TOM SWIFT

AND THE MYSTERY COMET

BY

VICTOR APPLETON II

Tom Swift Jr. -. 28

The Tom Swift Jr. Series:

1 Tom Swift and his Flying Lab (1954)

2 Tom Swift and his Jetmarine (1954)

3 Tom Swift and his Rocket Ship (1954)

4 Tom Swift and his Giant Robot (1954)

5 Tom Swift and his Atomic Earth Blaster (1954)

6 Tom Swift and his Outpost in Space (1955)

7 Tom Swift and his Diving Seacopter (1956)

8 Tom Swift in the Caves of Nuclear Fire (1956)

9 Tom Swift on the Phantom Satellite (1956)

10 Tom Swift and his Ultrasonic Cycloplane (1957)

11 Tom Swift and his Deep-Sea Hydrodome (1958)

12 Tom Swift in the Race to the Moon (1958)

13 Tom Swift and his Space Solartron (1958)

14 Tom Swift and his Electronic Retroscope (1959)

15 Tom Swift and his Spectromarine Selector (1960)

16 Tom Swift and the Cosmic Astronauts (1960)

17 Tom Swift and the Visitor from Planet X (1961)

18 Tom Swift and the Electronic Hydrolung (1961)

19 Tom Swift and his Triphibian Atomicar (1962)

20 Tom Swift and his Megascope Space Prober (1962)

21 Tom Swift and the Asteroid Pirates (1963)

22 Tom Swift and his Repelatron Skyway (1963

23 Tom Swift and his Aquatomic Tracker (1964)

24 Tom Swift and his 3D Telejector (1964)

25 Tom Swift and his Polar-Ray Dynasphere (1965)

26 Tom Swift and his Sonic Boom Trap (1965)

27 Tom Swift and his Subocean Geotron (1966)

28 Tom Swift and the Mystery Comet (1966)

29 Tom Swift and the Captive Planetoid (1967)

30 Tom Swift and his G-Force Inverter (1968)

31 Tom Swift and his Dyna-4 Capsule (1969)

32 Tom Swift and his Cosmotron Express (1970)

33 Tom Swift and the Galaxy Ghosts (1971)

From the front: Tom Swift Jr. Realizes one of his greatest ambitions when the U. S. Space agency commissions him to do a comet probe. With his latest invention, the telesampler, Tom hopes to glean unknown scientific facts from the next comet to pass near earth - and even, perhaps, make a manned landing. But his erstwhile enemies the Brungarians are a threat to the daring research project and U. S. Scientific prestige.

Meanwhile, weird unidentified flying objects blazing across earth's skies are causing the U. S. Department of Defense great concern. When Professor Feng, of the University of Heidelberg, gives Tom a strange clue to the UFO's - a clue which dates back to the Middle Ages - the young space scientist is soon caught up in a web o£ danger and intrigue.

How Tom succeeds in solving the complex riddle of the UFO's-just in time for a desperate race with a deadly comet as earth's fate hangs in the balance-makes one of the most tension-packed, thrilling stories in the Tom Swift series.

ILLUSTRATED BY RAY JOHNSON

GROSSET AND DUNLAP © 1966 BY GROSSET & DUNLAP, INC.

All rights reserved published simultaneously in Canada

library of congress catalog card number Ac 66-10287

PRINTED IN THE UNITED STATES OF AMERICA

CHAPTER I

DOOM GLOW

"Look! More fireworks!" Bud Barclay exclaimed.

Dazzling disks of red, blue, and yellow were zooming through the night sky over Lake Carlopa! Bud's pal, Tom Swift, and their two dates stared in astonishment. Tom's blond, blue-eyed sister Sandra murmured, "I thought the show was over!"

The teen-age foursome, which also included dark-haired Phyllis Newton, were at a Fourth-of-July dance on the Shopton Yacht Club terrace. The last skyrocket had exploded only moments before as the band played "Auld Lang Syne."

Now a fresh and startling spectacle was unfolding! Even the musicians stopped playing, awestruck as the brilliant disks swooped, circled, and zigzagged in perfect formation.

Tom's scalp prickled eerily. "Those aren't fireworks!" He gasped. "They're UFO's-unidentified flying objects!"

Phyl Newton shot a wide-eyed glance at the young inventor. "Tom, are you sure?"

"They must be! They certainly weren't launched from the fireworks barge, and they're just like the descriptions in the news stories!"

Recently a rash of UFO sightings had been reported in the newspapers, but few people had taken them seriously. Tom himself had been skeptical of the reports. Now he was seeing the strange objects with his own eyes!

A hubbub of excitement arose on the terrace as the word spread among the spectators.

"I don't believe it!" A woman cried out. "They can't be from outer space!"

A man's voice blurted, "It's no fake-they're really UFO's!"

Bud - a husky young flier and astronaut who like Tom was eighteen-grabbed Sandy's hand. "Come on! Let's look through the telescope up on the balcony!"

"Good idea!" Tom said. He put an arm around Phyl's waist and they hurried through the crowd after Bud and Sandy.

They had just reached the French doors which opened from the yacht-club ballroom when Tom felt a sharp poke in the ribs.

"Hey, big shot! You're the space know-it-all - where'd those things come from?"

The speaker was a red-haired, freckle-faced youth. Tom recognized him as Ranee Gorman, a Shopton High senior who took every opportunity to needle the young inventor.

"Your guess is as good as mine," Tom said with an even-tempered grin.

"Aw now, quit holding out on us." Ranee tried to detain Tom by clutching the lapel of his sport coat. "I'll bet you scientific masterminds at Swift Enterprises launched those UFO's!"

Tom brushed his hand away. "Guess again, pal. But thanks for the compliment."

Ranee's hooting laugh followed them. "It's probably all that hot air from your genius factory that keeps 'em up there I"

Bud scowled as the foursome hurried toward an inside staircase that led up to the balcony. "That wise guy! Why didn't you sock him, Tom?"

"Forget it. Ranee likes to have his little joke."

"He's just jealous of Tom," Sandy said with a smile of pride at her famous brother.

On the balcony, which was fitted out like a ship's bridge, they found an excited knot of people clustered around the telescope. All were clamoring for a view of the UFO's, which were still wheeling overhead like colored meteors.

Tom's group waited impatiently for a turn at the telescope. Bud grumbled, "Those things will be gone by the time we get a look!"

Just then an announcement came over the public-address system: "Tom Swift, please go to Swift Enterprises at once!"

"I wonder what's up?" Sandy asked.

"We can find out on the way," Tom replied. "Come on, let's go! If we get there fast enough, we may be able to pick up the UFO's on the megascope space prober." This recent invention of Tom's was an electronic telescope of potentially infinite range.

The four teenagers hurried down to the main floor. As they dashed out to the yacht club's parking lot, the weird sky objects continued their brilliant display. The dark blue waters of the boat basin sparkled with the reflection of their dazzling colors.

Tom's party climbed into Bud's red convertible and in a few moments they were speeding off along the highway that led to Swift Enterprises, on the outskirts of Shopton. At this vast, foursquare-mile experimental station, Tom and his distinguished scientist father, Tom Sr., Developed their amazing inventions.

"Do you suppose those UFO's are really from outer space?" Phyl asked excitedly.

Tom shrugged. "It's possible."

"Maybe it's a kookie idea," Bud put in, "but I'm wondering if they have anything to do with that wild rumor we heard today."

"What rumor?" Sandy queried.

The weird sky objects wheeled overhead like colored meteors Tom explained that the Swifts' overseas tele-caster had reported that a fantastic story was circulating among European scientists. The story hinted that an unnamed foreign space power was working on a spectacular comet project-something that would startle the world.

"A comet project!" Sandy's eyes widened. "Like the comet probe you're planning, Tom?"

"Could be, I guess. But the rumor sounded as if it were something a lot more dramatic."

"Jeepers, I hope the Brungarians aren't behind it!" Sandy said worriedly.

"So do I," Tom agreed. The same disturbing thought had already crossed his mind. More than once, spacemen from the dictator-ruled country of Brungaria had done their best to harass and thwart Swift space expeditions, both to the phantom satellite Nestria and the moon.

Tom switched on the convertible's short-wave radio and contacted Enterprises. To his surprise, the plant operator knew nothing about the yacht-club call.

"That's odd," Tom muttered aloud with a puzzled frown as he turned off the set. "Stop to think of it, though, the plant would have called me over my pocket pencil radio."

"Then who did call you?" Bud asked.

"Don't know. May have been Dad or Harlan Ames." Ames was the chief of Swift Enterprises' security staff.

