack announced, âwe should be over the place you want within one minute.â

âAnd what exactly are we looking for?â Chet queried.

âI donât know,â Frank answered. âBut ifââ

âHey!â Joe interrupted. âI see a lighthouse on that islet just below us.â

Frank took the binoculars. âYouâre right. It appears to be abandoned, but there are several cylindrical-shaped objects just to the left of the lighthouse.â

Jack took the plane to a lower altitude and Frank readjusted the glasses. âThey look like drums of oil, or gasoline,â he said.

âBut for what?â Joe questioned. âA boat? Certainly couldnât be for an airplane.â

The pilot asked for the binoculars and studied the islet. âThe surface is level enough for a plane,â he observed, âbut itâs much too short to be used as a runwayâthat is, except for a helicopter, or perhaps a helioplane!â

Frank and Joe glanced at each other. Could there be a connection between the islet and the helioplane in which Timken had eluded them?

Frank suggested they fly back to the coast and land at the nearest airport. âI want to find out about the islet,â he said.

Jack found a small field not far inland and set the plane down. The Hardys hopped out and hastened to the operations shack. There they met a solid, middle-aged man with a shock of gray hair, who introduced himself as Ty Carter, the owner of the airport.

âI donât know much about that islet with the abandoned lighthouse,â Carter told them, âexcept that it is private property. It was sold at auction recently.â

âHave you any idea who bought it?â Joe asked.

âFellow named Bodkins. Heâs not from around here so I canât tell you anything about him.â

âBodkins?â Frank thought. A possibility struck him. âCould this be an alias of Hextonâs?â Aloud he questioned, âHave you ever seen a helioplane in the vicinity of the islet?â

âFunny you should mention that,â Carter replied. âDuring the past couple of weeks I saw one headed in that direction several times. But whether it was going to the islet or not, I wouldnât know.â

The boys thanked the man for his cooperation, then returned to the plane.

âFellows,â Frank said suddenly, âI have an idea. Why donât we rent a boat and look at the place?â

âWhat if Hexton and his men are on the islet?â Chet asked.

âThatâs a chance weâll have to take.â

After lunch Jack remained with the plane, while Chet and the Hardys hiked to the nearby coastal town. They found a boat-rental place, but unfortunately all the power craft were in use. Frank finally selected a small jib-headed racer.

He manned the helm while Joe and Chet hauled the sails to the top of the mast. A strong breeze carried them quickly away from the dock. Nearly three hours passed before the islet appeared off the port bow of their craft.

âSeems deserted,â Joe said.

Frank manipulated the helm to direct the boat in a wide circle around the tiny point of land. From the other side of the islet a fast powerboat appeared.

When it drew closer, Joe exclaimed, âThatâs Stony Bleeker at the wheel! And Vordoâs with him. They must have spotted us!â

âThe boatâs going to ram ours!â Chet shouted as the craft headed directly for the sailboat.

Frank applied hard helm and changed course quickly. The powerboat missed the stern by a few inches and threw a heavy spray of water over the boys. Its wake rocked the sailboat violently.

âHold fast!â Frank cried out. âStay in the center, fellows, or weâll capsize!â

âLook!â Joe yelled. âTheyâve turned and theyâre coming at us again!â

As the powerboat sped perilously close, more water foamed over the gunwales.

âWe canât stay upright much longer!â Joe shouted.

The next pass by the powerboat was so close that the two craft sideswiped. The boys hung on, but plunged into the sea an instant later as the sailboat went over on its side.

Vordo burst into wild laughter. Stony was so preoccupied watching the boys come to the surface he failed to notice that he was steering directly toward the islet.

âWatch out!â Vordo bellowed at him.

Bleeker made a desperate, last-minute effort to turn away. Too late!

Crash!

The powerboatâs momentum carried it onto the craggy shore, and a sharp rock ripped through its hull.

The men leaped out. Furious, they shook their fists. âWeâll get you for this!â Vordo thundered at the three boys, who now lay across the half-overturned hull of the sailboat.

âNow what?â Chet asked.

Frank and Joe were glumly silent. They knew that trying to right their boat with its water-soaked sails would be next to impossible and the only haven within swimming distance was the islet!

CHAPTER IX

The Lighthouse Prison

IN a split second Frank had made up his mind. âQuick!â he shouted. âHelp me haul in the main-sail! Itâs our best bet.â

Joe unfastened the lanyard while the other two with great effort pulled the top of the partially submerged sail down the mast. When they had it tightly lashed around the boom, the boys secured the working jib.

âJumping catfish!â Chet yelled in alarm. âWeâre drifting closer to the islet!â

While he and Joe watched the movements of Vordo and Bleeker, Frank swam to the other side of the boat. He put his weight against the bottom of the keel and tried to force it downward into the water.

âPush up hard on the mast!â he shouted to Joe and Chet.

The power of their combined efforts started to rotate the sailboat.

âHarder!â Frank yelled. âPush up harder!â

Suddenly the boat rolled to an upright position. Frank reached for a hand bail-out pump clamped against the inside of the hull. Working frantically, he pumped the water out of the boat. Then he flung himself over the gunwales, followed by Joe and Chet.

âTheyâre taking off!â Vordo bellowed to Bleeker. âAfter âem!â

The two men plunged into the water and swam toward the three boys.

âUp with the sails!â Frank commanded. âIâll take the helm.â

Joe and Chet hoisted the sails into place. A strong breeze caught them and began pushing the boat ahead. Frank turned the craft sharply away from the islet.

Vordo screamed at them furiously, âStop!â

âHe seems to be the excitable type,â Chet said, weak with relief, as they went speeding back toward the mainland.

âWe certainly didnât win that battle,â Joe observed wryly. âWeâre retreating.â

Frank nodded. âWeâll have to find another way to get here, and fast,â he declared. âIf Dadâs a prisoner in the lighthouse, theyâll probably move him out as quickly as they can.â

The boat had covered nearly half the distance to the mainland when the sails became almost limp.

âThe wind is dying down,â Joe said, alarmed. âWeâre barely moving.â

Gradually the breeze subsided to a complete calm. The sailboat ceased to move ahead and rocked gently with the waves. Frank grabbed a paddle that was clamped under the gunwale. âGuess weâll have to get back the hard way.â

âItâll take us all night at this rate!â Chet exclaimed. âThere canât be much more than another hour or so of daylight.â

âWe have no choice,â Frank said. âLetâs take turns paddling.â

Chetâs prediction proved to be right. It was well into the night before they could see the vague outline of docks strung along the coast.

Presently they heard the put-put of an outboard motor and a bright beam of light swept the surface of water ahead. As the boat drew closer, they recognized the pilot as the man who had rented them the sailboat.

âHey!â he shouted. âYou said you wanted the boat for the day, not for the night!â

âRight.â Frank grinned. âWe were becalmed. How about giving us a tow to your dock?â

The man threw them a line and went on, âIâve been searching for you guys since dark. In an hour I was going to notify the Coast Guard.â

âIâm sorry,â Frank said.

When they reached land, the boatman saw that the youths were totally exhausted. âI have extra bunks in my shack,â he said. âItâll be daylight in another couple of hours. Why donât you lads eat a bite, then get some sleep?â The boys accepted his offer gratefully.

Before turning in, Frank called the airport and asked to speak to Jack.

âI was worried about you fellows,â the pilot said with deep concern. âIâve been waiting here in the operations shack, wondering what happened. I almost notified the police.â

Frank told him of the dayâs adventure, then suggested that they meet in the morning for breakfast.

It was five oâclock when Frank was awakened by the sound of a motor. He climbed from his bunk and peered out the window. What he saw caused him to snap wide awake. Vordo and Bleeker in their powerboat! âThey must have made temporary repairs,â he thought.

Frank awakened his companions. âWh-whatâs the matter?â Chet mumbled, rubbing his eyes.

âLook!â Frank said, pointing to the boat. It was just docking at a pier where a sign read: CLARKâS BOAT REPAIRS.

âThatâs it!â Joe declared. âTheyâre having the hull fixed.â An idea flashed through his mind. âNow would be a good time to return to the islet!â

âDonât tell me weâre going to paddle ourselves all the way,â Chet complained.

âWeâll rent a motorboat,â Frank said. He made arrangements for the craft, then telephoned the airport and explained his plan to Jack. âVordo and Stony Bleeker just arrived with their damaged powerboat. Itâs docked at Clarkâs Boat Repair place. Could you rent a car, drive down here, and keep an eye on those two? If they should start back to the islet before we return, fly out and warn us by making a low pass. If they start to leave town, notify the authorities.â

âWilco!â the pilot replied. âIâll get going right away.â

When the boys went to the dock, the owner said, âFellows, Iâve just learned by radio thereâs some bad weather in storeâa norâeaster.â He pointed toward a darkening ridge of clouds far off on the horizon. âYou can see it stirring up already.â

âBut this is important!â Frank insisted.

The boatman pondered for a moment. âWell, if you promise to keep a sharp eye to the weather and to pull into land if it starts blowing too much, I guess you can have a boat.â

The boys thanked him and after a quick breakfast started out to the islet. The trip took less than half the time it had required in the sailboat. Nevertheless, when the lighthouse came into view, the sky had grown dark and the howling wind had developed into gale force.

âA hurricane!â Chet cried out.

Torrential rain burst upon the boys and the boat was tossed around like a cork in the heavy seas. But Frank skillfully kept it headed for the islet and finally maneuvered close to shore.

Joe tied the mooring line around his waist and leaped into the water. He swam hard to the craggy shore and soon had the boat on solid ground.

âWhew!â Chet groaned. âItâs going to take me a month to dry out.â

The boys peered through the sweeping sheets of rain at the lighthouse. Frank signaled his companions to be silent as they crept toward a lighted window near the base of the structure. Peering inside, they saw a man seated at a table.

âBurly Wilkes!â Joe whispered.

âHeâs alone,â Frank observed. âThatâs a break for us.â

âBut what about Dad?â Joe asked.

âIf theyâre holding him prisoner here,â Frank said, âheâs in another room.â

âLet me take a look,â Chet suggested, and stretched higher for a glimpse inside. He slipped on a rock and banged his head against the glass. Burly Wilkes whirled around.

âHide!â Frank ordered.

As Wilkes stomped to the window, the boys flattened themselves against the wall. Apparently satisfied nothing was wrong, he returned to his chair.

âA hurricane!â Chet cried out

âThat was close,â Joe commented.

âSorry,â Chet mumbled sheepishly. âNow what?â

Frank whispered a plan. âWeâll break in and take Wilkes by surprise. When I give the signal, hit the door with all youâve got.â

The boys positioned themselves. Frank raised his hand slowly, then dropped it. The three threw themselves against the door and it burst open. Wilkes jumped up from his chair, too startled to utter a cry.

âStay where you are!â Frank commanded.

But Wilkes, recognizing the Hardys, bolted for a staircase which spiraled up to the top of the lighthouse. The boys raced after him.

Reaching the top, Wilkes rushed through a doorway and started to swing the metal door closed behind him. But Joe managed to prevent it from slamming shut by jumping into the narrow opening.

âThere he goes!â Chet shouted as he spotted Wilkes running out onto a catwalk encircling the top of the structure.

Finally the fugitive could go no farther. He was trapped and turned to face his pursuers. He threw a punch but missed. Frank countered with a blow to the stomach that sent the man sprawling. In a flash, Joe and Chet were on him and Wilkes was pinned helplessly to the metal grating of the catwalk.

âLet go of me!â he screeched.

Frank motioned the other two off, then dragged the man to his feet. âHexton kidnapped our father, didnât he?â

âYes. But I had nothing to do with it!â

âWhere are they keeping him?â

âHe was here.â

âWas?â

âWell, heâs gone!â

âWhere?â

âI donât know. Mr. Hardy escaped more than five days ago. Those SKOOL men are pretty smart!â

CHAPTER X

Wing Signal

THE boys were dumfounded. âWhat do you mean our dad escaped?â Joe asked. âHow?â

âI donât know. I wasnât here.â

Frank believed that Wilkes was telling the truth. But where could their father be? And why hadnât he been in touch with them?

The Hardys tied Wilkes securely to a chair. Then Frank, Joe, and Chet settled down to wait out the storm.

While the wind and rain beat against the lighthouse, Frank and Joe questioned Wilkes further. Their prisoner said he did not know the whereabouts of Hexton, nor just what sort of an operation he was running.

âIâm a new man in the outfit. The magician hasnât taken me into his confidence,â he added.

âSo youâre just learning the UGLI business,â Frank remarked. Wilkes nodded.

He admitted that the metal drums which the Hardys had spotted contained airplane fuel, but now were empty. This was confirmed by Joeâs thorough search as soon as the rain subsided and the sun burst through the broken clouds.

âOkay, Wilkes,â Frank said tersely when his brother returned. âYou told the truth about the drums. What about the helioplane?â

The manâs jaw dropped. âWh-whatâd you meanâhelioplane?â

âYou know all right!â Joe said. âSo far, weâve made things easy for you, Wilkes, but if you donât tell the whole story, weâll have you charged as an accomplice to a kidnapping!â

âNo, no!â he whined, blanching a sickly white.

âI saw the plane land here twice. Both times it stayed a few minutes, then took off again.â

âWere there any passengers aboard?â

âJust one guy wearing some kind of uniform.â The man began to perspire freely. âHexton will kill me if he finds out I told you.â

âDonât worry about him,â Chet said. âThe Hardys will take care of that crooked magician.â

Just then they heard an airplane and rushed outside. Looking up, they saw their own plane coming in from the west. It dived and made a low pass over the islet âThe signal!â Frank exclaimed. âVordo and Bleeker must be on their way back!â

âLetâs wait and nab âem,â Joe suggested.

Frank was about to answer when Jack Wayne headed in toward the islet again. He made another low pass, but this time the boys saw a small object drop from the plane. It bounced along the rocky surface and rolled to a stop close by. It was a metal box with a message inside:

Vordo and Bleeker on way back! Have two other men with them. Believe they are armed. Suggest you leave immediately. Head north before turning toward mainland to avoid their boat.