Presently the high walls of the research station loomed ahead through the darkness. The guard at the entrance snapped a friendly salute and the massive, electronic-controlled gate swung open to admit the convertible.

Inside lay a sprawling complex of modern laboratories, workshops, and hangars. Slender steel radio masts rose against the night sky, topped by red aircraft obstruction lights.

Bud sped through the plant grounds, crisscrossed by ghostly white runways, and parked near the Main Building. The observatory dome at the top was open with the latticed, tubular antenna of the space prober poking out of the viewing slit.

Tom noticed a gleam of light from the office which he shared with his father. "I'll bet that's Dad up there now," Tom said. "He must have been the one who called me. Bud, why don't you take the girls up to the dome and I'll meet you there after I check with him."

"Okay. Don't gab too long, genius boy."

A few moments later Tom stepped off the elevator and hurried to the Swifts' double office, leaving his dark-haired pal to ascend to the observatory with Sandy and Phyl.

The office door opened as Tom turned the knob, and the lights were on, but he was surprised to find no one inside. The huge, luxuriously furnished room had deep-pile carpeting, comfortable leather lounge chairs, a conference table, and broad twin desks for father and son at opposite ends. Arranged about the office were models in metal and plastic of the Swifts' inventions.

"Maybe Dad's up in the dome, too," Tom thought. "I'll see if he left a note on my desk."

As he strode across the room, the lights suddenly went out! Tom froze to a halt. Was someone else in the office, or had the lights failed accidentally?

There was a strange glow from the top of his desk. Tom walked cautiously toward it, then gasped at what he saw. In glowing yellow fluorescent paint on his black-leather desk blotter was a crude drawing of a comet with the warning: DOOM TO TOM SWIFT!

The young inventor heard a slight noise behind him as he bent over the desk. He stiffened with a sudden sense of danger.

As he straightened up and whirled around, a hard blow caught him on the side of the head. Tom sank to the carpet with a groan!

CHAPTER II

THE FLYING GOAT

WHEN the elevator reached the observatory dome, Bud and the girls saw a tall man standing at the console of the space prober.

"Hi, Dad!" Sandy hugged her father. "We thought you were down in your office."

Mr. Swift turned in surprise as he switched off the megascope. Trimly built, with close-cropped graying hair, he looked like a slightly older Tom Jr. "Well! This is an unexpected pleasure!" Returning Sandy's hug, he smiled at Phyl and Bud. "What brings you youngsters up here at this time of night?"

Excitedly the three told about the UFO's.

"Are they still visible?" Mr. Swift asked.

"We hope so," Phyl said. "We could still see a flare of light in the sky from the direction of the lake." Sandy added, "From up here, the view should be perfect!"

Mr. Swift eagerly tuned the prober circuitry and rotated the dome to train the antenna toward Lake Carlopa. But the prober viewing screen showed only the night sky, with no trace of the dazzling colored disks.

"They're gone!" Sandy wailed in disappointment. "We're too late!"

Mr. Swift called the regional Air Traffic Control facility, and asked if they had had radar contact with the strange objects. The chief controller told him that nothing had appeared on their scopes other than normal traffic.

"Tough luck." Bud grimaced. "Speaking of being late, I wonder what's keeping Tom." He strode to a wall phone and rang the Swifts' office. No one answered. "Must be on his way up."

But after ten minutes Tom still had not appeared. Nor was there any response when Bud had him paged on the public-address system. Mr. Swift did not know who had called Tom at the yacht club.

Phyl giggled. "Maybe he's dozing off after all the excitement."

"More likely he has his nose buried in some book on fifth-dimensional astro-whizzics," Bud joked. "We may have to drag him out bodily."

Mr. Swift closed the observatory for the night, and all four went down to the office. They found the door unlocked but the office dark.

"It's not like Tom to go off without locking up." Mr. Swift frowned and called, "Anyone in here?" He switched on the lights to make sure.

Both Sandy and Phyl cried out in alarm. Tom lay sprawled unconscious near his desk!

They rushed toward him. As Mr. Swift examined his son, Tom's eyes flickered and Sandy hurried to bring spirits of ammonia from the first-aid cabinet. Presently Tom revived enough to tell what had happened.

Grim-faced, Mr. Swift said, "Switch on the patrol scope, Bud, while I call Security!"

Any intruder not wearing a special electronic wrist amulet designed to trap the radar impulses would show up as a blip on the various scopes installed about the research station. But Bud reported there was no indication on the screen.

"Wouldn't there be an automatic alarm if someone broke into the grounds?" Sandy asked.

"Only in the security office." Bud explained that the plant-wide alarm system had been disconnected recently to keep from warning any intruder that his presence had been detected.

Phil Radnor, Ames's blond, barrel-chested assistant, soon arrived with two security guards. "Whoever did it must be an employee," he declared.

Tom exchanged a worried glance with his father. "That's hard to believe, Rad."

"It's the only answer-unless one of the amulets has been stolen." Picking up the telephone, Radnor issued orders that a thorough search of the grounds and buildings be made.

Mr. Swift insisted on taking Tom to the Enterprises infirmary. Doc Simpson, the young plant medic, found no sign of serious injury.

Next morning at home Tom and his father talked over the night's events while Mrs. Swift, a slim, pretty woman, served breakfast.

"Those UFO's were really spectacular, Dad!" Tom said. "What's your opinion about them?"

"The whole thing seems fantastic, but we'll have to reserve judgment," Mr. Swift replied. "By the way, I've some news that may interest you, son. Last night I sighted a new comet."

"That's great!" Tom exclaimed. Since these heavenly bodies that sweep around the sun with glowing tails are named after their discoverers, he added, "Congratulations on Comet Swift!"

Mr. Swift smiled. "It's not official yet. I notified the Harvard Observatory, but of course it'll be a while before other observatories can confirm the sighting with ordinary telescopes."

Tom's eyes blazed with eager interest. "Do you think the comet may be suitable for my probe?" Recently the government had commissioned the famous young astronaut to carry out a scientific space probe of the next comet to pass near earth. Tom even hoped for a manned landing.

Mr. Swift replied, "My guess would be no, but it's hard to say until I've enough data to plot its orbit." Glancing at his watch, he switched on the TV set. "Wonder if there'll be any word on that rumored foreign comet project."

The morning news show came on the screen. The newscaster told about the weird colored disks seen over Lake Carlopa, then went on: "An even more startling story comes from overseas. Reliable sources report that Brungaria is planning to create a spectacular man-made comet! An official spokesman would not confirm the report, but he did say that if such a comet were launched, any probe of it by another country would be considered an unfriendly act."

Tom gasped. "Was that crack aimed at us?"

"Hmm." Mr. Swift's face wore a worried frown. "As far as I know, we're the only ones who are planning a comet probe - and Brungaria would certainly enjoy making trouble for the United States."

Mrs. Swift murmured, "Goodness, I hope not."

Tom patted her hand and grinned. "Don't worry, Mom - it's probably more of their phony propaganda. Anyhow, they can't put a 'Keep Off' sign on natural comets."

Nevertheless, both Tom and his father were concerned. As they drove to the plant, Mr. Swift mused aloud, "If the Brungarians have the scientific capability, there's no doubt that launching an artificial comet would be a valuable space experiment."

Tom commented, "Also a great publicity gimmick to show the world what space hotshots they are." He was silent for a moment. "Dad, you don't suppose that 'Doom' sign was a warning from the Brungarians?"

"I'm wondering the same thing," Mr. Swift confessed worriedly. "If so, it means that an enemy agent has access to Enterprises."

When their car pulled into the experimental station, an excited knot of employees were gathered around the Main Building.

Tom slid out from behind the wheel. "What's going on, Sam?" He asked a lab technician.

"Take a look up there-on top of the dome!"

Both Swifts gave astonished gasps. A bearded Rocky Mountain goat was perched atop the shuttered slit of the observatory!

"Great Scott!" Mr. Swift exclaimed. "Who's responsible for this?"

"Don't know, sir," Sam Crivet replied. "Someone just spotted him a few minutes ago."

A jeep driven by a plant guard came speeding to the scene. Harlan Ames, the security chief, jumped out, his face red with anger. Mr. Swift inquired, "Any idea how this happened, Harlan?"

"None. I just now got a call from the control-tower operator. But I'll soon get to the bottom of this!" Ames vowed.

Tom's lips twitched as he tried hard not to smile. "The goat must have come from the bionics lab," he said to the security chief.

"The question is, Who put it up there?" Ames fumed. He snapped an order to the guard to bring a repelatron sled.

Tom had invented these small, handy vehicles, often called "flying carpets," for moon transport work. They were sturdy metal platforms powered by a repelatron - another of Tom's inventions - which generated a repulsion beam to loft them from the ground.

While Tom was waiting for the repelatron sled, Bud arrived in his convertible. "Come on, fly-boy!" Tom called. "Help me rescue this airborne goat!"

As soon as the guard brought the flying carpet, the two youths soared to the top of the dome. The whiskered mountain goat proved stubborn at first. When Bud rashly tried to tug it by the horns, he almost got butted off the sled. But finally the boys succeeded in ferrying the animal back to the ground, amid loud cheers from the crowd of grinning spectators.

"Wow!" Bud wiped his forehead in relief. "For a second, he almost had me airborne!"

He accompanied the Swifts to their office. A wire-service news reporter soon called to ask about Tom's reaction to the Brungarian comet story.

"Interesting idea, if it's true," Tom told him. "Since the Brungarian Government isn't willing to give a straight Yes or No to the story, I'd rather not comment just yet."

He had barely hung up when the telephone jangled again. This time Dan Perkins of the Shopton Evening Bulletin was on the line. "What's this I hear about a flying goat at Enterprises?" The editor needled.

"Haven't seen any lately with wings, but I'll keep a lookout," Tom quipped.

As he finished talking, Ames came into the office. Tom related the conversation and added, "Someone tipped him off anonymously."

Ames snorted. "Big joke! Perkins will spread that yarn all over the front page!"

The telephone rang. "Good grief! Not another one?" Bud said as Tom picked up the receiver.

The caller spoke in a shrill, squeaky voice. "Give me back my captured crewmate, you nasty earthling!" He demanded.

Tom grinned good-naturedly. "Okay, I'll bite. What does this crewmate of yours look like?"

"Two horns and whiskers, like all us Martians!" The caller replied. Then he bleated, "Ba-a-a!"

Hearing the receiver click, Tom hung up too. "The news seems to be getting around," he said mildly after describing the call.

Ames was furious over the goat prank, and baffled as to who might be responsible. Nor had he any clues to report on the incident of the night before. "We've checked and accounted for all the radar amulets," he told the Swifts. "None are missing."

Mr. Swift drummed his fingers thoughtfully on the desk. "Are we up against two intruders - or is the same person behind both incidents?"

"If it's the same person, that joker sure has a rough sense of humor," Tom said ruefully, fingering the sore spot on his head.

Bud spoke up. "Maybe the guy got into the plant grounds from some sort of aircraft!"

"Like a flying saucer, perhaps?" Tom joked.

"No - a copter, maybe," Bud countered.

Ames shook his head. "Not a chance. Radnor had the aircraft warning radar checked last night and it worked perfectly."

Bud gave up the mystery with a shrug. "Are we going to run that test on your telesampler, Tom?"

"Sure thing - this afternoon."

"Okay. I'll check out the Sky Queen and set everything up."

Soon after Bud left the office, Tom hopped on a jet scooter outside the building and sped to his glass-walled private laboratory to work on the instrumentation of his comet probe. But he found it hard to concentrate. His thoughts continued to stray back to the mysterious events of the past twenty-four hours.

At lunchtime Bud came dashing into the lab. His face wore a mischievous grin. "Get your telesampler bench rig ready, Tom!" he exclaimed. "Chow's coming!"

A few moments later the door swung open and a plump, cowboy-booted figure came clumping into the room, pushing a lunch cart in front of his ample midriff. Chow Winkler, a balding, sun-bronzed, chuck-wagon cook from Texas, was the Swifts' private chef.

"Soup's on, buckaroos!" He boomed. "An" looky here at this chocolate cake I jest baked!"

"Mmm, boy! Looks delicious!" Bud said. He reached one hand inside a curious-looking device on the laboratory workbench, then pulled out his fingers covered with chocolate frosting. "Tastes delicious, too!" Bud added, licking off the icing with loud lip smacks.

Chow blinked in surprise. He looked at the cake, then stared at Bud, goggle-eyed. "B-b-brand my beefsteak, what's goin' on here?"

Although Bud was ten feet from the lunch cart, a hunk had just been gouged out of the cake frosting!

CHAPTER III

GROUND LIGHTNING!

"DON'T panic, old-timer," Bud said soothingly. "I don't aim to eat it all up-just yet." He thrust his ringers into the device on the workbench again and licked off more icing.

Chow's jaw sagged and his double chin quivered in helpless astonishment. Before his very eyes the hole in the cake frosting was growing larger! "Quit funnin' me!" He bellowed, glaring at Bud. "I don't know how in tarnation you're doin' it, but you're up to some kind o' hocus-pocus!"

At Chow's ferocious expression, the boys gave way to howls of laughter.

Tom switched off the device. "Don't mind fly-boy, Chow. He's not really the one who's swipping your icing - it's my telesampler here."

"Your tele-whozis?"

"Telesampler, my newest invention. It's designed to obtain samples of any substance at a distance."

Chow stared at the complicated hookup of microcircuitry, enclosed in blocks of crystal plastic. Atop the assembly was a swivel-mounted dish antenna, from the center of which protruded an odd microwave radiator of ringed latticework, somewhat resembling a miniature version of Tom's space prober. A curving tube led from the antenna dish to a boxlike receptacle.

Chow walked closer, scowling, and pointed a ringer suspiciously at the antenna. "You mean this here thingumabob sucked the frosting right off the cake like a-like a vacuum cleaner?"

Tom grinned. "Well, not quite like a vacuum cleaner. But it did pull off the frosting. The device operates by an electromagnetic wave action. In principle at least, it can work at ranges of hundreds of thousands of miles."

"Hoppin' horned toads!" The cook blurted. "Then if I cooked up a mess o' frijole beans out in Texas, you could sample 'em right here in Shopton - is that what you're sayin?"

"I could if I had a clear line of sight and my telesampler generated enough power. This experimental lab setup couldn't do it, of course. Anyhow," Tom added with a chuckle, "I'd rather have you dishing up chuck at Enterprises, pard."

As the boys tackled the appetizing lunch of steak and French fried potatoes, Chow continued to peer at the telesampler. "How does she work, boss?"

"Well, the antenna pulses out a concentrated beam that knocks particles loose from the surface of the target substance," Tom explained between mouthfuls, "the same way a beam of light makes a photoelectric cell give off electrons."

"How d 'ye make them lil bitty party-cules o' the stuff come back to you?" Chow asked.

"They're in an ionized state, so the echo - or reflected beam-carries them back to the tele-sampler. And the tubing connected to the antenna dish is a wave guide that carries the particles to the recovery tank-which is the box Bud was scooping the icing from."

Chow shook his head admiringly. "Brand my burro, it's plumb wonderful! Why, a prospector could scoop gold out of a mountain ten miles away with this lil ole whatchamacallit!"

"Yes." Tom nodded. "Matter of fact, this afternoon Bud and I are going to test an airborne model of my telesampler that's specially designed for mineral prospecting. It won't just detect radioactive substances like my Damonscope does, or metals like Dad's metal detector - it will actually scoop up samples of anything I aim it at - or so I'm hoping."

"Will the beam pierce soil?" Bud asked.

"No. The airborne model has a laser to burn a hole down to any depth I want to sample - and my space model will have one, too." Tom added that they also would analyze and identify the sample automatically by a Swift mass spectrometer. "With my space model, I'm hoping to mineral-prospect distant asteroids and other celestial bodies. It'll be the heart of my comet probe."

"Wow! How about that, Chow?" Bud exclaimed. "Imagine bringing home a piece of comet!"

"Sure beats a pickax, like them ole desert-rat prospectors use." Chow plucked off his chef's hat. "Speakin' o' scientific wonders, how'd 'ye like my new head o' hair?"

On his glistening bald dome several strands of baby-like down had sprouted! "New brand o 'hair restorer I jes' tried did the trick."

"Hair? It looks like peach fuzz," Bud teased.

"Don't let him kid you, Chow," Tom said hastily. "Keep it up and you may grow a real crop!"

Chow gave Bud a glare and bent his head so the boys could inspect and feel the hair. After both had duly admired it, the chef waddled out, preening the fuzz proudly with his fingertips.

As soon as they finished eating, the two boys jeeped out to the airfield. The Sky Queen had already been raised from its special underground hangar. This giant, three-decker aircraft, atomic-powered and equipped with jet lifters, was often called Tom's Flying Lab.

Several employees and mechanics were standing by. Hank Sterling, the blond, square-jawed chief engineer of Enterprises, and Arvid Hanson, a hulking master craftsman who helped build the prototypes of the Swifts' inventions, hailed Tom as he climbed out of the jeep.

"Ready for take-off, skipper?" The former asked.

"Sure thing, Hank!"