âLetâs get out of here fast!â Chet said.

âI donât like the idea of running,â Frank said, âbut the odds are against us. Weâll go back to the mainland and notify the police.â

Pushing the reluctant Wilkes before them, the boys hastened to their motorboat. Luckily it was undamaged by the storm. A quick check of the fuel, however, showed they could not take the northerly course Jack had suggested.

âWe have just enough gas to make shore,â Frank announced.

âWhat about Vordo and his men?â Chet asked.

âMaybe weâll be able to slip by without their noticing us,â Frank answered.

Wilkes became arrogant at hearing that his cohorts were on their way back. âYouâd better leave me behind if you know whatâs good for you,â he growled.

âNothing doing,â Joe retorted angrily. âAnd donât try to attract the attention of your buddies. Iâm sure theyâd reward you for having talked,â he added sarcastically.

This frightened Wilkes. He slumped down.

While Jack circled overhead, the boys made a beeline for the coast. A little more than half an hour had passed, when Jack throttled the engines on and off several times.

âIs he having trouble?â Chet asked.

The pilot gunned the engines again.

âNo!â Joe exclaimed. âHeâs signaling us!â Joe pointed to a small object in the distance, moving across the water. âThat must be Vordo!â

Frank quickly turned the motorboat onto a different course as the approaching boat drew steadily closer. In it were four men. The pilot, a tall, massive fellow, was unmistakably Vordo. He was steering directly toward the boysâ boat.

âTheyâve seen us!â Joe cried.

Frank attempted some evasive maneuvers, while still heading for the mainland. But the other boat was faster. Although Frank spun his wheel sharply in a series of turns to port and starboard, their pursuers continued to gain.

Finally Vordo bore down, but as he did, Frank pointed skyward and yelled, âLook up there!â

Jack roared down in a screaming dive and pulled out directly in front of the powerboat. Then, just as a collision seemed imminent, Jack pulled up, missing Vordo and his men by inches. Vordo veered out of the way but Jack repeated his maneuver.

The Hardys and Chet momentarily forgot their predicament as they admired Jackâs flying skill. At times he came so close to the surface that little water spouts were generated by the whirling propellers.

âWow!â chortled Chet. âVordoâs getting discouraged.â

âIâd say heâs scared to deathâand who wouldnât be. Attaboy, Jack!â Joe grinned.

Again and again Jack Wayne made close passes at the powerboat, forcing Vordo and his cohorts farther away from the boys. By the time the three sleuths neared the mainland, their pursuers were lost from sight. Jack then flew high above the boys, waggling his wings in salute.

Upon reaching shore, the Hardys turned Burly Wilkes over to the authorities. A police helicopter was immediately dispatched to the islet. Soon a report was radioed in from the copter. The island was deserted, and a search of the surrounding area had revealed no clues to the suspects.

Frank asked an officer if he might make a phone call to Ty Carterâs airfield. Moments later he had Jack Wayne on the wire.

âThanks for getting us out of this one,â Frank said. âThat was great flying.â

The pilot chuckled. âI donât mind a little exercise now and then.â

âDid you notice where Vordo was headed?â

âThey took a northerly course, but I couldnât trail them because my fuel ran low. Sorry. I did give the police the lead.â

Frank asked Jack to meet them at the hotel. âWeâll stay at least another day, in case something turns up. Better bring the car you rented.â

Next morning the Hardys received a telephone call from Ty Carter. He said a helioplane had just landed at his field.

âWhatâs the registration number?â Frank asked excitedly.

When Carter told him, Frank noted that it was identical with that of the helioplane they had chased.

âI donât think itâll be staying here long,â the man continued. âThe pilot is sitting in the cockpit. Apparently he expects some passengers to show up any minute.â

âCan you delay their take-off for a while?â Frank asked.

âI donât know. The guy seems to be in a great hurry. But Iâll try.â

Jack Wayne and the boys drove to the airport immediately and ran to the operations shack.

âTheyâre taxiing out for take-off right now,â Carter told them. He pointed through the window at the helioplane as it moved slowly toward the active runway. âI couldnât delay them any longer. The pilot asked that his plane be refueled. I told my line boys to take their time about it. But the pilotâs passengers arrived.â

âVordo and his gang!â Joe exploded.

âLetâs head them off!â Frank urged.

The boys dashed to their car and drove out after the taxiing aircraft. Moments later the car came to an abrupt halt, bogged down in a stretch of marshy ground just off the airport taxiway.

âOh nuts!â Chet blurted.

âTheyâre getting away!â Joe shouted.

Frank jumped out and chased after the helioplane. His companions followed. He was the first to reach the craft, just as it lined up for take-off. He recognized three of the passengersâVordo, Bleeker, and the steward Timken. Frank lunged at the plane, but stumbled, lost his balance, and fell across the tail. The aircraft was moving so fast he could not let go.

Joe, Chet, and Jack, who had continued the chase, now stopped in their tracks and watched in horror.

The plane continued its take-off run, with Frank clinging desperately to the tail!

CHAPTER XI

Important Assignment

FRANK fought back panic as the helioplane lifted off the runway. With both hands he grabbed hold of one of the elevators and hoisted his body farther onto the tail.

He could feel the pilot tugging at the control wheel, but Frankâs desperate hold on the elevator kept it from moving. The pilot was forced to reduce engine power and drop back down onto the ground.

He jammed the brakes on hard, then executed a partial ground-loop to avoid going off the end of the runway. The movement flung Frank from the tail onto the grass-covered shoulder.

Getting to his feet, dazed but unhurt, he watched helplessly as the plane headed down the runway. In a moment it had left the ground and was soaring upward.

âQuick!â Frank shouted as he ran to meet Jack Wayne and the others. âLetâs follow them!â

âYou okay?â Joe asked.

When Frank said Yes, the four pursuers leaped into the Hardy plane and quickly took off. Ahead, Joe caught a glimpse of reflected sunlight flashing from the helioplaneâs metal wings.

âThere it is!â he yelled.

Jack rammed the throttle ahead as far as it would go. He climbed rapidly above the altitude of the fugitives, then dived to get extra airspeed. The maneuver began to close the distance between the two craft.

âWeâre gaining on it!â Joe observed.

Chet pointed to the right wing of their own plane. âLook!â he yelled. âThe fuel cap is loose!â

âOn the left wing, too!â Joe shouted. By now both caps were vibrating furiously.

âThat canât be,â Jack Wayne insisted. âI checked them myself after I refueled!â

âThis must be Vordoâs doing!â Frank surmised.

The next moment the two caps came loose and fluttered in the wind on the small chains which held them to the tanks. Instantly the slipstream began to drag fuel from the wings. As two gossamer-like columns sailed off into the distance behind them, Jack Wayne applied hard aileron and rudder and turned back to the airport.

âIâm landing!â he said. âWeâre losing every drop of gas. I just hope a spark from the engine exhaust doesnât ignite that trail of fuel, or weâre goners!â

Tensely the boys watched gallon after gallon of high octane spray from the open tanks.

âHow long will she keep running?â Frank asked anxiously.

âI donât know!â Jack replied. âBut by the look of our fuel gaugesânot long!â

Finally the airport came into view. Jack entered the traffic pattern just as their tanks ran dry. Starved of fuel, the engines sputtered, then quit completely. Fortunately, the plane was high enough to glide safely to the field.

âWhew!â Chet murmured as the wheels touched down lightly. âThatâs the closest Iâve ever come to being barbecued.â

Jack grinned. âI was once told that flying involves long hours of boredom, interrupted by moments of extreme fright.â He took a deep breath. âThis was one of those moments.â

âNo use trying to go back up after the helioplane,â Frank said disconsolately.

He telephoned Kenneth Dell at Great Circle Airways and told him of Burly Wilkesâ capture and their fatherâs escape.

âI learned about it yesterday,â Dell replied. âIn fact, your father was in contact with me.â

âWhat!â Frank said excitedly. âYou talked to Dad?â

âYes. I would have told you sooner, but I didnât know where to get in touch.â

âBut he escaped over five days ago,â Frank said. âWhy didnât he let us know? Is he okay?â

âHeâs fine,â Dell assured him. âHowever, I donât know where he is. He wants his whereabouts kept secret. Said heâd explain everything later and asked me to inform your mother, which I did.â

Dell added that he had an important assignment for the boys, and would like to meet them at their home in Bayport the next day.

âThanks,â Frank said. âSee you tomorrow.â

Mrs. Hardy and Aunt Gertrude were overjoyed to see Frank and Joe that evening. But they were worried that Mr. Hardy was keeping his whereabouts a mystery.

âHeâs probably traveling incognito and in disguise,â Aunt Gertrude said.

Thoroughly exhausted by their recent adventures, the boys went to bed shortly after dinner. The next morning they enjoyed a hearty breakfast of wheatcakes and sausages, then adjourned to their fatherâs study. Kenneth Dell arrived shortly and joined the boys in the upstairs room.

âWell, I suppose you want to hear the assignment?â he asked, smiling.

âYes,â the boys replied, and Frank added, âWhatâs your plan for us, Mr. Dell?â

âHow would you like to fly to Scotland?â

The query caught the young detectives by surprise. âScotland?â Joe echoed incredulously.

âThatâs right.â Dell rose from his chair and began to pace the floor slowly.

âTwo days ago I called Scotland Yard. They told me there have been several remarkably clever jewel thefts lately in Scotland. Each of them oc curred on a day when the steward Timken was over there. The Yard checked and learned that he had visited Hextonâs castle on those days.

âSo we were right,â said Frank âHe is one of the gang.â

âYes, but as usual there is no usable evidence.â

âIf only Frank and I could get inside that castle,â said Joe, âwe could get the goods on both the UGLI operation and the robbery ring.â

âThatâs exactly the idea,â said Dell. âMy airline is cooperating with the Scottish police and Inspector Clyde of Scotland Yard. I want you to go over as my operatives.â

âWeâd sure like to take a crack at it!â Frank declared.

âWhat about SKOOL?â Joe asked.

Dell shook his head. âNo sale. Theyâre going straight for Hexton himself and theyâre sure heâs not at the castle just now.â

âHave the authorities over there made any progress on the thefts?â Joe questioned.

âSo far, they havenât turned up any evidence incriminating Hexton. One police official there will be working with youâInspector Clyde. Heâs a member of the London Metropolitan Policeâthatâs Scotland Yard, you know.â

The boys nodded.

âClyde is on special assignment in Scotland to see what he can dig up on our magician friend.â

âWhen do you want us to leave?â Frank asked.

âOne of our planes departs day after tomorrow.â

âWeâll be ready!â Frank promised.

âAnd by the way,â the security chief added, âif youâd like to bring your friend Chetââ

âA herd of elephants couldnât stop him from coming!â Joe put in.

Dell said he would meet the boys at the Great Circle base for a final briefing the day of the flight. He then wished them luck and left.

Brimming with excitement, Joe phoned the news to Chet. âA castle in Scotland!â their chum exclaimed. âWow!â

âMaybe we can find another magic silver bowl for you,â Joe said jokingly. âOne that works.â

âAw, come on,â Chet protested. Then he perked up. âBut wait till you see some of my new tricks!â

âWeâll see them when we get back,â Frank advised him. âRight now weâd better think about packing.â

âYou fellows just donât have any appreciation of my uncanny skill,â Chet said and hung up.

Mrs. Hardyâs and Aunt Gertrudeâs reactions to the coming trip were quite different. âScotland!â the boysâ aunt exclaimed. âFirst your father decides to play hide-and-seek, now you two want to go traipsing into danger on the other side of the Atlantic!â

Mrs. Hardy looked at her sons with a worried smile. âYou know you have my permission. Just promise me youâll be careful.â

âOf course we will,â Frank and Joe assured her.

After supper they began preparations for their trip. Frank had just brought suitcases from the attic when the phone rang. He picked up the receiver.

âAre you Frank Hardy?â a man asked.

âThatâs right.â

âIâve got to see you.â There was a note of urgency in the callerâs voice. âItâs important.â

âFirst, suppose you tell me who you are,â Frank said.

âIâm Stan Mazer, pilot of the helioplane!â was the astounding answer.

CHAPTER XII

A Startling Welcome

AMAZED and perplexed by the call, the Hardys agreed to meet the helioplane pilot the following day at their home.

âWhy should he want to come here?â Joe asked. âIf heâs an UGLI agent, youâd think this is the last place heâd visit.â

âItâs sure strange,â Frank agreed. âI canât wait to hear what he has to say. In any case, I think we should notify Dell to have him followed when he leaves here.â

âRight.â Joe telephoned the SKOOL man.

Late the following morning Stan Mazer arrived at the Hardy home. He was a middle-aged man, of medium height and slender build, and had a troubled expression.

âIâm Mazer,â he announced.

The Hardys led him into the living room and they all sat down.

âYouâre the pilot of Hextonâs helioplane?â Frank asked.

âThatâs right,â Mazer answered. âI was hired about two months ago.â He shifted nervously in his chair. âI needed a job so badly I snapped it up without question. But I didnât know it was connected with anything illegal.â

âWerenât you ever suspicious?â Joe asked.

âYes, from time to time, but I wasnât sure. Actually I closed my mind to the whole situation until you tried to stop my take-off.â

âIt was a pretty unnerving experience,â Frank said dryly.

Mazer apologized. âI didnât know you were clinging to the tail until you were thrown clear,â he explained. âI wanted to get out and help you, but Vordo forced me to take off.â

âWhat about the day we chased you and Timken?â Joe said. âYou turned right into us. We nearly collided!â

âI didnât know that was you,â Mazer said, surprised. âI thought it was some hot-shot pilot wanting to play games. I pulled that maneuver hoping Iâd throw a scare into him. Sorry.â

When Frank asked Mazer where he had taken Vordo and his cohorts, the pilot replied, âTo a large airport near New York City. When we landed, Vordo and his companions deplaned and disappearedâI had no idea where.â

Mazer said that while he was parking the helioplane, he was confronted by a Federal agent, who told him that all FAA offices had been alerted to be on the lookout for the aircraft. To his surprise, the registration papers turned out to have been obtained under a fictitious name and address.

âThe agent immediately impounded the plane,â Mazer said, âand my pilotâs license was revoked pending a hearing.â

The Hardys asked him if he knew anything about their fatherâs being kidnapped.

âI know nothing about that,â he insisted, âalthough I did suspect something strange was going on in the lighthouse.â

âIn what way?â Joe asked.

âI was never allowed to enter,â the pilot answered, âor even to remain long on the islet after delivering my passengers.â

Frank pretended to be suspicious of the story. âAre you going to tell us you donât belong to the same secret criminal organization Hexton does? He wouldnât let you work for him if you didnât.â

âWhat do you mean?â Mazer asked, and his amazement seemed genuine. âI never heard about any criminal organization and Iâm certainly not a member!â

Joe asked him, âHow did you learn who we are, and where to contact us?â

âVordo mentioned your names during my last flight,â Mazer replied. âHe said youâre smart detectives.â

Frank looked at the pilot searchingly. âWhat made you decide to come here and tell us all this?â

Mazer appeared harried. âAfter what happened at the airport, I knew Iâd become involved in something that would get me into deep trouble,â he confessed. âI thought if I told you fellows what I know, youâd help me.â

Frank and Joe sensed that the pilot was being honest, and a slight nod between them said, âHeâs okay.â They promised to do what they could and advised Mazer to repeat his story to Kenneth Dell.

âIâll do it at once,â he said.

When the pilot left, the boys chuckled at the thought of the agent who had been assigned to follow Mazer. âIâd like to see his face when he tails him to Dellâs office,â said Joe.

The Hardys spent the rest of the day packing. Their flight to the Great Circle base was scheduled for the following morning.

Late that afternoon Chetâs bright-yellow jalopy screeched to a halt in front of the Hardy home and the chubby youth leaped out.

âIâm packed and champing at the bit!â he exclaimed as he greeted his friends.

âGood!â Frank said. âHow about dinner? Aunt Gertrudeâs trying out a new recipe for beef stew.â

âWellâokay, but Iâll have to make it fast. I want to get home in time for supper!â

Chet then assumed a nonchalant air. Strolling slowly around the room, he began to whistle softly. The boys watched as he extended his arms in front of him, then clenched his left hand into a fist. From it, with his right hand, he drew out a vivid purple silk scarf, followed by a train of varicolored kerchiefs.

âBravo!â Joe said, clapping loudly.

âGreat trick, eh? I thought youâd like it.â

When the last scarf refused to come out, however, Chet became aggravated. âWhatâs the matter with this thing?â He tugged on it violently.

âSomething go wrong?â Joe needled.

Suddenly the kerchief pulled free and dragged the lining of Chetâs jacket sleeve along with it. A small black container was revealed. From it popped a metal spring which shot through the air, then bounced around the floor like a grasshopper.

âSo thatâs where all those scarfs came from,â Frank said. He tried not to laugh.

Chet whipped off his jacket and frantically stuffed the lining back into the sleeve. As he chased the bouncing spring around the room, the Hardys burst into howls of laughter.

âYou fellows are a jinx when it comes to my magic tricks,â Chet said indignantly.

âMaybe Hexton will give you a few pointers when we get to his castle,â Joe teased.

By the time Mrs. Hardy and Aunt Gertrude announced dinner, Chet had regained his composure. He had a second helping of dessert, then decided he must leave.

âThanks for the delicious meal,â he said.

Chet slowly rose from the dinner table. He stuffed the string of silk kerchiefs into his pocket and lumbered out to his jalopy.

The next day Frank and Joe said good-by to their mother and Aunt Gertrude, then drove off. They picked up Chet and went directly to the Bayport field. Jack Wayne was already warming up the engines when they arrived.

Tossing their luggage into the planeâs baggage compartment, the boys climbed aboard and strapped themselves into their seats. Minutes later they were streaking down the runway on take-off.

Kenneth Dell was waiting for them at Great Circleâs base. He gave a long briefing, then at six P.M. led the boys to the plane that was to whisk them overnight to Scotland. Chet and the Hardys took their seats with the other passengers. Soon the sleek jetliner roared down the runway, lifted off, and headed over the Atlantic.

After a while Chet struck up a conversation with a pretty red-haired stewardess. She managed to keep him amply supplied with food, while he related stories of his long and daring hours in the air.

âI donât like to boast,â Chet said as he munched on a plateful of cookies, âbut Iâm going to wake up some morning and find Iâve sprouted wings if I donât spend more time on the ground.â

Frank and Joe, meanwhile, studied every passenger aboard, occasionally strolling up and down the aisle on the chance they might recognize some member of Hextonâs gang. But nothing seemed to be amiss. Also, no one indicated to the Hardys that he was a SKOOL man.

Suddenly the loudspeaker crackled to life. âThis is your captain speaking,â announced a deep voice. âWe expect to encounter a cold front in a few minutes. The weather forecast lists it as a weak system, so there should be only light to moderate turbulence. We should be through most of it in forty minutes. Please fasten your seat belts and relax.â

The boys looked out the window. Already the blue sky was beginning to be obscured by wisps of gray clouds. It grew so dark that the cabin lights had to be turned on. The jetliner began to toss jerkily. Chet fell quiet as the stewardess returned to her seat. He stared straight ahead with a blank expression.

âWhatâs wrong with you?â Frank called across the aisle.

âIâI feel awful,â Chet moaned. Seeing the stout boyâs expression, the Hardys knew he had overeaten.

Chet remained tight-lipped for nearly fifty minutes until the plane came out of the churning clouds and into clear air. By this time he was asleep.

Several hours later the captain announced that the plane was commencing a gradual descent to Prestwick Airport, Scotland. For a moment the jetliner was enveloped in a milky whiteness as it entered a blanket of stratus clouds that stretched for miles north of the Irish Sea.

Frank looked down while the plane descended through the overcast. âThat chain of islands over there must be the Hebrides,â he said.

âAnd look!â Joe added, pointing off in the distance. âThereâs Ireland.â

Suddenly Chet snapped alert. âWh-where are we?â he asked.

âJust coming up on the Scottish coast,â Joe told him. âHow do you feel?â

Chet rubbed his eyes. âOhâokay, I guess,â he answered sleepily. âBut never again so much food!â

âOh no?â Joe grinned.

At seven oâclock Greenwich time, the jetlinerâs wheels touched down on the macadam surface of the runway and taxied to the parking ramp.

As the boys walked across the ramp toward the administration building, a shiny black car marked âPoliceâ sped up to them. Seated behind the wheel was a man with a large sweeping mustache and a hat pulled low over his eyes. He rolled down the window and called out, âAre you the Hardys?â

âThatâs right,â Frank answered. âAnd our friend Chet Morton.â

âInspector Clyde sent me to fetch you chaps. He wants to see you right off. Weâll send for your luggage later.â

âWhat about customs?â Frank inquired. âWeâve already arranged special clearance,â the driver explained.

Frank, Joe, and Chet squeezed into the back seat. On the floor in front a blanket covered a large package. The car started off with a violent lurch. It sped across the airport ramp, out through an exit, and onto a road leading away from the field.

At that moment the driver yanked off the blanket. A man crouched beneath it straightened up and settled in his seat. The boys were flabbergasted at his sudden appearance.

âWh-whatâ?â Frank started to say, when the man turned around and faced them. They gasped.

Vordo!

CHAPTER XIII

Sky Spies

As the boys stared in dismay, the driver pulled off his false mustache and removed his hat. Stony Bleeker!

Vordo looked at the Hardys with contempt. âInsist on poking your noses into our business, hey?â he growled. âWeâll fix you for good!â

Frank realized that the boys could not risk attacking their abductors. The driver would surely lose control of the car and all might be killed. Besides, the men undoubtedly were armed.

Frantically the Hardys searched for a way out of their dilemma. Frank noticed that Bleeker was beginning to drift to the right.

Vordo also saw what was happening. âGet over to the left!â he snapped. âYou know they drive on the opposite side of the road here!â

Bleeker swerved the car sharply to correct his mistake. âSorry,â he said, mopping his forehead. âI keep forgetting weâre not in the U.S.â

âSee that you donât forget again,â Vordo growled, âor the Hardys and their fat friend wonât be the only ones to regret this ride!â

Farther along, the road bent sharply in a hairpin curve. As Bleeker rounded it, he again instinctively favored the right side.

âGet over, you idiot!â Vordo bellowed, seeing a double-decker bus coming head-on.

Bleeker spun the wheel and the car rocked violently. Then, with a splintering crash, it tumbled over on its side! Vordo and Bleeker were thrown clear.

The three boys scrambled dazedly from the vehicle. The bus had stopped a short distance down the road. Its driver and several passengers were running toward them.

âAre you lads all right?â shouted the driver.

âYes!â Frank called out. He then ran around to the front of the car. âOur men! Where are they?â

One of the passengers pointed off into the distance. âI saw two men disappear over that dune as we ran from the bus.â

The boys gave chase but found no sign of Hextonâs henchmen.

âWeâve let Vordo and Bleeker slip through our fingers again!â Joe said in disgust.

âBut weâre free,â Frank reminded him.

âAnd still in one piece,â Chet observed.

He and the Hardys walked back to the bus. Frank asked the driver to notify the police. Before long, three constables arrived to take the boysâ story and examine the car. They said it was a stock model, rigged up to look like a police car.

âClever job,â a constable remarked. âI can see how it fooled the airport police.â

He drove the boys back to Prestwick, where they checked through customs. One of the officials, recognizing their names on the passenger manifest, said that an Inspector Clyde had telephoned him shortly before they had landed.

âYouâre to meet him at the chief constableâs office in Ianburgh,â he said. âA car has been sent to pick you up.â

The boys thanked him and lugged their suitcases to the front of the terminal, where the car was waiting. This time the driver produced a card to identify himself and the boys got in.

The trip to Ianburgh took little more than an hour. The visitors were intrigued by the pleasant rolling countryside, dotted with stone and thatch-roofed cottages.

At the chief constableâs office they were greeted by a tall, distinguished-looking man who introduced himself as Inspector Clyde of Scotland Yard.

âMy dear chaps,â he said crisply, âI am sorry you have had such a rough reception.â He turned to a stocky man with bristly gray hair and mustache. âThis is my colleague, Chief Constable Burns.â

âIâve had a report on your kidnapping, of course,â said the constable as he shook hands. âIt was a daring trick. I think this gang has the wind up.â

âTheyâre scared,â Frank agreed. âAnd that makes them more dangerous. But it doesnât matter. Through Hexton we might be able to identify the other members of UGLI and break the whole organization. But first we must get the goods on Hexton.â

âThat we must,â Clyde said grimly. âUGLI has secret eyes and ears in every country of the world.â

Burns nodded. âThe jewel robberies are big-and very cleverly doneâbut they are nothing compared to the international danger.â

âWill you be in charge of the investigation in Scotland?â Frank asked the inspector.

âNot officially,â Clyde replied. âI have been invited to cooperate with the Scottish authorities.â

The chief constable smiled at the boys. âScotland Yard is tops, you know. Local authorities are often pleased to have them lend a hand.â

âThereâs something that has always puzzled me,â Chet interrupted. âHow come Scotland Yard isnât in Scotland?â

âMany years agoâin 1829 to be exact,â the inspector explained, âa police station and office were set up in a private house at Number 4 Whitehall Place in London. The rear of the house opened onto a court named Scotland Yard because it was part of the palace grounds where the kings and queens of Scotland lodged when they visited the English Court in medieval times.â

Frank was eager to return to the case. âInspector Clyde,â he said, âJoe and Chet and I would like to try to get into Hextonâs castle.â

âGood boys,â said Clyde. âDell told me you suggested it.â

âWhere is the place?â Joe asked.

Chief Constable Burns unfolded a map on his desk and the boys leaned over to study it. âAbout one hundred miles north of Ianburgh.â He put his blunt finger down on a spot. âThere it is. A huge stone fortress, set deep within a private park surrounded by miles of high iron fence.â

Joe grinned. âSounds like fun, getting in.â

âActually,â said Clyde, âsince the gang have impersonated officers and attempted kidnapping, we have a right to go there and demand entrance. But it would be defeating our purpose.â

Frank nodded. âYes. Vordo and Bleeker have sounded the alarm by now. Besides, by the time you got through the gates and up to the castle, every bit of evidence would be well hidden.â

âItâll have to be an undercover job,â Joe agreed.

âMaybe we could start by spying on it from the air,â Frank suggested.

âCapital idea!â the inspector said.

âI know exactly the man who can help you,â said Burns. âAaron McHugh. Heâs an excellent pilot.â

The chief constable said McHugh flew in the vicinity of Hextonâs castle on a charter to the Hebrides, so the sight of his plane in the area would not be likely to arouse the suspicion of the magician and his men.

After leaving the constableâs office, the boys went to their hotel and registered, then had showers, food, and several hours of rest.

That afternoon they were introduced to Aaron McHugh, a middle-aged man with a jutting square jaw and a crop of wiry brown hair that sprang out from his head.

The pilot was unusual looking, but his plane, which he used to haul cargo, was even more so. The boys were surprised and amused to see a metal-covered, trimotored craft with unusually thick wings and a system of exposed control cables that stretched back to the tail. Although the craft appeared antiquated, McHugh assured them that it was as durable and reliable as the day it was built.

âMy tin bird is noâ verâ fast, lads,â he explained, âbut itâs a splendid workhorse.â

Frank decided that they should waste no time in getting their first look at Hextonâs castle.

âChet, Joe,â he said, âgot your binoculars and cameras?â

âRighto,â Chet replied.

Joe grinned and slapped the leather case slung over his shoulder. It also contained the Hardysâ high-power photographic equipment.