"We had some trouble with the telesampler mounting," Arv reported, "but she's all set now."

Marc Bolen, a dark-browed young astrophysicist who was working on the instrumentation for Tom's comet probe, came strolling up. "Where's your telesampler installed, Tom?" He inquired.

"In that blister just under the nose. Can't see much of it now, but when the prospecting run gets underway, a gun unit will extend out, containing the microwave radiator and the laser."

The two boys climbed aboard. Tom took his place at the controls, with Bud as copilot. After they had completed the pre-flight check list, the tower radioed clearance for take-off. With a roar of its jet lifters the Sky Queen soared vertically into the blue.

At a thousand feet Tom leveled off and turned to a westerly heading. He eased down to a lower altitude as they came to a barren, hilly area chosen for the test. "Okay, take over, Bud. Keep her hovering here until I tell you to move on to another spot."

"Roger!"

Tom climbed down into the blister and wriggled into a small bucket seat facing the tele-sampler console. A low hum came from the machine as he switched on power. Tom flicked a lever. Through the window of the blister, he saw the flaring tube of the gun unit move out into position. He aimed it at a bare patch of soil below and tuned the circuits.

A light flashed as the analysis of the target substance appeared on the readout panel. With a grin, Tom opened a small hatch on the recovery tank and scooped out a reddish-brown substance.

"How we doing?" Bud called over the intercom.

"Great. Just dredged up some aluminum silicate-clay to you. Let's try that next hill."

The Sky Queen moved ahead. Again Tom aimed and tuned the telesampler gun. He frowned in surprise at the indication on the readout panel. Before he could open the recovery tank, a blinding flash arced upward from the ground. Tom gasped. The console lights had gone dark and an acrid odor of burned insulation came from the machine. He spoke into the intercom: "Bud! . . . Bud, can you read me?"

No answer. Tom sprang from his seat and scrambled up the ladder to the flight compartment. Bud greeted him with a startled look.

"What in aerospace happened, skipper?"

"Don't know," Tom replied, "but I have a horrible hunch I just struck an underground power line! How are the instruments?"

"Dead. So's the radio and intercom."

Tom made a wry face. "Great! The laser must have cut into a buried conduit, and the tele-sampler beam nibbled the rest of the way through the insulation to the cable itself."

Bud asked, "But what caused the flash? Wouldn't the power short to the ground?"

"Normally yes, but some of the current must have surged up the path of the ionized particles in the beam, like a lightning discharge." Tom frowned and ran his fingers through his blond crew cut. "Anyhow, that's my guess. The tele-sampler's microwave action is so complicated, it's hard to tell exactly."

Both the Queen's regular power supply and the automatic stand-by system had been knocked out by the sudden overload. Tom piloted the plane back to Enterprises without benefit of the electrical servocontrols. Unable to radio the tower, he circled the field and waggled the Queen's wings until he got a green light to land.

Hank Sterling and the others, who had been waiting in the underground hangar for Tom's radio report, came rushing out on the field. They listened in dismay to his story.

"What a break!" Hank said. "If I'm not mistaken, that's the power line to Greenville." He made a hasty telephone call in the hangar, then reported to Tom, "You blacked out the town!"

The young inventor groaned. "Boy, this just isn't my day! Hank, fly a repair crew over there in a copter, and do what you can do to help repair the break."

"Wilco, skipper!"

Tom called both the Mayor of Greenville and the power company to apologize, and promised that Swift Enterprises would pay for any damages. Then, with the help of Arv and Bud, he removed his damaged telesampler from the Queen and trucked it to his laboratory.

"This sure is tough luck," Bud sympathized. "Will it set you back much?"

Tom shrugged. "I hope not. At least there's one bright spot - the telesampler seemed to work fine on that first sample we took."

The telephone rang shrilly. He scooped it up. "Tom Swift Jr. Here."

A strange voice said, "Have you had enough, Swift? Are you ready to beg for mercy?"

"Who is this?" Tom demanded angrily.

"Never mind who I am. Just stand by for more trouble because I intend to ruin you Swifts! Before I'm done, Swift Enterprises will be the laughingstock of the scientific world!"

There was a peal of maniacal laughter - then a loud click as the caller hung up!

CHAPTER IV

VANISHING FUZZ

TOM put down the telephone slowly - the jeering laugh still ringing in his ears.

Seeing the stunned look on his friend's face, Bud asked, "What's wrong, Tom? Who was it?"

The young inventor related the threatening call. Both Arv and Bud were shocked.

"Maybe it was that same joker who made the billy-goat call this morning," Bud suggested.

Tom rubbed his jaw worriedly. "Could be. But this one sure didn't sound like any gag."

Arv put in, "You're sure there was no sabotage involved in the test accident?"

"I don't see how," Tom said, shaking his head. "Nobody could've arranged for the beam to hit that power line. My guess is whoever called was just trying to throw a scare into me - but I still don't like it."

Picking up the telephone again, Tom dialed the security department and reported the call to Harlan Ames. He, too, was disturbed by the threats.

"Sounds like a lunatic to me - but there's no chance of tracing the call now." Ames was silent a moment, then asked, "How many people know about the power-line accident?"

"Quite a few in Greenville," Tom said wryly.

"Okay. We'll start checking there."

Still uneasy, Tom went to the Main Building to see his father, leaving Arv and Bud to begin disassembling the telesampler for repairs.

Mr. Swift listened to the news gravely. "Hard to imagine who it might be," he mused, frowning. "Perhaps some enemy agent."

"You know of no one who might have that strong a grudge against us, Dad?"

Mr. Swift shook his head. "Jealousies do arise among scientists, but I certainly can't think of anybody who'd want to ruin us." He shrugged. "Well, no sense losing sleep over it. Something else has come up, Tom."

He picked up a telegram from his desk and handed it to his son.

The message, signed by a government official, requested the Swifts to attend an urgent meeting in Washington, D. C., At 10 a. M. Wednesday, the next morning.

"I wonder if it's about the comet probe," Tom said anxiously.

"Very likely, but we'll have to wait and see."

Next day the two inventors took off from the Enterprises airfield in a sleek, Swift-designed executive jet. Tom Sr., An expert airman who had taught his son to fly, piloted the craft to the Washington airport.

Soon after they landed, they joined military men, space officials, and a State Department representative in a conference room at the Pentagon.

Mungo Drake, the space agency director, began, "This meeting was called for two reasons - first, to consider the rumored Brungarian comet project." He explained that the Brungarian warning about an "unfriendly act" might make it necessary to cancel the American comet probe.

The State Department official agreed, saying, "We certainly must avoid any risk of an incident in the present state of world tension."

Tom spoke up. "You mean a clash over a man-made comet of another country, sir? But what's to keep us from probing a natural comet?"

"The problem is," Drake said, "how to tell the difference."

Both Swifts thought this would be easy but the others disagreed. One of the space agency men pointed out that the Brungarians' cloak of secrecy and mystery around their project meant that even the wildest possibilities had to be considered.

"For all we know," he argued, "they may have devised a way to attract comets or control their courses. If we intruded on one they had captured, it would give them a perfect excuse to interfere with our satellites and space probes."

There were murmurs of agreement. Another official said, "The Brungarians are clever, the way they've handled this situation. We don't even know if it is an artificial comet they're working on. By not confirming or denying the rumor, they've tied our hands."

"Why should we let them?" Tom objected. "I'm convinced they have less space know - how than we do. Their silence could mean the whole rumor is phony - a trick to block our American comet research."

It could also be a trick to maneuver us into trouble, "the State Department representative warned." If we blunder into any Brungarian real estate in outer space, we can be branded as aggressors."

The Swifts argued keenly against yielding to a possible Brungarian bluff. Some men at the meeting were swayed by the two famous inventors. After further discussion, a final decision was put off and Tom was told to continue work on the project for the time being.

Then Mungo Drake spoke up. "Now we come to the problem of those mysterious unidentified flying objects-which some of you may still think are nonsense. What do you Swifts think about them?"

"I'll let my son answer that," Mr. Swift said.

Tom grinned. "I have good reason for believing in them - I saw a UFO display Monday night."

"Good." Drake nodded. "Then it will come as no surprise to you that the Defense Department is becoming concerned about these queer craft."

He turned the meeting over to Air Force General Hagan. The general reported that American air bases had verified a number of UFO sightings. Tactical aircraft had been sent in pursuit of the colored disks, only to see them whiz out of range at tremendous speeds and then disappear.

"But the most peculiar fact about the UFO's," General Hagan said, "is that they cannot be detected on radar-even when in clear view."

Mr. Swift was startled. "Perhaps that's why I couldn't pick them up on the megascope!"