The trio climbed aboard the plane and sat down on the floor. McHugh fired up the three engines. The craft lumbered along during the initial take-off run, then began to bounce lightly across the rough turf runway.

Soon it lifted off the ground and started to climb slowly, like a tired bird. When McHugh felt he had sufficient altitude, he tapped the various instruments on the panel with his finger to make sure none of the dials were sticking and giving false indications.

âWe have a wee bit of a headwind,â he announced, âso it will take about an hour to reach our destination.â

The boys enjoyed the flight as they gazed down at the craggy landscape of the Scottish coast. As McHugh had estimated, nearly an hour elapsed before he pointed ahead.

âThere it is!â

He adjusted his course, then rolled the plane into a shallow bank to give the boys a better look. Far below was the large stone castle. Its sturdy gray battlements were sharply defined from an altitude of three thousand feet.

âIt must be centuries old,â Joe observed.

âAbout the eleventh century,â McHugh said.

Chet exclaimed, âIt has a moat, too, just like in the history books, but thereâs no water!â

âNowadays, with planes,â said their pilot, âa moat of water isnât much protection.â

Frank asked McHugh to circle the castle without getting too close. Using binoculars, they peered down. Frank observed that the castle was on high ground, without trees or shrubbery, and noted that it would be impossible to approach it on foot without being seen.

Joe extracted a camera, attached a telephoto lens, and clicked off one frame after another. Presently his viewer picked up two men on the castle wall.

âOh-oh!â he exclaimed. âWeâd better get out of here. I think weâve been spotted.â

McHugh turned the plane back toward Ianburgh. When the craft landed, the Hardys hurried to the police darkroom to develop their photographs. To their disappointment, the glare of the sun on the planeâs window had obscured a clear view of the castle.

âRotten luck!â Joe exclaimed.

âWeâll take another crack at it,â Frank said.

He suggested that in order to avoid arousing suspicion, this should be done during one of McHughâs regular charter flights.

âTomorrow morning Iâm taking a load of feed to the sheep raisers near Stornaway in the Hebrides,â the pilot told them. âCome along.â

Shortly after dawn, McHugh and the boys again boarded the plane. Its fuselage was crammed with feed bags, and the three passengers had to worm their way to separate spots near the windows. The pilot started the engines and taxied out for take-off.

Without warning, a man appeared from behind a stack of feed bags and darted for the passenger door. Frank grabbed him and uttered a cry of surprise when he recognized the intruderâs face. Timken, the Great Circleâs steward! UGLI spying again!

âLet me out!â Timken shouted frantically. âI want to get off! You hear me?â

âIâm not deaf,â Frank said, pinioning the man against one of the sacks. âWhy are you here?â

As he spoke, the plane lifted. âWeâre already airborne,â Frank continued. âI wouldnât suggest your taking a walk just now!â

With a snarl, Timken thrust his feet against the cabin wall and broke Frankâs grip. He grabbed a feed bag and threw it at the boy, knocking him to the floor. But Frank sprang up and leaped at his attacker. Timken threw a punch, which Frank ducked. He got off a hard counterblow, catching the man squarely on the chin. The steward fell, unconscious.

âJoe, Chet!â Frank called out over the roar of the engine. âLookee here! We have company!â

The boys climbed over the sacks.

âTimken!â Joe cried as he gazed in amazement at the man on the floor.

âRight.â

âWhatâs he doing here?â Chet asked.

âI donât know,â Frank answered. âBut weâll sure find out when he comes to!â

They tied up their unexpected passenger, then tried to revive him. Several minutes elapsed before Timken regained consciousness. When he realized he was still in the plane, he became panic-stricken. âHow long have we been in the air?â he screamed.

âWhy do you want to know?â Frank retorted.

âQuick! Tell me!â The stewardâs face turned pale with fear.

Frank glanced at his watch. âTen ... maybe fifteen minutes.â

âLet me out of here!â Timken screeched. âYouâve got to land this plane, or weâll all be killed! Thereâs a bomb aboard!â

CHAPTER XIV

Nerves of Steel

âA BOMB!â Frank shouted frantically.

âThatâs right!â the steward cried.

âWhere is it?â Frank demanded, shaking Timken violently.

âIn the nacelle of the left engine! You canât reach it!â

Frank dashed to the pilotâs compartment to tell McHugh, who looked out his window at the stretch of rocky coastline below. âI noâ can land in this area, lad!â he said grimly.

âBut we have only minutes!â Frank looked out at the cowled engine, located beneath the left wing. âThereâs just one thing to do!â

âWhatâs that?â the pilot asked.

âClimb out on the strut and try to reach that engine nacelle. Iâll do it.â

âBut I noâ have any parachutes aboard,â McHugh told him. âThe slipstream might pull ye off the strut!â

âI must take that chance,â Frank declared, âor weâre goners!â

He went back to Timken. Seizing the steward by his collar, Frank pulled him to his feet. âExactly where in the engine nacelle did you place the bomb?â he demanded.

âI ... I put it just inside the access door to the oil-filler cap!â Timken stammered. âBut itâs too late! Thereâs nothing you can do!â

Frank grabbed a screwdriver from the pilotâs tool kit and slipped it in a pocket. He asked Joe and Chet to help him kick out the window located directly above the strut leading to the left engine.

As the boys kicked with all their might, the window cracked in several places, then shattered and disappeared below. The thunderous roar of the slipstream echoed through the interior of the fuselage.

Frank squeezed his body out the window. Hooking his legs around the strut, he pushed himself away. The force of the slipstream felt like the hand of some vengeful giant trying to hurl him off into space.

Frank, crouching low, locked his arms about the strut. He then proceeded to shimmy, at a painfully slow rate, toward the engine nacelle. Drawing closer, he moved into the area of the propeller blast and the engine exhausts. The sound was deafening, and the fumes and heat stifled him. However, they made him insensitive to the fact that he was hanging thousands of feet above the ground. Once Frank almost lost his grip.

McHugh reduced power on the right engine in an effort to ease Frankâs ordeal. Joe and Chet watched anxiously, their nerves stretched almost to the breaking point.

Frank tightened his grip on the strut with one hand. With the other he took out the screwdriver and reached for the Dzus fasteners which secured the small aluminum access door on the nacelle.

The wind lashed against his outstretched arm, but he continued to probe for the fasteners. Finally the door loosened. It popped open and flapped violently.

Frank reached in through the opening and desperately felt for the bomb. Nothing! He stretched his arm in farther, his efforts becoming more frantic as his strength began to ebb. Then his hand felt something cylindrical in shape and about the size of a flashlight. Frank locked his fingers around the object and slowly drew it out. There was a small timing device at one end, revealing that the bomb had only seconds to run!

Now to get rid of it!

Looking down, Frank saw that they were still flying over a desolate stretch of coast. He flung the bomb from him and watched it hurtle down and behind the plane. It was almost out of sight when a white-and-black puff of smoke appeared. Seconds later the faint, thudding sound of an explosion could be heard.

Frank slowly worked his way back to the window and with the help of Joe and Chet dragged himself inside. Exhausted, he slumped to the floor.

âWhew!â Joe exclaimed. âThat was close!â

âYou can say that again,â Frank said shakily. âAnother ten or twenty seconds and it would have taken searchers a year to pick up the pieces.â

âThat was a brave deed, lad!â McHugh shouted from the cockpit. âAnd Iâm grateful to ye for saving my ship! Do you want to go back to Ianburgh with your prisoner?â

âNo,â Frank replied. âLetâs continue with the flight as planned. Timken isnât going to give us any trouble.â

The boys returned to Timken. Joe asked, âWho put you up to this?â

âI didnât want to plant the bomb in your plane,â Timken muttered, âbut Vordo ...âThe UGLI assistant stopped short. Obviously their prisoner was fearful of what might happen to him if he talked.

âAnd Vordo got his instructions from Hexton, didnât he?â Frank pressed.

Beads of perspiration oozed from the stewardâs

The pilot reduced power to ease Frankâs ordeal forehead. âI donât know! Vordo threatened me. I had to do it!â

âWhen did you and the others arrive in Scotland?â Joe questioned.

âThe day after you tried to stop our take-off in the helioplane,â Timken answered. âWhile we were at an airport near New York City, the plane was impounded by a Federal agent. When I told Vordo and Bleeker, they decided to get out of the country right away.â

The stewardâs answer confirmed what Mazer, the pilot of the helioplane, had told the Hardys.

âBesides the pilot, there were four men that day,â Joe said. âWho was the fourth?â

âOne of Hextonâs cronies. A guy named Arnold.â

âIs he a spy for UGLI?â Frank snapped.

Timken jumped. âYou know aboutââ The steward caught himself. âI wonât talk to you lunks. Iâve said too much already!â

Joe spoke up. âDonât get so nasty, Timken. You forget that my brother saved your life. What kind of gratitude is this?â

Still no reply.

âListen, buddy,â Joe continued, âyou know youâre going to prison for trying to kill the rest of us. You might get a lighter sentence if you answer a few questions. For instance, what was your racket on the Great Circle flights?â

âI wonât squeal!â Timken shouted, and clamped his lips together.

Joe shrugged. âHave it your way.â The boys left their prisoner.

The plane landed at Stornaway and was quickly unloaded. After a conference, McHugh and the boys decided to return the UGLI agent to Ianburgh. On the return trip the pilot adjusted his course so the boys could take more aerial shots of Hextonâs castle.

Back in Ianburgh, the Hardys handed their prisoner over to the chief constable, who was thunderstruck at the bomb story. He then let them develop their latest photographs. Frank spread the prints out on a table and they all scrutinized them closely. But the pictures revealed no clues.

âThe ground around the castle is as clean as a whistle,â Joe observed. âWe couldnât possibly sneak up on the place without being seen.â

âWhat about climbing up the surrounding wall?â Chet suggested. âRobin Hood used to do it all the time.â

âNot a bad idea.â Joe grinned. âBut it brings us back to the original problem. How do we get inside the fence and up to the wall without being seen?â

Frankâs brow creased in contemplation. âIâm afraid this is a tough one.â He signed. âWhatever plan we come up with will have to be pretty far out.â

At that moment Inspector Clyde arrived. He carried a long, slim black umbrella, which he hooked to the coat rack when he entered the room.

âAh, there you are,â the inspector said. âI have some interesting news for you chaps. Mr. Dell telephoned from the States while you were gone. Heâs leaving for Scotland immediately. Something very important and highly secret has come up!â

CHAPTER XV

A Furious Scot

DELL arrived in Ianburgh that same night and met the boys at the chief constableâs office. There Inspector Clyde ushered them into the interrogation room and the young sleuths told about the capture of Timken.

âGreat work!â the security chief exclaimed. âIâll want to question him myself before I go back to the States.â

When Clyde left the room, Frank said, âI understand something important has come up on your end, too.â

âYes,â Dell replied. âOur investigation has turned up a very interesting lead. Timken has been spending a lot of time with another Great Circle steward named Ross. We checked him out thoroughly and learned that he had a record for petty theft under another name. We suspect heâs part of the Hexton-UGLI setup, but that he and Timken were working together.â

âYou mean they were double-crossing Hexton?â Joe asked.

âYes. I doubt if Hexton would dispose of stolen goods in the clumsy way Timken has been doing.â

âI see,â said Frank. âThese two manage to hold out a diamond here and there from the gangâs robberies, then sell them.â

âRight. We could pick Ross up on suspicion, of course. But Iâd rather give him a little rope. Maybe weâll get a stronger case on him. Catching him first might make it easier to get Hexton.â

âWhere do we fit in?â Chet spoke up a bit fearfully.

Dell smiled. âYour assignment is to make a trip to the United States on our Flight 101. Ross will be steward. Use assumed names and occupations on the plane. Watch Ross and see if you can pick up any leads for SKOOL.â

Joe grinned. âIâll feel like a secret agent on Flight 101!â

When Clyde returned, the Hardys told Dell about their aerial reconnaissance of Hextonâs castle and of their efforts to think of some way to get inside.

The security chief laughed. âSounds tough! But Iâm betting on you.â Dell told them that the next Flight 101 trip from Prestwick to New York was scheduled to depart in forty-eight hours.

âWeâll have time to make another flight to the castle before we leave,â Frank said. âI wonder if McHughââ

Just then the telephone rang and the inspector picked up the receiver. âHello. Inspector Clyde here! ... Oh, itâs you McHugh.... What? ... Good heavens! Thatâs incredible, I must say. Yes! The boys and I will start for the airport straight off!â

âWhat is it?â Frank asked.

âSomebody has cut the external control cables on McHughâs plane,â he answered. âHe wants to see us right away.â

While Dell stayed behind, the inspector and the boys leaped into a police car and drove to the field. McHugh, in a furious mood, stood glowering beside his plane.

âCan you noâ find the brigand who did this?â he shouted. âIâd like to get my hands on him! Here! Look at these!â

The boys examined the severed control cables, which dangled loosely from their connections at the tail and at the point where they entered the cockpit.

âGee,â Chet remarked, âtheyâre cut clean in half.â

âWhen did this happen?â Frank asked.

âIt couldnât have been more than twenty minutes ago,â McHugh replied. âWhile I was at the plane, I was told there was a telephone call for me in the office, so I went there. But no one was on the other end of the line. When I came back here, I found the cables cut!â

âObviously the call was a trick to lure you away from your plane,â Frank observed.

Just then there were sounds of a loud commotion in the airport office. McHugh hurried toward the building, followed by the others.

When they entered, an aircraft mechanic was clutching a stocky man by the arm. Another man, who McHugh said was the airport manager, was questioning the stranger.

âWhatâs going on here?â Inspector Clyde demanded. âIâm with the chief constableâs office!â

âI found this fellow going through my clothes locker,â the mechanic said. âAnd look at what he was carrying!â He held up an oversized pair of scissors.

âThose are metal cutters,â McHugh stormed. âSo this is the brigand who cut my cables!â

âI didnât cut anything!â the man growled.

âLet me at him!â McHugh bellowed, and started to roll up his shirt sleeves.

âCalm yourself!â the inspector ordered. He turned to the man. âWhat were you doing at the locker?â

âIt was open. I thought Iâd look around. Thatâs all!â

âWhat about these cutters?â

âI found âem! Besides, is there any law against carrying metal cutters?â

The boys gazed at the man. There was something familiar about him, Frank thought, but he could not recall where he had seen him before.

Inspector Clyde demanded that the stranger show him some identification. The man hesitated. Then he pulled a wallet from his pocket and handed it to the inspector. It contained an international driverâs license in the name of Karl Arnold.

âArnold!â Frank exchanged a quick glance with Joe. âThe man Timken said was the fourth passenger in the helioplane the day I tried to stop its take-off!â he said to himself. Aloud he exclaimed, âYouâre one of Hextonâs men!â

âHexton? Never heard of him,â the man insisted.

âDonât lie to us!â Joe snapped. âWe know who you are!â

âYouâve got me mixed up with somebody else,â Arnold retorted with a smirk.

âLet me shake it out of him!â McHugh bellowed.

The boys urged the pilot to relax. Then they suggested that Arnold be taken back to the chief constableâs office to have Timken identify him. The inspector agreed to do this.

Arnold seemed unconcerned as they returned to Ianburgh. When they reached the office, they found Dell questioning Timken in the interrogation room. The steward was visibly startled when he saw Arnold.

âWe ran across one of your friends at the airport,â Frank announced.

Timken was obviously nervous. âFriend?â he said shakily. âWhat friend?â

âThis man right here,â Frank replied sharply, pointing to Arnold.

âWhyâIâI never saw him before,â the steward insisted. âI donât know him.â

âStop playing games!â Joe ordered angrily. âThis man is Karl Arnold. You told us about him!â

Arnoldâs face flushed with anger, but he said nothing.

âThat was somebody else,â Timken said. âIâve never seen this man before.â

âSatisfied?â Arnold said indignantly. âNow, if thatâs all, Iâll leave!â He turned and stormed out of the room.

âBut we canât let him go!â Joe protested.

âIâm afraid we must.â The inspector sighed. âWe havenât any evidence to hold him on, but weâll keep track of him.â

âThe inspectorâs right,â Frank assured his brother. âWe have no witnesses who saw him cut the control cables. And there is no law against rrying wire cutters. If heâd resisted the temptation to ransack the employeesâ lockers, heâd have got away altogether.â

Dell looked discouraged as he and the boys left the interrogation room. âI didnât have much luck, either,â he remarked. âTimken wouldnât tell me anything more than he told you.â

âI suppose itâs a pledge the UGLI men take,â Frank said. âBesides, Timken is afraid of Hexton. Thatâs why he wouldnât identify Arnold.â

Minutes later, McHugh stalked into the chief constableâs office. âI hope you have that Arnold fellow in jail!â he declared.

âWe had to let him go,â Frank admitted.

âWhat!â the pilot exclaimed. âWhy, heâs as guilty as a witch!â

âYou donât have to tell us,â Joe murmured.

âCan you repair the control cables?â Frank inquired.

âNo,â McHugh replied. âA new set will have to be made up special. Itâll take two or three days before my tin bird will be flying again.â

âWell,â Frank said, âthat washes out our plan for another reconnaissance flight before our trip. Weâll have to wait until we get back.â

The next day Dell, wishing the boys luck, returned to New York. The following morning the Hardys and Chet were on their way to Prestwick Airport, enthusiastic about their new assignment and the opportunity to spend a couple of days at home before returning to Scotland. Soon they were winging their way westbound across the Atlantic on Flight 101.

Frank was using the name Bud Richmond and introduced himself to a few passengers as an announcer on station WHOX, meaning to him HOAX.

Joe had chosen to be Larry Walker, a student returning from a hike through Scotland. Throughout the flight, both Hardys kept an eye on the steward Ross. Chet, as a pro-football player named Chuck Brown, spent most of his time in the galley getting lemonade and asking Ross a hundred unimportant questions.

He was always being interrupted by a whiskered old man wearing dark glasses, who was seated near the galley. From time to time both the steward and stewardess had to assure him that the wings were not bending off, that the engines were not about to catch fire, and they were sorry that the tea they had served was weak.

The only incident out of the ordinary occurred after landing at Great Circleâs base. The elderly man accidentally tripped Ross with his cane while disembarking from the plane. The steward fell flat in the doorway and the old man leaned down to help him up.

âSo sorry,â he said in a high, quavering voice. The boys had arranged to have Jack Wayne meet them, and after clearing customs, were soon on their way to Bayport. They were sorry not to have picked up any clues for SKOOL, but assumed Ross would be shadowed by agents.

The Hardys dropped Chet off at his farm, then drove quickly to their home. âHello!â Mrs. Hardy cried out, and hugged her sons. âDid you see your dad?â

âNo, Mother.â

âHe phoned a few minutes ago but didnât say where heâs going. Heâs all right, though.â

âWhere did he phone from?â Joe asked.

âI donât know.â

âYou two boys look peaked,â Aunt Gertrude spoke up, âbut a few home-cooked meals will remedy that.â

âItâs good to be back,â Frank declared.

The two women showed their disappointment when they heard that Frank and Joe would be returning to Scotland so soon.

âBut weâre sure eager for a shower and some American chow!â Joe said, grabbing the boysâ two suitcases and bounding up the stairs. He set his bag on the bed and opened it to get a clean shirt.

âHey! Whatâs this?â he exclaimed, and picked up a carelessly hand-printed note from the top of his shirts. It read:

YOUR FATHER WARNS BE CAREFUL. GAME IS VERY DANGEROUS.

CHAPTER XVI

Secret Compartment

âBut who could have written this note and put it in your bag?â Frank exclaimed. âDidnât you lock it?â

âNo, I never do.â Joe looked at the message. âMaybe Hexton found out about our assignment, and had one of his UGLI men plant the note to throw us off the track.â

Joe nodded. âAnd I bet I know when. At Prestwick the porter put our bags on his cart with a lot of other luggage, but then he went away for a while and the cart stood unattended.â

Frank shrugged. âBut what could Hexton possibly hope to gain? He knew it wouldnât stop us and weâre aware itâs dangerous.â

Two days later Frank and Joe were again saying good-by to their mother and aunt. They picked up Chet at the Morton farm and headed for the airport, where Jack was waiting to fly them to the Great Circle base.

On the return trip to Scotland, the plane encountered moderate turbulence, but all the passengers took it calmly. The steward proved to be Ross. When he saw them, the man at once became ill at ease.

After the boys took their seats, Joe whispered to Frank, âI wonder if he suspects weâre watching him.â

During the first half of the flight a blond-haired man, wearing dark glasses, sideburns, a small mustache and a beard, made his way down the aisle several times.

âI have a feeling heâs looking us over,â Frank said. âWeâd better watch him as well as Ross.â

Nothing suspicious happened during the flight, however, and in the morning the jetliner landed at Prestwick Airport. Frank and Joe made a point of being the last passengers to leave. Chet was just ahead.

While debarking, they all noticed that the steward seemed in a hurry to leave the plane. He ran down the steps after them and shot past. Instantly the man in the dark glasses hurried toward the steward. Ross, seeing him, broke into a run. The passenger sprinted ahead.

âCome on!â Frank exclaimed. âLetâs see whatâs up! It could be that passenger is a SKOOL man! Maybe we can help him!â

The boys dashed after the two men, who disappeared around the corner of a hangar. Frank spotted the steward running into the building.

âChet! Stay outside and cover the exits!â Frank cried. âJoe and I will go in after him!â

The building was filled with aircraft, which made it difficult for the Hardys to spot their quarry.

âLetâs split up,â Frank suggested. âIâll cover the left side, you take the right.â

The boys separated. As Frank slowly wound his way among the aircraft, he heard a muffled noise and stopped to listen.

Bummf.

There it was again! The young sleuthâs attention focused on a twin-engine plane directly ahead. Cautiously he stalked toward the cabin door. Just as Frank reached it, the door burst open and slammed into the boyâs head with a force that made him cry out and sent him crashing to the floor. Half dazed, Frank looked up to see Ross leap from the craft and dart toward a side exit of the hangar.

âWhatâs going on?â Joe called as he ran past the closely packed planes to his brotherâs side. âAre you all right?â

âIâm okay,â Frank replied, getting slowly to his feet. âJust a little dizzy. Quick! Outside! Maybe Chet spotted Ross leaving the hangar!â

As the Hardys dashed from the building, they saw Chet leaning against a low wire fence which enclosed an automobile parking lot. He was breathing hard.

âG-golly, but that guy could run!â the stout youth gasped as the Hardys approached him. He gulped in more air. âHeâs faster than a gazelle.â

âYou mean the steward?â Joe asked.

âYes.â

âWhere did he go?â Frank queried.

âHe jumped the fence into the parking lot and roared off in one of those little foreign sports cars,â Chet answered. He stared at the ground with a sheepish expression, then began to shuffle some pebbles with his foot. âSorry I goofed, fellows. I was checking the rear of the hangar when Ross zipped from the side exit. He had too much of a head start.â

âThatâs okay,â Frank said. âIt would take a dozen men to cover a building that size.â

âHey! And something else!â Chet exclaimed, glancing up. âJust after you two chased inside after the steward, I caught a glimpse of that guy in the dark glasses watching from around a corner of the next hangar.â

âDid you let on that you saw him?â Frank asked.

âYes,â his chum admitted. âIn fact, I started walking toward him and he ducked behind the hangar. I thought of chasing him, but I didnât want to leave the exits unguarded.â

âItâs funny,â said Frank. âHe was chasing the steward, but apparently didnât try to catch him.â

âThatâs not the only mystery,â Joe added. âChet, we wonder if that passenger is a secret agent from SKOOL. Letâs try to find him and give a sign weâre sort of working second hand for the organization.â

âWhat kind of sign?â Chet asked.

âOh, we could talk about school and school rings,â Frank answered.

Chet was enthusiastic at once. âIâd feel a lot safer if I could hook up with a full-fledged SKOOL man.â

The three boys made a thorougn search of the place but failed to find the man. At last they gave up, went through customs, and took a taxi to Ianburgh. When they arrived, they found Inspector Clyde and the chief constable anxiously awaiting them.

âOne of the constables was rechecking Timkenâs personal effects and he discovered a secret compartment in his wallet,â the inspector explained. âLook what he found thereâmost extraordinary.â

He handed an envelope to the young sleuths. Inside were a one-way train ticket to Edinburgh and a newspaper clipping. The item was headed:

Nairn Loch Manor to Be Opened to Public

Newly Discovered Jewel Collection on Display

âNairn Loch Manor? Jewel collection? Whatâs this about?â Joe asked.

âThe Manor is to be maintained by the Scottish Trust as a historical shrine,â Burns explained. âWhen they began to renovate it a few months ago, a worker discovered a magnificent collection of jewels hidden beneath the floor. It is said they were placed there about four hundred years ago.â

âI remember reading about the discovery in a newspaper back home,â Frank recalled. âThe value of the collection is considered second only to the crown jewels in the Tower of London.â

âPrecisely,â the inspector replied.

Joe looked at the clipping and train ticket again. âDo you think Hexton and his UGLI men might be planning to steal the collection?â

âI donât know,â Inspector Clyde admitted. âWe have to consider that possibility, of course. But the place will be so heavily guarded that any thieves will be caught.â

âWhy would Timken go to Edinburgh by train?â Joe asked. âI should think the thieves would use a car for a quick getaway.â

âMost likely they will,â Frank said. âMaybe Timken was only being sent there to case the place for Hexton.â

âExactly the conclusion I came to,â Inspector Clyde declared. âNow theyâll have to use someone else.â

Joe snapped his fingers. âPerhaps thatâs where Ross was heading.â

âWeâll check,â Clyde told him.

Frank was thoughtful for several seconds, then said, âProbably Hexton, with his sleight-of-hand ability, will do the actual stealing.â

The conversation turned to the reason the boys had come to Scotlandâto get into Hextonâs castle.

Inspector Clyde paced the floor in thought. âThe question remains, just how do you manage to do that?â

âPerhaps another reconnaissance flight will give us an idea,â Frank suggested. âLetâs alert McHugh.â

âOh!â Burns said quickly. âHe isnât available at the moment. Heâs off ballooning.â

âHeâs what?â Joe asked, with a puzzled expression.

âBallooning,â the chief constable repeated. âMcHugh belongs to a club of enthusiasts who go darting about in bags filled with hot air. Jolly good fun, they think, unless they get caught in a tree, or on a church spire. Theyâre having a race somewhere near Perth.â

âWhat a ball!â Chet burst out. âIâd like to see that.â

âHold on!â Frank put in. âThat solves our problem. Weâll balloon into Hextonâs castle!â

CHAPTER XVII

Night Attack

INSPECTOR Clyde laughed. âSee here, my dear fellow. Youâre not serious about ballooning into Hextonâs stronghold, are you?â

âI realize it sounds fantastic,â Frank admitted. âBut at least itâs worth discussing with McHugh.â

Joe scratched his head dubiously. âHextonâs guards are bound to spot a balloon.â

âMaybe not if we drop in at night,â Frank replied.

Chet pointed a determined finger at his friends. âDonât think you two are going to get me to ride in one of those oversized basketballs!â

Joe grinned. âOkay. Anyway, I donât believe thereâs enough hot air in Scotland to lift you off the ground!â

A little later the boys rented a car and drove to the site of the race. On a grassy plain a few miles west of Perth, more than fifty balloons of all shapes and sizes were preparing for the competitions. Their bright colors and vivid designs gave the scene a touch of the pageantry of a medieval tournament.