A Defense Department scientist suggested that the craft might have some means of blinding radar. "The only other answer," he added, "is that the UFO's aren't real-just a mass hallucination."

Tom expressed the opinion that this was unlikely. Before the meeting ended, he promised to ask his space friends about the strange colored disks.

Months before, a black missile from outer space had landed at Swift Enterprises. It was etched with curious mathematical symbols. Tom and his father had decoded the symbols and later had made radio contact with the senders - creatures living elsewhere in our solar system. The radio signals were modulated to show up on an oscilloscope screen in the visual pattern of the code symbols.

After lunch the Swifts flew back to Enterprises. They went at once to the space communications laboratory. Here Tom beamed out a message over a powerful transmitter. Minutes passed as they waited for a reply from the friendly space creatures.

At last a bell rang, indicating that radio signals were being picked up and decoded by the electronic brain which Tom had devised to process the messages automatically. Curious patterns of light appeared and faded on the machine's oscilloscope screen. The translated output was reeled off on tape: we are most interested to learn of strange objects appearing in earth's skies. We do not know if they are spacecraft but will keep watch for them.

"They're as puzzled as we are," Mr. Swift said.

"If the UFO's are spacecraft, it's odd they haven't spotted them already," Tom commented.

Still pondering the mystery, the young inventor went to his laboratory to begin repairing his airborne telesampler. Bud soon joined him. In mid-afternoon, the door of the lab swung open and Chow Winkler wheeled in his cart.

"Jest a HI afternoon snack, amigos. Somethin' fer your stummicks while you rest your brains."

Tom smiled. "Chow, you're the greatest."

As the boys helped themselves from a pot of cocoa on the cart, the stout cook began telling about the wonderful snake-oil hair restorer he had been using. "Friend in Texas makes it," Chow said, proudly displaying his fuzz again.

Bud took a long gulp of the cocoa, then exploded into loud, sputtering gasps! Tom, too, was making violent strangling noises.

"R-r-roarin" rockets! "Bud yelled." What did you put into this stuff?"

Chow stared in surprise. "It's jest cocoa."

"Tell us another!" Bud stormed, his eyes watering. "This could fry your tonsils!"

"It's laced with tabasco sauce!" Tom gasped.

Bud went for water from the workbench faucet. "What a sneaky trick! Just to get back for that icing gag!" He ignored Chow's loud, repeated protests of innocence.

"Honest Injun, I didn't put nothin' in it!"

Chow persisted, bending his head to sniff the cocoa. Suddenly Tom noticed the chef's shiny pate. It was as bald as ever!

"Hey!" Tom exclaimed. "What happened to your new baby hair?"

Chow felt his ivory-smooth dome and let out a wail. "It's gone! The fuzz is gone!"

Bud ran to the door. "Look in the telesampler tank!" He yelled back with a wicked grin.

Chow gaped at the experimental rig which the boys had used to filch his cake frosting. His face went red with rage. "You low-down sidewinder!" The cook roared. "Rustle my fuzz, will you? I'll massa-cree you fer this!" He bounded out the doorway in pursuit of Bud.

Tom-still half-choking, but now with laughter - was about to go after them when the telephone rang.

The guard was calling from the main gate. "There's a nice little old lady here to see you, Tom. Says her name is Mrs. Abernathy."

"What does she want?" The young inventor asked.

"Won't tell me-just that she has some vitally important information to give you."

Tom hesitated, fearing the woman might be a crank. But he hated to be impolite. "Okay, Mike, send her up."

A few minutes later a jeep drew up outside with a small, bespectacled, gray-haired woman seated beside the guard who was driving.

Tom greeted her as she entered the laboratory. "Please sit down, Mrs. Abernathy. What was it you wanted to see me about?"

The woman took a chair, then bent forward eagerly. "I know the secret of those UFO's!"

CHAPTER V

A WHITE-FACED CAPTIVE

MRS. Abernathy's startling announcement about the UFO's caught Tom by surprise. Before he could say anything, a buzzer sounded in the lab.

Tom's eyes swung hastily to a wall panel. A red light was flashing - the private warning from Security that an intruder had been detected in the plant!

"Excuse me," Tom murmured to his visitor. He got up and switched on the patrol scope.

A sweeping finger of light painted a small blip on the screen. The young inventor gasped as he noted its position. The intruder was right in Tom's own laboratory building!

Then a thought struck him. "Mrs. Abernathy, were you given a radar amulet at the gate?"

"Why-why, yes, of course," she said with a somewhat bewildered look. "Is anything wrong?"

Tom gave the elderly woman a reassuring smile. "There seems to be a bit of trouble, but nothing for you to worry about," he replied.

Tom telephoned the security department. "What's the word on that radar alarm?" He asked the operator on duty.

"The blip just triggered our main scope a couple of minutes ago," the operator reported. "We can't figure how the intruder got in without being detected sooner. Mr. Ames is rushing over to your lab right now with a security squad."

"Right! Here they are!" Tom said, glancing out the window. Two jeeps had just screeched to a halt.

Harlan Ames leaped from one car and barked orders to his men. Several of the guards fanned out to cover all exits. Then Ames strode into the building with the others. Tom met him at the doorway of the laboratory.

The security chief asked, "All clear in your lab, Tom?"

The young inventor nodded. "I have a visitor but she's wearing an amulet."

"Good enough." Ames turned to his men. "We'll work upward, floor by floor. Search all rooms-check every possible hiding place! Mac, you watch the corridor. Peters, you cover the fire stairs!"

Tom himself was eager to join in the search. Mrs. Abernathy had overheard what was said and seemed upset by the sudden turn of events. Tom explained the situation to her and added apologetically, "Would you mind going to my office and waiting for me there?"

"No, of course not," she said.

Tom rang for a laboratory attendant and asked him to drive his visitor to the Main Building. As the pair left, Tom thought, "Maybe I'd better check the lab - and the living quarters next door! If the intruder has a way of ducking radar, he may have sneaked in hours ago-before I even got back from Washington!"

Tom strode toward a storage closet in the laboratory, intending to look inside. As he passed the patrol scope, he stopped short.

The blip had disappeared from the screen!

With a gasp, the young inventor dashed back to the corridor and called to Ames. The security chief came on the run. When Tom told him what had happened, he too was baffled.

"The fellow couldn't have escaped!" Ames declared. "Not with all the exits guarded!"

Suddenly Tom's eyes widened. He snapped his fingers. "Harlan, I wonder if that blip was caused by my visitor!"

"You said she had an amulet," Ames objected.

"Sure, but maybe it's not working. As long as she's sitting in a jeep right next to the driver, his amulet shields both of them from the radar impulses. That's why she wasn't detected until she came into the lab."

Tom pointed to the patrol scope. "If I'm right, she'll show up again as soon as the driver lets her off at the Main Building."

The two watched the screen. Soon the point of light reappeared - this time at the position of the Main Building!

"Your hunch panned out!" Ames declared. "We'd better go and check on her amulet." The security chief called a halt to the search, but left the guards posted at the exits as a precaution. Then he and Tom jeeped to the Main Building.

Mrs. Abernathy, seated in a comfortable chair outside the Swifts' office, was chatting with their secretary, Miss Trent.

"Please excuse all this nuisance," Tom apologized to his elderly visitor. "May we see that radar amulet you were given?"

"Of course." Mrs. Abernathy reached inside her coat sleeve and unsnapped the amulet bracelet.

The device consisted of a pink plastic pod attached to a beaded chain. Tom's eyes narrowed. "This isn't even genuine, Harlan!" He blurted.

"You mean she was given a fake?" Ames gasped.

"Sure - it's just a copy." Tom held the pod up against the light. "See? It doesn't even have any electronic components inside!"

Ames stared in amazement. "Then someone must have slipped this fake into the supply of amulets at the gatehouse!"

"Right. And unless it was done in the last day or two, a real amulet must be missing!"

"How do you know that?" Ames questioned.

"Because you and Rad had all the amulets counted after what happened Monday night," Tom reminded him. "If a real one weren't missing, the count would have revealed one too many."

Ames pounded his fist into his palm. "So that explains what's been going on around here! There is an intruder in the plant - and the reason he hasn't been detected on radar is that he's armed with the missing amulet!"

Tom nodded as he paced the floor. "I'll bet the switch of amulets was made during one of our escorted public tours-like on the Fourth of July. Whoever did it got a genuine amulet at the gate, then turned in a fake when he left."

"That still wouldn't explain how he slipped back in, later," Ames countered.

Tom stopped abruptly. A strange look came over his face. "Harlan, I'll bet I know who's behind all this!" He exclaimed, picking up the telephone on Miss Trent's desk. "This call will tell us whether I'm right or wrong."

Meanwhile, Chow and Bud, as well as many employees in the laboratory building, were unaware of the radar alarm. Puffing hard, Chow chased Bud vainly up and down several floors and finally gave up in disgust.

Still disgruntled over the loss of his newly grown hair, the roly-poly cook waddled back to his galley. A faint noise from the pantry off the kitchen caught his attention.

Chow peered inside. He stiffened as his keen eyes saw the toe of a loafer-shod foot protruding from behind a stack of food cartons. Someone was kneeling behind the stack!

The plump Texan chuckled to himself. "So that's where you're hidin', Buddy boy! Up to more tricks, eh? Wai, we'll see about that!"

Chow gave a gusty yawn. "Reckon I'll knock off fer the day!" He said aloud. Shucking his apron, he donned his cowboy hat, switched off the lights, and clumped loudly toward the doorway in his high-heeled boots. He slammed the door, but instead of going out, waited in the dark silently as an Indian. Seconds passed.

Then Chow heard more noises. Flattened to the wall, he could sense a shadowy figure groping its way out of the pantry into the kitchen.

Chow sprang into action like a panther! He snatched an open canister of flour from the counter and hurled it over the figure's head, aiming by sound and instinct. A stifled, choking yell told him he had scored a bull's-eye!

With a howl of glee, Chow reached out and flicked the light switch. His victim, coughing and spluttering, was just wrenching the canister off his head.

A second later Chow's expression froze. The victim's face was too plastered with flour to be recognizable - but he certainly was not Bud!

"Brand my biscuits, who are you?" The cook demanded.

Instead of answering, the white-faced figure made a dash for the door! But Chow, for all his bulk, could move like lightning. He thrust out one boot and the intruder tripped and went sprawling on the floor!

In a twinkling Chow snatched a length of cord from a drawer and hog-tied his captive like a helpless calf waiting to be branded. Then he called Tom on the intercom.

In a few minutes the young inventor came hurrying into the galley with Ames and Bud. Chow gestured to his prisoner, who was now propped on a stool. "Don't know who he is, boss, but I reckon I've jest roped the owl-hoot what's been causin' all the foofaraw around here!"

Tom grinned at sight of the captive's white mask-like face. "Okay, Chow. Good work, but you can untie him now. He's an acquaintance of mine."

CHAPTER VI

THE HAWK CLUE

"AN acquaintance o 'yours?" Chow echoed, staring first at Tom and then at the prisoner. "How kin you tell with all that gunk on his face?"

"Just a hunch," Tom said. "When we wipe it off, I think we'll find a joker named Ranee Gorman under all that flour."

While Chow untied the cords, Bud got a towel and swabbed off the flour. The husky copilot hooted with laughter as a freckled face, now fiery red with chagrin, became visible.

As Tom had suspected, the captive was Ranee Gorman, the high school prankster who had needled him at the Shop ton Yacht Club!

"What's the idea of powdering your face all up?" Bud teased. "Don't you know it's not becoming? Next thing, you'll be using lipstick!"

Tom explained that he had guessed Ranee was the mysterious intruder after recalling that a high school group had toured the plant on the Fourth of July. This had given Ranee an opportunity to filch a radar amulet, after coming prepared with a fake to turn in at the gate.

The loudspeaker call at the yacht club, Tom had deduced, was also arranged by Ranee. The youth had then taken the keys from the ignition of Bud's convertible, and had used them to open the car's trunk so that he could hide inside with the lid not completely closed. When Tom's group drove to Swift Enterprises in response to the P. A. Summons, Ranee was neatly transported into the plant without being seen.

"I tried calling the Germans and then phoned one of their neighbors," Tom concluded. "The neighbor told me that Mr. And Mrs. Gorman had left town on vacation - and that Ranee hadn't been seen at the house since Monday."

Ranee sheepishly admitted that Tom's deductions were correct. The freckled youth tried to put up a bold front, but he gulped and quailed as Harlan Ames stepped forward and grabbed him by the shirt. The enraged look on the security chief's face showed he was in no mood for trifling.

"Look, you smart aleck!" Ames snapped in blistering tones. "Do you have any idea how much trouble you've caused around here? We could turn you over to the FBI for violating plant security!"

"It was j-j-just a joke," Ranee quavered.

"Oh sure. Great sense of humor," Bud put in sarcastically. "Like conking Tom unconscious Monday night - that was really a swell gag!"

"What?" Ranee looked genuinely horrified. "I never did anything like that-honest!"

"No? And I suppose you never left that 'Doom' sign on his desk blotter, either!" Ames pursued.

Ranee shook his head fearfully. "I don't even know what you're talking about, sir!"

"But you did hoist the goat up on the dome?" Tom queried.

Ranee gulped and nodded. "I did it Monday night with one of your flying carpets."

"And the next morning you telephoned a news tip to the Bulletin and razzed me over the phone about your missing Martian crewmate?"

Again Ranee nodded. "I made the calls from a pay booth in the employees' lounge."

Tom went on, grinning, "And you also spiked our cocoa with tabasco sauce today?"

As the freckled teenager confessed to the prank, Bud flashed Chow a look of apology.

"Let's get down to the really important stuff," Ames growled. "What about that call after Tom shorted out the power line yesterday? I mean the call threatening to ruin the Swifts - and you laughing like a maniac just before you hung up."

"Not me, sir!" Ranee declared fervently. "I phoned about the goat - that's all!"

Under Ames's gimlet-eyed glare, the youth began to tremble. Beads of perspiration oozed from his forehead.

"Maybe you're telling the truth and maybe you aren't," the security chief rasped. "You're still the most likely suspect for what happened Monday night. I think we'd better turn you over to the police for questioning."

"Forget it, Harlan," Tom said. "I'm sure Ranee is telling the truth. He couldn't have got out of the car trunk and up to the office in time to paint that sign and knock me out."

Ranee gulped with relief. "Thanks, Tom - thanks a lot! I sure won't forget this!"

"You're letting him off scot-free after all the trouble he's caused us?" Ames asked Tom.

"I'm not saying he doesn't rate a good kick in the pants," Tom replied, "but there's no use our acting like soreheads over a practical joke. What really bothers me is letting all that ability go to waste. You'll have to admit, it took clever planning and nerve to pull such a stunt."

"You're sure being a sport about it," Ranee mumbled, red-faced.

Tom regarded him with a thoughtful frown. "If you'd cut the monkey business, Ranee, Enterprises could use a fellow like you. How'd you like a summer job here as lab assistant?"

Ranee brightened eagerly. "You mean that?"

"I do if you'll shape up - and stay shaped."

"Just try me!"

"Okay." Tom turned to Bud. "Take Ranee to Personnel and have him signed up. Say that I want him assigned to Jonas Cord's department."

"Wilco!" Bud winked at Tom, knowing Cord was one of the hardest taskmasters at Enterprises.

As the two went off, Ames frowned doubtfully. "I hope you're not making a mistake about that fellow, skipper."

Chow spoke up. "Purty all-fired generous o 'Tom, I'd call it."

"And pretty sharp-eyed of you to nab him, pardner," the young inventor responded. His face turned serious as he added, "Only trouble is we still haven't caught the real spook - the one who zapped me."

Tom went thoughtfully back to the Main Building. He found Mrs. Abernathy deep in conversation with his father, who had just flown back from a hasty two-hour inspection trip to the Swifts' rocket base on Fearing Island, off the Atlantic coast.

"Sorry for all the interruptions," Tom said to his visitor.

"Mrs. Abernathy has been telling me about the research work on which she assisted her husband," Mr. Swift remarked. "Up to the time of his death, Dr. Abernathy was a top clinical psychologist. I've read a fine textbook that he wrote."

Tom's eyebrows lifted in surprise. So Mrs. Abernathy was not just a sweet little old lady with wild ideas about flying saucers! "I'm eager to hear your theory about the UFO's," Tom said to her.

"First of all. I must tell you that I have seen them with my own eyes," the woman began.

"Indeed? Where?" Mr. Swift asked.

"While I was visiting an Indian settlement recently, in the Canadian north woods." Mrs. Abernathy explained that a forest fire had broken out around the village, and that the Indians were fighting the blaze when dazzling colored disks had suddenly appeared in the sky.

"Then a frightened bird flew by overhead," she went on. "It was a large hawk. Believe it or not, I saw the hawk fly directly through one of the disks!"

Tom and his father exchanged puzzled glances.

"Are you saying the UFO wasn't made of solid matter?" Tom asked.