âLook at that!â Chet yelled as they walked across the field. He pointed to a balloon displaying the French national colors from its gondola. âWhat a beauty!â

At the firing of the starting gun, the contestants leaped onto bicycles, sped to their balloons, and jumped into the gondolas. Then the balloons were released from their moorings and sailed across the field. One of them never lifted off the ground; another, the French entry, rose into the air but became snagged in a tree branch.

âNom dâune pipe!â screamed the flier. âIl est fichu, mon beau ballon!â

âTough break,â said Joe.

Frank asked one of the club members for McHugh. He learned that the pilot was not racing that day, but was helping another contestant a short distance down the field.

McHugh was surprised to see the boys. Frank told him about the plan for getting into Hextonâs castle.

McHugh chuckled. âSo ye want to be invaders?â he teased. â âTis a daring plan yeâve come up with, lad. And it will noâ be an easy thing to do.â

âCan you get a balloon large enough to carry all of us?â Frank asked.

âSure. Weâll borrow one from the club.â

âIâm not going,â Chet insisted.

âBut we need you for ballast,â Joe said with a grin.

âIf we get into Hextonâs castle,â Frank added, âyou might see some of his magic equipment!â

âWellââ Chet muttered, weakening. âI guess youâll need somebody around to keep you two out of trouble.â

After the races, McHugh and the boys returned to McHughâs apartment in Ianburgh to plan their daring adventure. The pilot examined an aeronautical chart and carefully plotted the position of the castle. He pointed out that their success depended entirely upon the winds and the position from which the balloon was launched.

âI understand a balloon has no directional control,â Joe said.

âThatâs not entirely true,â McHugh replied. âSince the wind direction generally changes with altitude, we can get some control by ascending or descending.â

âHow do you do that?â Chet questioned.

âBy varying the amount of ballast, or weight carried in the form of sandbags,â the pilot explained. âThe more ballast dumped overboard, the higher the balloon will go. To descend, we simply release some of the gas from the bag by means of a valve.â

âJust one thing,â Joe put in. âIf we manage to reach Hextonâs castle, how do we keep from floating right on past it?â

âBy using a length of rope attached to a grapnel,â Frank replied. âWeâll lower it as we approach the castleâand hope it catches somewhere on the wall. This will act as a mooring. Then we can slide down the rope.â

Chet took a deep gulp.

âObviously,â Frank continued, âwe canât keep the balloon moored there. Hextonâs men would spot it sooner or later. So, after weâre down, weâll release the grapnel.â

âThen Iâll sail the balloon a short distance away and land,â McHugh added. âWith your approval, Iâll ask one of the club members to help us. He can drive the lorry containing the launching equipment and assist in our take-off preparations. Later, he can rendezvous with me at the landing spot.â

The boys thanked McHugh and drove back to Clydeâs office.

âA report that will interest you chaps came in while you were gone,â the inspector said. âAn Ianburgh resident said he was involved in a minor automobile accident several hours ago. It happened on a road north of here. According to the report, it was a near head-on collision. Luckily, both drivers jammed on their brakes and merely smashed bumpers.

âThis fellow stated that the other driver seemed in a devil of a hurry. He simply backed away and sped off in his sports car.â

âSports car!â Frank exclaimed. âDid the other driver get its license number?â

âYes,â the inspector replied. âIâve checked it out. The car belongs to a chap named Ross.â

âThe steward we chased into the hangar!â Joe exclaimed.

âAnd another thing,â Inspector Clyde said. âThe accident occurred not far from Hextonâs castle.â

âIâm not surprised,â Frank mused. âRoss could have been on his way there from Prestwick.â

The boys were eager to get their balloon trip under way. Weather conditions the next night were unsuitable for the venture. But on the following night, McHugh telephoned the Hardys at their hotel room that, in his estimation, conditions were ideal.

âThe way I calculate the winds, lads,â he said, âwe should take off from a point about five miles southeast of Hextonâs castle. Iâm familiar with the area, and know several open fields that will serve our purpose.â

âGood!â Frank replied. âWeâll meet you in a few minutes.â

Frank relayed the message to the other boys and all checked the equipment they would takeâ miniature tools, two-way radios, and pencil flashlights.

McHugh had telephoned his fellow club member and soon the lorry containing the balloon and launching equipment was at the door. McHugh was in his own car and the young sleuths hopped in with him. About two hours later the pilot pointed to a clearing just off the road.

âThereâs a good spot,â he announced.

The boys helped to unload the balloon and set up the equipment to inflate it. Makeshift moorings were established to prevent the craft from floating away. Soon a large, spherical, gas-filled bag was looming over their heads, tugging gently at the mooring lines. McHugh and the boys climbed into the gondola and prepared to launch.

âAye, the surface winds are very light,â McHugh observed. âThatâll make our attempt to moor at the castle much easier.â

As they rose slowly into the air, Chet watched the ground slip away. âHey!â he declared with a wide grin. âThis isnât bad at all!â

A half moon in the night sky provided enough illumination for them to distinguish the terrain below. McHugh varied the altitude by dumping ballast and manipulating the gas-relief valve. The balloon altered its track slightly with changes in wind direction.

More than an hour passed, then Joe pointed directly ahead. âThere it is!â

The medieval structure, turrets looming skyward, presented a ghostly image in the dim moonlight. As they drew near it, Chet called attention to a far corner of the courtyard.

âLook!â he said. âA light! Seems to be coming from one of the castle windows.â

âNo more loud talking,â Frank ordered. âWeâre getting close. Help me lower the grapnel line over the side.â

Slowly the balloon drifted toward the castle. The pilot released gas and eased down to a lower altitude. Just then a sharp, metallic sound pierced the night air.

Ping!

âThe grapnel just made contact with the castle wall,â Frank observed.

âWhatâs that?â Chet whispered as he and the Hardys heard a faint scraping sound.

Frank peered over the side of the gondola. âThe grapnel is being dragged up the side of the wall,â he murmured. âIt isnât catching hold.â

They floated over the courtyard toward the opposite wall. With a lurch the balloon came to a halt.

âWeâve made it,â Joe whispered excitedly. âThe grapnel caught.â

âSo far so good,â Frank said tensely. âNow, over the side and down the rope. Iâll go first.â

âGood luck, lad!â the pilot called.

The boys waited for a moment to make certain the coast was clear. Then Frank eased himself over the side of the gondola and got a tight grip on the line. He hung precariously above the ground for an instant, then began to slide down.

Lowering himself gently onto the stone rampart, he peered through the darkness and listened. He then signaled for Joe and Chet to follow. When they were down, they freed the grapnel. The balloon drifted off into the darkness.

The three groped their way along, finally coming to a flight of stone steps. Frank cautiously led his companions down the stairs into the courtyard below.

âThereâs the light I spotted from the air,â Chet whispered, pointing across the courtyard.

âAnd the door right next to it is partially open,â Joe observed.

The boys crept forward slowly until they reached the door. Frank eased it open wider. Peering inside, they saw a long, dimly lighted corridor which extended deep into the castle. It was lined with suits of armor mounted on low, wheeled platforms.

âI donât see anybody around,â Joe whispered. âLetâs go in.â

At intervals along the corridor were large wooden doors with massive iron hinges. As the young sleuths neared the end, they heard muffled voices coming from a room. Its door was slightly ajar. Slowly they stalked toward it and Frank looked inside.

Clustered around a huge oak table were Hexton, Vordo, Bleeker, Arnold, Ross, and the short twins.

Hextonâs voice carried through the opening. âNow get this straight, Vordo. You all know the layout of Nairn Loch Manor?â

âEvery detail,â Vordo replied.

âNo mistakes,â Hexton said harshly. âYou especially, Bert and Lou.â The twins nodded.

âThen itâs all set,â Hexton said. âDay after tomorrow weâll have in our hands the most valuable collection of jewels in Scotland!â

Frank stiffened. So Hexton did plan to steal the Nairn Loch collection before it went on display!

The men stood up to leave, their chairs scraping on the stone floor. Instantly Frank motioned Joe and Chet to retreat down the corridor. Chet hesitated before a suit of armor.

âWhat are you doing?â Joe whispered.

âGetting myself a weapon.â Chet began to tug at a mace.

A metal gauntlet pulled loose and crashed to the stone floor. The sound echoed through the corridor like a burst of thunder. The door creaked open and the men sprang from the room.

âW-why, itâs those snoopers!â Vordo bellowed in surprise.

âGet them!â Hexton commanded.

When the men lunged at the trio, Joe caught Arnold with an uppercut that sent him spinning across the corridor. Frank pushed a suit of armor from its platform, directly into the path of the UGLI men.

âWatch out for Vordo!â he yelled at his brother.

Joe whirled to see Vordo picking up the gauntlet. He flung it at the young sleuth. The heavy object grazed Joeâs head, stunning him.

Meanwhile, Chet was leaping behind one platform after another, pushing suits of armor into the paths of Bleeker and Ross, who were lunging at him. The stout youth grabbed a lance and charged the men.

âLook out!â Bleeker howled.

Chet continued his gallant charge, with Bleeker and Ross running just inches ahead of the point. But the lance proved too cumbersome. The tip lowered to the stone floor, throwing up sparks. Chet stumbled and the two men were quickly upon him.

Arnold, meanwhile, recovered from Joeâs uppercut and ran to help Hexton and Vordo, who were grappling with Frank. Three adversaries proved too much and Frank was finally overpowered.

Joe gradually regained his senses and scrambled to his feet. Hexton glared at them.

âHow did you get in here?â

âFigure that out for yourself!â Frank snapped defiantly.

âWhat now?â Vordo asked Hexton.

The magicianâs decision came quickly. âWeâve no time to waste,â he said. âLetâs take these sons of Fenton Hardy and their friend through the secret passageway to my storeroom. Weâll keep them around as insuranceâin case we run into any trouble.â

âIâll go ahead and open the door,â Bleeker volunteered.

The boys were frisked and the tool kits were removed from the secret pockets of their jackets. Their miniature short-wave radios were also taken.

âLeave âem their flashlights,â Hexton said, and added with a sardonic chuckle, âItâll help âem see what a lot of trouble they got themselves into.â

The three prisoners were prodded along the corridor, then through a camouflaged opening in the wall. Single file, they walked down a long, stone staircase and through a secret passage beyond. The boys could see nothing of their surroundings other than what Vordoâs flashlight picked out of the darkness, but they felt a clammy dampness in the air.

âHere we are,â Hexton said finally.

Directly ahead was a huge iron door. The hinges squeaked as Vordo pulled it open.

âGet in there!â Bleeker growled.

The Hardys and Chet were shoved into a large dungeon-like room. Scattered about were various devices that Hexton had developed for his magic shows.

âWe canât keep âem here!â Vordo warned. âThe lock on this door is so old it wonât work!â

âI know,â Hexton replied. âBut Iâve something else in mind.â

He pointed to an oversized trunk, standing on end. It was constructed entirely of heavy steel, and held together with large rivets. Near the base were several air holes.

Hexton removed the three massive padlocks that secured the trunk. âPut them in here,â he ordered. âTheyâll never escape from this!â

âYou canât do that!â Joe shouted. âThere isnât enough room!â

âShut up!â Vordo snarled.

The magicianâs cohorts pushed the boys toward the trunk and forced them to step inside.

âThis will give you time to regret that you ever thought you could outsmart the Incredible Hexton!â the magician declared, uttering a spine-chilling laugh.

Seconds later the trunk was slammed shut, and the Hardys and Chet were locked in inky blackness!

CHAPTER XVIII

Chetâs Big Assist

âWEâLL never break out of here!â Chet told the Hardys.

âIt does look pretty hopeless,â Joe admitted glumly.

âThink!â Frank commanded. âWe have to come up with something!â

He and the others took the pencil flashlights from their pockets and played the beams around the small steel prison. They saw no chance of escape.

âHexton was right,â Frank conceded gloomily.

âHey!â Chet burst out. âTurn your flashlights this way.â

He began to explore the top and sides of their enclosure. Finally he said, âHmm. There might be a way out of hereââ

âNo kidding,â Joe declared. âIn case youâre thinking of a magic trick to make us fit through the keyhole, forget it.â

âNothing short of an acetylene torch can solve our problem,â Frank put in. âThese trunk walls must be an inch thick.â

âI know,â Chet said, âbut look at those rivets.â

âWhat about them?â

âThe ones along the top,â Chet explained, âare just a bit shinier than those along the sides.â

The Hardys nodded in agreement.

âDo one of you have a pocketknife?â Chet asked. âOr did the UGLIâs take it?â

âThatâs something they missed,â Frank answered. âHere.â

He and Joe looked on quizzically as Chet placed the point of the blade against the edge of a rivet at the top of the trunk. Clenching his fist, he hammered against the end of the knife. After several sharp blows, the rivet turned slightly.

âEureka!â Chet shouted. âI was right!â

âHow about letting us in on whatever youâve found?â Joe pleaded impatiently.

âThe top of this overgrown trunk,â Chet explained, âis attached by false rivets.â

âFalse rivets?â Frank queried.

âYes,â his chum replied. âActually theyâre not solid rivets, but are cut through in the middle and threaded so the ends can be screwed together just like a regular nut and bolt.â

The Hardys looked at Chet in amazement. âHow did you happen to know about this?â Frank asked.

âWhen I began to study magic,â Chet replied, âI read a book about famous magicians. A few, like Houdini, were also great escape artists. The book described false rivets as one of the tricks they used.â

Chet continued to pound his fist against the knife. Soon the rivet head was loose enough to turn by hand. After several twists, it came apart.

âThis is the hard way of doing it,â Chet said. âThe escape artist uses a special wrench which fits over the rivet head. Thatâs why these are shinier than the others.â

âBoy, your interest in magic really paid off,â Frank remarked with a grin.

âBut why would Hexton lock us up in something we could escape from?â Joe asked.

âHe never expected any of us to figure it out,â Frank surmised.

By this time Chet had loosened three of the rivet heads. Frank and Joe each took a turn working with the knife. The job was hard and tedious. Several hours passed before the last of the false rivets was unfastened.