"Since a bird could pass through it, I believe the disk was not real at all," Mrs. Abernathy replied. "In my opinion, the flying objects were imaginary-just a mass hallucination on the part of myself and the Indians."

The same theory expressed by the Defense Department scientist at the Washington meeting! Tom was startled.

"What would cause people to see such hallucinations?" He queried.

Mrs. Abernathy shrugged. "There are still many things we don't know about the human brain. But we do know that hypnotized persons can be made to see things which aren't real-also that persons in a keyed-up emotional state may have delusions. We were all very excited and worked up at the time of the forest fire. This may have caused us to imagine the UFO's."

She added that the Indians had heard wild stories and reports about the UFO's even before the forest fire. These might have planted the idea in their minds.

Mr. Swift nodded thoughtfully. "It's an interesting theory. What do you think, son?"

Tom frowned and rubbed his crew cut. "Frankly, I don't know what to think. It's true that when Bud and the girls and I saw the UFO's the other night, there had just been fireworks and everyone was pretty excited. That much would fit in with Mrs. Abernathy's theory."

After their visitor had left, Tom voiced some doubts. "Those disks travel awfully fast, Dad. With a forest fire going on, I think even a trained observer like her might be mistaken about what she saw - in any case, it's a long way from scientific proof."

"You have a point there," Mr. Swift agreed.

Tom told his father about the discovery of Ranee Gorman at the plant. Mr. Swift, who was able to see the amusing side of the situation, chuckled and approved o£ Tom's hiring the youth.

The elder scientist glanced at his watch. "After five, son. What say we surprise your mother by being on time for dinner for a change?"

Tom grinned. "Swell idea, Dad."

Just as they were about to leave, Miss Trent brought a letter into the office. "This just arrived by special delivery," she said.

The letter, postmarked Germany, was addressed to both Tom Sr. And Tom Jr. Mr. Swift opened the envelope. "It's from Karl Feng!" he said with a smile of pleasure.

Dr. Feng, an old acquaintance of the Swifts, was a professor of history of science at the University of Heidelberg.

The letter turned out to be a hastily scrawled note. Mr. Swift read it aloud. " 'My dear friends: I am coming to the United States soon and hope to visit you at Swift Enterprises. There is something I must tell you about, which I believe may be of great interest to you both. Sincerely, Karl Feng.'"

"Sounds important," Tom remarked. "I wonder what's on his mind."

"Hmm. So do I," said Mr. Swift. "He's enclosed something in the envelope."

"What is it, Dad?"

"Looks like a piece of old parchment-perhaps from an old manuscript." Frowning, Mr. Swift held out the fragment to his son.

It bore curious-looking symbols in faded ink!

CHAPTER VII

PURPLE DUST

TOM studied the strange markings on the parchment. "Dad, aren't these alchemical symbols?"

"You're right," Mr. Swift agreed. "Here's the sign for gold, or the sun, and this is the symbol for mercury - but I don't recognize some of these others. They look like Arabic script."

"Some of the great early alchemists were Arabs, weren't they?" Tom asked.

His father nodded. "Yes, indeed, although the science of alchemy - if it can be called a science - traces back to ancient Egypt."

Both Swifts knew that alchemy had flourished in Europe during the Middle Ages. Many of its students had spent their lives trying to make a substance called "the philosopher's stone" which could change base metals into gold. Even though some were frauds, their work helped to lay the foundations for modern chemistry.

"I wonder why Dr. Feng put this in with his note," Tom said. "Do you suppose it has something to do with whatever he wants to tell us?"

"Perhaps. But it's odd he didn't explain why he sent it." Thoughtfully Mr. Swift slipped the note and fragment back into the envelope. "Of course he teaches history of science, so maybe the piece got torn off an old manuscript and was sent along by accident."

Still mystified, the Swifts drove home.

At breakfast the next morning Tom switched on the TV news. "Maybe we'll hear something on the Brungarians' comet project," he said hopefully.

The newscaster began by telling how a Shopton boy had failed to return home, after hunting for rock specimens at a quarry. It was feared the young rockhound had suffered an accident. A search for the missing youth was being made.

"Goodness! I hope they find him," Mrs. Swift murmured anxiously.

Nothing was said about Brungaria's rumored artificial comet. But at the end of the show, the newscaster announced: "Here's something to interest you flying saucer fans. The UFO Study Club-which keeps tabs on those weird sky disks-will hold an open meeting Saturday night at Racklin Hall. The public is invited. The guest speaker will be Shopton's famous young inventor, Tom Swift Jr."

Tom looked at the others around the breakfast table in surprise.

"What's your topic going to be?" Sandy asked with a giggle. "Martian billy goats?"

Tom chuckled. "First I've heard of the whole thing. Must be a mistake - or a gag."

Nevertheless, Tom was rather annoyed by the unauthorized announcement. As soon as he got to the Swifts' office, Tom spoke to their secretary.

"Miss Trent, do you know anything about my being asked to speak at a UFO Study Club meeting this Saturday night?"

"UFO Study Club?" The brisk, efficient young woman puckered her brows, then said, "Oh, yes. A letter came yesterday with that name on it. I put it on your desk."

"Thanks. Guess I missed it." Tom added sheepishly, "Remind me to clean up that backlog of mail one of these days!"

He riffled through the pile of letters and found the one Miss Trent had mentioned. It turned out to be from Hubert Dubley, the head of the UFO group, inviting him to talk on extraterrestrial life at their next meeting.

Tom had barely finished reading the letter when the intercom buzzed. "Mr. Hubert Dubley is calling you," Miss Trent reported.

"Thanks." Tom picked up his telephone.

Dubley apologized for the premature publicity release. "It was a slip-up," he explained. "The club member who handles our public relations thought I'd already contacted you."

"That's all right," Tom said. "But I hope you can send out a correction, because I'm afraid I'll be too busy to attend the meeting."

"But, please! Couldn't you possibly fit it into your schedule?" Dubley begged. "You wouldn't have to prepare an elaborate lecture-just an off-the-cuff talk would be fine. Our members would eat it up! You might find the meeting interesting. There'll be many people there who have actually seen UFO's."

Tom hesitated. After all, the Saturday night date would not cut into his laboratory working time. Why not go? He might even glean some scrap of information that would help to solve the mystery of the strange flying objects.

"Okay. I'll be there," Tom promised.

The young inventor spent an hour dictating replies to letters. Then he sped to his private laboratory on a jet scooter to finish repairing his aerial telesampler. Luckily, circuit breakers in the system had helped to save the device from any great damage due to the electrical accident.

By early afternoon Tom was ready to give his invention another tryout. He and Bud installed the telesampler in the Sky Queen and took off.

While Bud cruised over the hills west of Shop-ton, Tom sat hunched at the telesampler console in the blister. Time after time he triggered the gun unit. The laser beam drilled into the soil below and the probing microwaves brought back samples of the underlying strata.

Presently Bud asked over the intercom, "How's the prospecting coming along, skipper?"

"Swell! I'm finding all kinds of stuff down there," Tom reported. "Magnetic pyrites, feldspar, barite - even some rock salt."

He chuckled as Bud quipped, "What, no gold?"

By this time, the Queen's zigzag course was carrying them over a wooded valley. "Want me to turn around and go back over those hills again?"

"No, keep going," Tom replied. "Let's sample some of that leafy detritus for a change."

"Leafy which?"

"Rotten leaves and all that moldy gunk on the forest floor."

"Oh - I thought you meant some kind of salad."

Tom soon became engrossed in watching the chemical analysis on the readout panel. Suddenly he frowned and opened the recovery tank to examine the material shown by the last reading.

His fingers brought out some gritty purple dust. "Good night!" Tom muttered in surprise.

His voice carried over the intercom.

"What's the matter?" Bud queried.

"Just picked up some granite, right in the middle of the woods."

"Maybe you hit an outcropping of rock."

"It's possible, but the only place you find granite like this around here is over at Dutchman's Quarry on-"

Tom broke off with a gasp. "Bud, hold it! Go down low and start flying a search pattern!"

Bud was puzzled, but obeyed. The Sky Queen swooped toward the treetops, then banked gently to the right as Bud began steering the huge aircraft on a rectangular search pattern. Tom scanned the ground with electronic binoculars.

Minutes went by. Then Tom shouted excitedly as he glimpsed a figure through the trees below. "Whoa! Far enough!. . . Now come around and ease back toward four o 'clock!"

A few moments later Tom scrambled up into the flight compartment. Bud shot him a startled look. "There's someone down there, sprawled on the ground! Is that who you were searching for?"

Tom gave a hasty nod. "Unless I'm mistaken, he's a boy named Billy Fox. Heard about him on the morning newscast. He was missing after a rock-hunting trip to the quarry."