Grinning in satisfaction, the boys pushed up against the metal top. It broke free and toppled to the floor with a loud bang. Elated, they quickly scrambled out of the trunk and stretched their aching bodies.

âGreat going, Chet,â murmured Joe.

Frank echoed this, then beckoned the others to the door. The lock was, indeed, defective and the boys had no difficulty opening it. They stepped outside into a small vestibule. There they saw the entrances to several passageways.

âLeaping hyenas!â Joe exclaimed. âWhich way do we go?â

âGolly!â Chet gasped. âDo you fellows remember which passage Hexton and his men brought us through?â

âI didnât realize there was more than one,â Frank admitted. âIt was too dark to see.â

âThis is like a maze.â Joe shook his head in bewilderment.

Using his flashlight, Frank led the others through one of the passageways, up flights of stone steps, through places where the ceiling was so low that they almost had to crawl, then along several sharp turns that completely confused them.

âWeâre not getting anywhere,â Chet complained.

âThis castle must be honeycombed with secret corridors,â Frank said.

He swept his flashlight beam ahead and saw that the passage branched off in three different directions. They went down the middle one for what seemed like an hour, but could only have been a few minutes. It came to an abrupt end. They were facing a blank wall.

âNow what?â Joe sighed.

âWhat I wouldnât give for a road map of this place!â Chet mumbled.

The boys backtracked, then turned down the left passageway. More stone steps led them deeper and deeper inside the cellar of the castle.

Presently Frank stopped short. âWait a minute,â he ordered. âDo you fellows notice anything?â

âNot me,â Chet said.

âI donâtâSay!â Joe replied. âThe air is getting real damp and clammy!â

âRight,â his brother agreed. âJust like it was in the passage to Hextonâs storeroom. Maybe weâre on the right track.â

The boys continued on and made several sharp turns. Frank pointed his flashlight ahead and uttered a cry of dismay. They stood before the iron door to the storeroom, the very same place from which they had started!

At that moment they heard muffled footsteps. Frank snapped off his flash. From a distance, beams of light played across the iron door. The trio flattened themselves against the wall where it angled away from a little alcove.

Frank leaned closer to Joe and Chet. âIt must be a couple of UGLIâs to check on us,â he whispered. âWatch where they come from. Itâll have to be the passageway that will lead us out of here.â

The men drew near. Would they see the escaped prisoners? Fortunately the men failed to notice the Hardys and Chet in the darkness and entered the storeroom.

âHey!â came a shout almost immediately. âTheyâre gone!â

By this time the boys had dashed down the corridor, along which the men had come.

âThere they go!â one of Hextonâs pals yelled. âAfter âem!â

Frank, Joe, and Chet had a good head start. They ran as fast as the narrow, winding passageway would permit. Behind them swept the beams from the flashlights of their pursuers.

Ahead, the tunnel forked out into two flights of steps. âOh no!â Joe cried despairingly. âWhich way?â

Frank searched the steps with his flashlight. The ones on the left were more worn. âThis way,â he said as the sound of the pounding feet behind them grew louder.

The three boys raced up the long flight of steps and down another corridor, but soon realized that their choice was wrong. The passage ended in a blank wooden wall!

âThere must be a way out!â Frank declared. He picked up a loose stone and hammered against the wall. âListen!â he said. âThis wall doesnât sound solid. It must have a secret panel. Quick! Help me get it open.â

Joe and Chet pushed against the wall with all their strength.

âIt wonât budge!â Joe gasped.

The sounds of their pursuersâ approach pounded in their ears. As the trio braced themselves for the oncoming struggle, there was a sudden grinding noise in the wall. They turned to see a panel slowly opening. A man, holding a flashlight, poked his head from behind the secret door. The boysâ eyes widened in astonishment.

Kenneth Dell!

CHAPTER XIX

âPrepare to Ditch!â

âFRANK! Joe! Chet!â Great Circleâs security chief exclaimed.

Behind him in a hallway stood Inspector Clyde. âI say!â he exclaimed. âWhat are you chaps doing in there?â

Before the three startled boys could reply, their pursuers rushed up. They almost collided as they came to an abrupt halt. Bug-eyed, Hextonâs pals gazed at the lawmen, reinforced by other police. The UGLIâs whirled about and ran back through the passageway.

âCome on!â Frank shouted. âAfter them!â

The boys rapidly gained on the men. Frank, in the lead, caught the nearest one with a flying tackle. He fell against the pair ahead, causing them to topple like a row of dominoes. There was a brief struggle while Inspector Clyde and several Scottish police officers rushed up to help the boys subdue their captives.

The UGLI men were handcuffed and led away by the police, while Frank, Joe, and Chet followed Dell and the inspector through the open panel into the main hall of the castle. They noticed it was already daylight, and Chet yawned sleepily as the group went to sit down in a huge library.

âWeâre amazed to see you, Mr. Dellâand you, Inspector,â Frank said. âHow did you get in without being caught?â

âFirst, let me tell you why I came here,â Dell said. âSKOOLâs work is paying off at last. Frank and Joe, your father has almost single-handedly cracked UGLIâs operations in all European countries except the British Isles, and in the United States.â

âThatâs great!â Frank exclaimed.

âIt sure is,â Joe added. âAnd the mystery of the undercover work here isâwell, half solved.â

Clyde said that shortly after dawn McHugh had telephoned him, fearful something must have happened to the boys. âI gathered a few constables together and came straight here.â

âLucky break for us!â Joe remarked.

âAt the castle gate,â Clyde continued, âwe met a most unsavory-looking character. One of the constables recognized him as a thief wanted by the police in Glasgow. He resisted arrest and ran into the castle. We chased him.â

Clyde told the boys that inside he and the constables had encountered four other men who also resisted arrest. They were Arnold, Ross, and the twins.

âI questioned them,â he said, âbut they refused to talk.â

âWhat about Hexton, Vordo, and Bleeker?â Frank asked.

âApparently all three got away,â the inspector said. âTell us, what happened to you?â

Joe briefed the men, then said, âIâll bet Hexton and the others are on their way to Edinburgh. Last night we overheard them discussing plans to steal the jewels at Nairn Loch Manor before itâs opened to the pubââ

Joe stopped speaking at the sound of a faint hissing and turned abruptly. Then he burst out laughing and pointed to Chet, who had fallen asleep in an easy chair. His hands were folded on his stomach and he snored lightly.

âYou all deserve a good sleep,â Dell suggested, but the Hardys were too excited to accept the idea. There were still many questions to be asked.

âHow did you find the entrance to the secret passageway?â Frank wanted to know.

Dell replied, âWe were starting to search for you when a pounding sound came from the other side of the wall. All of us suspected it might be you signaling for help and hunted for a secret panel. I discovered that by moving the left gauntlet on one of the suits of armor in the main hall, a portion of the wall began to open!â

âAnd thank goodness,â said Joe. âWe thought that wall was the end of the line for us.â

âSomewhere in this castle,â Frank spoke up, âthere must be evidence of Hextonâs espionage setup. Have you found it?â

âNo,â Dell replied. âHavenât had time to look.â

âLetâs see if we can find it,â Joe suggested.

No one had the heart to awaken Chet, so they left him. Inspector Clyde offered to investigate the library. Dell and the boys started down the adjoining hall to examine various other rooms.

The Hardys looked into several, but saw nothing to indicate espionage paraphernalia. At the end of the hall, they found themselves facing an enormous faded tapestry.

âMaybe this hides something,â Frank said.

He and Joe slipped behind the hanging and found a large double door which opened inward. As they entered, the Hardys were awed by the vastness of the room. The ceiling arched high above their heads, and lancet windows spilled bright sunlight onto the floor. At one end was a huge map of the world with colored pins stuck in various cities.

âUGLIâs centers of operation!â Frank exclaimed. âIf Dad missed any, this will tell him where else to look!â

In the center of the room stood two oak tables. There was an elaborate radio setup on one. Joe whistled. âPowerful baby!â

On the other table were several metal cases, sealed without any visible means of opening.

âTrick boxes,â said Frank. âOne of Hextonâs specialties.â

Dell walked in as the boys looked them over and tried pressure in several places. Nothing worked. Then Frank had an idea. He turned one box toward him and the side slowly opened.

Joe grinned. âHardy, the magician!â âNo,â said Frank. âElectric eye.â He moved the other two cases and each opened in the same way, revealing rows of drawers.

In the first one the boys found packages of microfilm and microtape, each labeled with a code tag.

âTells where they came from and where theyâre going,â Frank guessed. âHexton brings them here. UGLI operators make the pickup and take them to countries hostile to the United States and other democratic powers.â

Dell frowned. âThese are probably films of secret plans and drawings of highly classified material.â

âHereâs the roster of UGLI operators!â Joe exclaimed, riffling through a notebook. âProbably these names are in code.â

âDoesnât matter,â said Frank. He held up a red leather volume. âHereâs the codebook!â

âWell,â said Inspector Clyde, entering the room, âthat will come in handy when itâs time to round up those UGLI blighters. I saw the tapestry hanging awry and guessed you might have found a hidden door.â

He stood in amazement at the boysâ discovery. âWhat a treasure for Scotland Yard, the FBIââ

âAnd SKOOL,â Joe spoke up. âUGLI, the biggest undercover subversive operation in the world, cracked wide open!â

Frankâs enthusiasm was dampened by the fact that some of UGLIâs top men were still at large. âUnless we catch them, theyâll start a new operation somewhere else.â

âThatâs true,â Clyde said, and the others agreed.

âThen letâs find them!â Joe cried.

At that moment a constable ushered in McHugh.

âI returned to Ianburgh to get my plane,â the pilot said, âand flew âer back here. Thought I might be a wee bit oâ help.â He had landed on an open field close to the castle, he told them.

âThatâs great!â Frank replied eagerly. âWill you fly us to Edinburgh?â

âCertainly.â

McHugh was introduced to Dell. The pilot grinned. âMan, ye got a couple oâ fine detective lads here,â he said. âWell, Iâm ready to start.â

Inspector Clyde decided to stay at the castle. âIâd better remain here in case something important pops up on this end.â

Frank and Joe roused Chet, who rubbed his eyes and stubbornly demanded breakfast.

âCome on!â Joe urged. âWeâll grab a bite when we land. Chet, wait till you hear what we found!â

This roused the stout boy and he followed the Hardys and Dell to the plane. All the boys cat-napped during the flight, and later at Edinburgh Airport stoked up on bacon and eggs. Then, while McHugh stayed with the plane, the boys and Dell went to the local police office to reveal Hextonâs daring scheme of robbery the next day.

The constable on duty, a plump man with reddish hair who introduced himself as Officer Watson, was highly indignant. âImpossible! Thieves could not get within five hundred feet of the Manor without being challenged!â

âDonât underestimate Hexton,â Dell warned. âHeâs an extremely clever crook.â

âNow that he knows weâre after him,â said Frank, âhe might very well pull the robbery today.â

âIs Nairn Loch Manor far from here?â Joe inquired.

âOh, just a few minutes by car,â Watson replied.

âWill you come with us?â Dell asked him.

âWell-all right. But I tell you, this man Hexton hasnât got a chance!â

They climbed into Watsonâs car and soon arrived at the large, fortress-like structure built of stone. The windows were heavily barred, and the thick oak doors were secured by large iron bolts.

Watson showed his credentials, then introduced his companions. He asked to see the custodian, Angus Hamilton. The custodian scoffed when he heard about Hextonâs intentions. âImpossible! Utterly impossible!â he asserted. âThe Manor is too well guarded.â

âWhat about burglar alarms?â Frank asked.

âA complete system is now being installed,â Hamilton answered. âIn fact, the Manor will not be opened to the public until itâs completed.â He grinned. âNo, Iâm afraid your fears are unwarranted. This Hexton fellow would have to render himself invisible to get onto the premises.â

âIâm not sure he couldnât do just that,â Chet mumbled.

âMay we see the jewel collection?â Frank requested.

âIâll be happy to show it to you,â Hamilton said with pride.

He led them down a long hallway. At the far end was a heavy oak door, flanked on each side by a guard. With a large black key the custodian unlocked the door. He ushered the Hardys and their companions into the chamber.

âYou gentlemen,â Hamilton said, âare about to see one of the most splendid collections ofââ His voice trailed off, and his face turned ashen. âThe jewels!â he gasped. âThe jewels! Theyâre gone!â

The Hardys ran to the glass cases in which the treasure had been kept. Except for a gold crown and several scepters, the cases were empty!

âB-but how?â the custodian cried, almost in a state of panic. âI checked the collection just a little while ago!â

The local constable took command of the situation and questioned the guards. None of them had seen any suspicious strangers in the area. A quick inventory revealed that all the smaller, but extremely valuable jewels were missing.

âHexton left the crown and scepters behind because theyâre too bulky,â Frank surmised.

âWhatâs your guess, Mr. Dell,â asked Joe, âas to the way the thieves got in here?â

Dell turned to the custodian. âAre there any architectural plans of the Manor available?â

âIndeed yes. I have them in my files. But if youâre looking for a secret passageway, you wonât have any luck. Iâve studied those plans thoroughly.â

Watson, meanwhile, had telephoned his office and ordered his men to close off all roads leading out of Edinburgh. Also, airports and piers throughout the country would be alerted at once.

âDo you think Hexton is headed back to his castle?â Joe asked.

âIf so,â Frank said, âheâll find quite a welcoming committee waiting for him. But now that he knows the police were there, Iâd say heâll stay away from the place.â

âWeâd better phone Inspector Clyde about the robbery,â said Chet. But when Joe tried to do this, he found there was no telephone at the castle.

âWeâd better fly back there right away,â Frank said.

Dell announced he must return to the United States. âIf Hexton comes there, Iâll be on hand to pursue that part of my assignment.â He said good-by and went off in a taxi.

Watson drove the boys to the airport, then went back to his office. As the young detectives hurried toward the trimotored plane, they saw that the pilot was already seated in the cockpit. Frank signaled to him and McHugh responded with a not-too-enthusiastic wave of his hand.

âSomething seems to be troubling him,â Joe observed as they climbed into the cabin and slammed the door. The pilot started the engines and the plane began to taxi toward the runway for take-off.

Frank walked up to the cockpit. âWhat seems to be the matââ He stopped abruptly and gasped. Crouched in the seat next to McHugh was Stony Bleeker! He held a gun pointed at the pilot.

âGet back into the cabin!â Bleeker commanded.

Frank turned to see two men emerge from beneath a tarpaulin at the rear. Hexton and Vordo!

âItâs nice of you boys to accommodate us like this,â the magician said with a smirk. âWe happened to be in need of fast transportation.â

âW-when did you get aboard?â Joe stammered. âWe thought youâd be a long way from Edinburgh by this time!â

âOur car broke down on a back road near the airport,â Hexton snapped. âThen Bleeker spotted this plane and we decided to hitch a ride.â

âWhere to?â Joe demanded.

âWeâre all going for a nice little flight to Ireland,â the magician announced sarcastically.

âI told you I can noâ make it there!â McHugh shouted. âWeâve noâ enough fuel!â

âDonât try to fool me!â Bleeker growled. âYour gauges show full tanks!â

âThe gauges havenât worked for weeks!â the pilot insisted. âI calculate my fuel consumption by the amount of time I fly. And I tell ye, we noâ have enough fuel to make Ireland!â

Hexton let out a spine-chilling laugh, and eyed the Hardys and Chet. âYour pilot will have to think up a cleverer trick than that, because I donât intend to go back to my castle and meet your Inspector Clyde!â

âHow do you know about that?â Frank asked.

The magicianâs weird, piercing eyes focused on the boys with a fixed stare. âBleeker stayed behind when Vordo and I left for Edinburgh,â he replied. âHe was there when the constables arrived, and escaped without being seen. Of course he came straight to Edinburgh to warn us.â

âIncidentally,â Frank put in, âhow did you manage to pull off the Manor robbery?â

âShut up!â Vordo growled. âYouâre asking too many questions!â

âNo, no, Vordo. I donât mind telling them,â Hexton said boastfully. He reached into his jacket pocket and withdrew a folded piece of parchment. âThis,â he said, âis the architectâs original plan of Nairn Loch Manor. There are copies, of course. But this is the only one showing the secret passageway.â

âThe passageway,â Frank said, âthat leads into the chamber where the jewel collection was kept.â

âYes, and very convenient for me,â the magician replied smugly, âespecially since its entrance is located in a hill nearly a quarter of a mile away. As for this,â he added, tapping the parchment, âit used to be on display in a small private museum, but a master key and a little sleight of hand put it in my pocket.â

As the plane continued on course, the Hardys noticed that their captorsâ jackets bulged and a sealskin pouch jutted from one of Hextonâs pockets. Undoubtedly it contained the stolen jewels!

A few minutes later McHugh shouted another warning. âWeâre leavinâ the coast! We can noâ go any farther!â

Frank gazed below. They were passing over the west coast of Scotland and heading out over the Irish Sea. Just then the port engine sputtered. Seconds later the center and starboard engines began to quit.

McHugh whirled the plane in a tight turn back toward the Scottish coast. Leveling the craft out on a reciprocal course, he tightened his grip on the control wheel.

Frank and Joe stared at the propellers as they windmilled noiselessly in the powerless glide. Below them was the choppy surface of the Irish Sea.

âI can noâ reach land!â McHugh shouted. âWeâre goinâ down. Prepare to ditch!â

CHAPTER XX

Desperate Flight!

MCHUGH flicked his radio transmitter to 121.5 megacyclesâthe international distress frequency.

âMayday! Mayday! Mayday!â he shouted into the microphone. âThis is TrimotorâVictorâVictorâFox! About twenty miles southwest oâ Skip-ness radio! Lost all power! Have tâ ditch!â

Hexton and his cohorts were pale with fright as they watched the plane sink closer to the water.

âQuick, lads! Jettison the cabin door!â McHugh ordered.

Near the door was a red handle. Joe dashed to it and gave a sharp pull. As the door shot off into space, there was a thunderous rush of air through the cabin.

âSit with your backs against the forward bulkhead!â the pilot yelled. âClasp your hands behind your heads and brace yourselves!â

Everyone took ditching positions. The wait was nerve-shattering. Finally the plane hit the water. It bounced off the surface on first contact, then nosed down into the choppy sea with a violent impact. Water gushed into the cabin. As the boys recovered from the shock, Frank turned to see Hexton pushing himself out through the cabin entrance.

âWeâre sinking fast!â Joe yelled.

âLook!â Chet shouted. âMcHughâs unconscious!â

âSo are Vordo and Bleeker!â Joe added.

âWe must get them out of here!â Frank declared. âIâll take McHugh! You two grab the others!â

Clutching the unconscious men, the boys edged their way to the cabin entrance and pushed themselves clear of the sinking aircraft. They were not too far from land and began swimming.

Joe, who was dragging Vordo along with him, looked toward the shore just as Hexton reached it. The magician stumbled ahead and disappeared into the tall grass.

âHextonâs getting away!â Joe shouted.

âWeâll have to let him go,â Frank replied. âWe canât let Vordo and Bleeker drown.â

Chet, meanwhile, was too winded to speak, as he swam doggedly on with his heavy burden. Bleeker was a dead weight. The boys had almost made it to shore when a motor launch of the Air-Sea Rescue Service sped toward them.

âWe received your distress signal,â one of the crewmen shouted as the boat pulled alongside. âAnybody missing?â

âNo,â Joe shouted back. âOne man made it to shore.â

Vordo and Bleeker began to recover as they were hauled aboard the boat.

âWeâd better tie up these two,â Frank said. âTheyâre jewel thieves.â Rope was produced and the prisoners bound.

Joe and Chet helped McHugh, who groaned and slowly got to his feet. Grief-stricken, he watched the tail of his plane disappear beneath the surface of the water in a bubbling sea of foam.

Joe began going through the prisonersâ pockets. âLook!â he cried, holding out several sealskin pouches. They were crammed with jewels.

âFirsthand evidence,â said Frank. âHexton must have the rest. Now that his espionage work has been destroyed, he probably figures on living off the haul he made today.â

âLetâs ask these UGLIâs a few questions,â Joe suggested. He turned to Vordo and Bleeker. âHow did you kidnap our father?â

The two men glared. âYouâre getting nothing out of us!â Vordo snarled.

âThatâs tellinâ em, Vordo!â Bleeker snapped. âToo bad the mirror Hexton had you put on the road didnât work out and that Lou missed with that sandbag. Weâd have been rid of these snoopers long ago! And itâs a shame they have a crackerjack pilot who safely landed their plane after you loosened the fuel caps.â

When the rescue ship reached shore, the prisoners were turned over to the authorities. The others proceeded to Prestwick in a car lent to McHugh by a friend. Regretfully the three boys bid good-by to the brave pilot.

âYouâre tops,â Joe added, and Frank said. âOne of the best sports I ever met!â Chet nodded.

McHugh smiled. âYouâre the finest lads I ever knew. Come again sometime and have a ride in my new plane.â

âWeâll do that,â Chet answered.

After the pilot had left them, the boys went for a bite to eat. Joe expressed his frustration that Hexton had escaped.

âWhere do you think heâll go?â Chet asked. âIreland, like he said?â

Frank shook his head. âMy guess is New York.â

Joeâs eyes lighted up. âAnd maybe on Flight 101! It leaves tomorrow morning.â

Chet snorted, âAn UGLI secret agent on Flight 101!â

âWeâre going to be on board, too,â said Frank. âIf heâs there, weâll nab him.â

The boys informed Inspector Clyde of their plan. They could hardly wait to take off. Next morning they watched intently as the passengers filed aboard.

âHey!â Joe exclaimed, nudging his brother. âThereâs that same man we saw on our last flight to New Yorkâthe one with the dark glasses and whiskers and cane.â

âWell, he canât be Hexton in disguise,â Frank commented. âThis manâs heavier set.â

âI donât see anybody that looks like Hexton,â Chet lamented.

They observed another elderly bewhiskered man with a cast on his left leg hobble up on crutches. A steward helped him into the plane.

The boys were the last to go aboard. During the flight the boys studied the other passengers but saw nothing suspicious.

When the wheels screeched down at Westboro, Joe stretched his arms wearily. âGuess we drew a blank this time.â He sighed.

At the Great Circle Airways ramp, the passengers began to debark.

âLetâs keep our seats until everybodyâs out,â Frank whispered. âWatch carefully.â

The plane emptied until only the two elderly men, the three boys, and the steward were left. The man with the cast eased himself onto his crutches and started down the aisle.

Joe stiffened. âHey! Did you see that?â he whispered excitedly. âThat old man was walking on his injured leg! Iâll bet heâs a fake.â

âI saw it too,â Frank replied. He bolted out of his seat and called, âWait a minute! We want to talk to you!â

The man stopped abruptly. Then he swung one of his crutches at Frank as the youth darted toward him. The other elderly man sprang from his seat and dealt him a blow with his cane that sent him stumbling up the aisle.

âSteward,â bellowed the man with the cast, âkeep these guys away from me!â

âThat voice!â Joe yelled. âItâs Hextonâs!â

The steward was about to pounce on Frank, when Chet cried out, âThis manâs wanted by the police!â

Frank leaped at Hexton as the magician again swung his crutch. The young sleuth ducked and lunged forward, crashing into his opponentâs midriff. As Hexton fell, his cast struck a seat and broke open. From it, a cascade of jewels spilled into the aisle. At the same moment several men poured in through the passenger door.

Among them was Kenneth Dell. âLooks as if you fellows already have things under control.â

Chet picked up two sections of the cast. âItâs light plastic,â he said, âand looks as if itâs made to come apart.â

Frank yanked the magician to his feet, and whipped a wig from the manâs head. Then he ripped off Hextonâs false eyebrows and whiskers.

Joe whistled. âAmazing what a little disguise can do to change a manâs appearance!â

âYouâre right!â said the other elderly man.

âWe want to thank you, sir, for your help,â Joe said gratefully.

âThatâs all right, Joe,â the man replied, chuckling.

Joe! As the boys looked on in amazement, the man removed his dark glasses and a false beard.

âDad!â the young sleuths exclaimed, overjoyed to see their father.

Then Frank whispered to him, âSo you were the secret agent for SKOOL on Flight 101!â

âYes,â Mr. Hardy said quietly. His âagedâ slouch was gone, and he pulled himself to his full height. âSorry to keep my whereabouts a secret. But the job was so dangerous I couldnât risk telling anybody where I was.â

âYou never were in South Africa?â

âNo.â

Hexton was livid. âYou havenât heard the last of me!â he snarled.

âSave your breath,â Joe retorted. âYouâll need it when the authorities begin questioning you and the other members of UGLI.â

Federal agents arrived to take custody of Hexton. The boys learned that Mr. Hardy had cabled Dell to have the agents on hand because he suspected who the âinjuredâ passenger was.

âI wanted him captured on U.S. soil,â the detective said.

âTell us, Dad,â Frank asked eagerly, âhow Hexton managed to spirit you away in that vanishing-man device?â

âIt was quite a simple trick,â Mr. Hardy explained. âThe bottom of the plank I was strapped to was a highly polished mirror. After setting it in the frame, the frame was rotated so the mirror side of the plank was angled toward the audience. In this position, it reflected the roof of the enclosure, which was made of the same material as the draperies forming the rear wall. To an observer it looked as if the plank had vanished, including the subject. Meanwhile, a man of the same size and build wearing the identical clothes appeared from the wings.â

âThat was Lou, then,â said Joe. âBertâs double. Chet, old pal, you were right about the trick.

Chet beamed modestly. âIt was nothing.â

âIn my case,â Mr. Hardy went on, âBleeker was hiding in a secret compartment in the base of the device. When Hexton closed the curtain, he popped up and jabbed me with a needle containing a powerful drug. UGLI members always carry these hypodermics for emergencies. I passed out in seconds.â

âHow did you escape from the lighthouse?â Joe asked.

Fenton Hardy grinned. âI had a lucky break,â he said. âVordo and Bleeker handcuffed me to the metal railing of the spiral stairway, with my hands behind my back. Fortunately I spotted a short piece of baling wire on the floor. It was a tough job, but I managed to get the wire to stick to the heel of my shoe. Then I bent my leg back far enough so I could reach the wire with my fingers.â

âAnd you picked the lock of your handcuffs!â Joe guessed.

âYes,â Mr. Hardy replied. âIt took me hours. Then I sneaked out while Vordo and Bleeker were sleeping and borrowed their dinghy. I had almost reached the mainland when I heard their powerboat coming from the islet. So I capsized the dinghy and swam the rest of the way.â

Frank grinned. âYou hoped Vordo and Bleeker would find it and think you had drowned.â

âExactly,â his father answered. âAt least it would keep them guessing.â

Mr. Hardy then described his investigations of the Great Circle stewards he suspected. âI used several disguises including a blond wig.â

Chet asked him why he had tripped Ross with the cane.

âI thought maybe he had a small package of jewels in his sleeve or under his coat, and it might fall out when he fell. But I was wrong. I also slipped the note into Joeâs suitcase.â

âWhat about Mazer, the pilot of the helioplane?â Joe inquired.

âI believe he was a victim of circumstances,â Dell replied. âThe authorities are going to let him off with a yearâs suspension of his pilotâs license.â

The group got out of the plane and Mr. Dell said good-by. âSee you on the next case, Fenton,â he called, and hurried off.

Frank and Joe fervently hoped they might be included, but first they were called upon to solve the Mystery of the Whale Tattoo.

âNow, fellows,â Mr. Hardy said with a grin, âI suggest we call Jack Wayne and have him fly all us SKOOL boys home.â

âSKOOL boys? What do you mean?â Chet asked.

The secret agent grinned. âI think youâve all earned places in the organization as junior members!â