"So that's it! The granite dust gave you the tip-off!" Anxiously Bud added, "Think he's okay?"

"Don't know. I sure hope sol"

As Bud held the plane steady at treetop level, Tom dropped a nylon ladder and climbed down through the trees. Only a low droning noise came from the Queen, since Bud was using its recently installed repelatrons for hovering, rather than its regular jet lifters.

Tom's heart thumped as he glanced at the motionless figure below. Was the boy injured - perhaps dead? Tom kicked and pushed his way clear of obstructing tree branches, snapping off several as he made his way down the swaying ladder.

As one branch gave a loud crack the boy on the ground stirred. He sat up with a bewildered look, rubbing his eyes. Then he saw Tom and leaped to his feet with a shout of joy! "Hi, Billy!" The young inventor waved and grinned. "Must've been having a real snooze - you didn't even hear our plane pass over!"

Reaching down, Tom hauled the boy up on the ladder. Billy looked a bit frightened at the long climb upward, but Tom circled him with one arm and helped him up, step by step.

Once he was safely aboard the plane, Billy's story came pouring out. His sneakers and slacks were still coated with granite dust from the quarry. "I decided to take a short cut home through the woods," Billy said, "but lost my way. It was awful-especially after it got dark!"

"Think what a story it'll make," Bud said with a straight face, "telling how you fought off all those bears and wolves!"

"You kidding? All I saw was squirrels!"

"Aw, shucks! Do you have to go and spoil it?" Bud chuckled, then he added, "I'll radio Swift Enterprises and have them call your folks."

Billy's father and mother arrived at Enterprises soon after the Queen landed. A crowd of employees surged out on the airfield to cheer and witness the joyful reunion.

Tom, modest as ever, was somewhat red-faced and embarrassed by Mr. And Mrs. Fox's fervent thanks for rescuing their lost son. As soon as he could manage, Tom slipped away and headed back to his laboratory with Bud.

"What's the matter, skipper?" Bud teased. "Don't you like being a hero?"

Tom grinned. "It's okay in small doses."

As the boys entered the laboratory building, loud noises and a crash of breaking glass reached their ears. The sounds came from Tom's lab! "Hey! What's going on?" Bud exclaimed.

The two youths dashed down the corridor to the open doorway of the lab. Inside, two men were fighting wildly!

CHAPTER VIII

MONGOLIAN MYSTERY

"SUFFERIN' sunspots!" Bud gasped. "It's Sam Crivet and Marc Bolen!"

Crivet, an elderly, rawboned man, had a frantic grip on Bolen's throat. The young astrophysicist was desperately trying to beat him off. The two swayed back and forth, bumping against the workbenches and knocking over laboratory equipment.

"Break it up!" Tom shouted, hurling himself at the two opponents.

He blocked Bolen's blows and pushed the men apart while Bud seized Crivet. Bolen seemed only too glad to have the fight stopped, but Crivet resisted fiercely.

"Cool it, Sam!" Tom snapped, his steel-blue eyes blazing. The lab technician, panting and wild-eyed, at last went limp. "What's this all about?" Tom demanded, turning to Marc Bolen.

"Don't ask me. I just found him here in your lab and he went for me like a wild man." The young astrophysicist was still red in the face from Crivet's throttling. The technician's fingermarks showed clearly on his neck.

Bolen said he had been passing the laboratory, saw the door ajar, and heard someone inside. Knowing Tom was out on the airfield, he had gone in to investigate.

"Crivet was over there at the space model of your telesampler," Bolen went on. "Looked as if he'd been sabotaging it. When I spoke to him, he sprang at me and started choking me!"

The huge space model of Tom's new invention - only partly constructed-stood at one end of the room. Tom's jaw tightened as he saw that a tangle of electronic gear had been ripped loose. "All right, let's hear your story, Sam."

Crivet shuddered and rubbed a hand over his eyes. "I'm - I'm sort of mixed up, Tom."

"Take your time and start at the beginning."

"Well, I heard a noise in your lab. Didn't seem right with you gone. I thought there might be more funny stuff going on, like that goat up on the dome, so I knocked and asked who was there. When no one answered, I tried the door. It was open and I went in. Then-wham!"

Crivet winced and fingered the back of his head. "Someone must've beaned me as I stepped inside. Guess I went out like a light. Next thing I remember is fighting with Bolen here." He gave Bolen a dazed, apologetic glance and added, "Don't know what got into me."

Tom and Bud traded puzzled looks. "Did you tamper with my invention?" Tom asked Crivet.

The lab technician shook his head. "I swear I never touched it, Tom!" Crivet paused and gulped. "At least I don't remember touching it."

Tom eyed him thoughtfully. It seemed impossible that an old and trusted employee like Sam Crivet could be lying. "I'd better call Harlan Ames," Tom said. "Then we'll have Doc Simpson look at your head, Sam."

Ames soon arrived, accompanied by a fingerprint man. Afterward, Tom and Bud drove Crivet to the plant infirmary.

Doc Simpson could find no sign of a concussion, but sent Crivet to lie down and rest.

"What do you think, Doc?" Tom asked.

"There's no doubt he received a blow on the head. His scalp shows the bruise."

"That could have happened during his fight with Bolen," Bud pointed out.

"Let's not jump to conclusions," Tom said. "What about his whole story, Doc?"

The medic shrugged. "It seems consistent. If he was knocked out, the blow may have disoriented him. He may have got up in a daze, then turned on Bolen when he came in, thinking Bolen was the person who had struck him."

Later, at the security office, Tom reported Doc Simpson's opinion to Ames. The security chief looked skeptical. "There's another possibility, Tom - a lot more likely, if you ask me."

"Such as?"

"That Crivet's wooziness was just an act. Bolen caught him red-handed, and Crivet panicked. Then, when you and Bud came in, he had to cover up fast, so he pretended to be in a daze."

Tom frowned unhappily. "You think Sam's been our mysterious enemy all along?"

"He left no fingerprints," Ames said, "but I noticed a pair of rubber lab gloves sticking out of his hip pocket. And here's something else-"

Ames opened a desk drawer and took out a workman's time card. "This shows Crivet was on duty Monday night when you were attacked."

Tom was impressed by this added clue. "Harlan, Sam's been working for Dad for over ten years. Why would he suddenly turn against us?"

The security chief shrugged. "Who knows?"

"We still have no proof that he's guilty," Tom argued. "I hate to call in the police as long as there's a chance he's innocent."

"Okay," Ames agreed. "We'll take no action just yet. But from now on I'm going to have Crivet watched every minute!"

Tom had barely returned to his laboratory when a red light flashed on the videophone, which connected to the Swifts' far-flung private television network. Tom switched on the set and Blake, their Washington telecaster, appeared on the screen. He said, "There's a government intelligence report just in, Tom, that John Thurston thinks you ought to hear."

"Let's have it!" Tom said eagerly.

The picture shifted to Thurston, a balding CIA man. "Hi, Tom. We've just had a flash from one of our agents in Hong Kong-about a top-secret Brungarian scientific expedition to Asia."

The camera zoomed in on a wall map. Thurs-ton's finger traced the route. "Our man says the expedition left from Peking and traveled inland by rail to Paotow. From there, they seemed to be heading into the mountains fringing the Mongolian desert. They were gone two months and just returned recently."

"What was the purpose of the expedition?"

"Haven't a clue - in fact, we were hoping you might be able to guess." Thurston added, "From the timing, we wondered if it might have something to do with their comet project."

"Hmm." Tom rubbed his jaw thoughtfully. "Could be, but offhand I don't see any connection - unless they're planning a space facility or tracking setup out in the desert."

Thurston shook his head. "Not likely. Our spy planes would have spotted that."

"Well, anyhow, thanks for the dope, John. By the way, I have a request."

Tom explained that his successful test of his airborne telesampler had given him an idea. He was sure his invention could detect the physical makeup of the UFO's if he could fly to the scene promptly the next time sky disks were sighted.

"That'll require a fast warning system," Tom went on. "So I'd like all law-enforcement agencies, weather stations, air facilities, and defense bases alerted to notify Enterprises immediately the moment the UFO's appear."

"Can do," Thurston promised. 'Til get Defense to set it up."

After switching off the videophone, Tom turned to the space model of his new invention, officially dubbed the Mark III telesampler. The damage seemed not to be extensive, as if the saboteur had been interrupted before he could finish his wrecking job. With Arv Hanson's help, Tom managed to make most of the repairs before leaving the plant that evening.

"I want to make a preliminary test of the circuitry tomorrow, Arv," Tom said. "I'll need a big target mounted on the observatory dome."

"Okay. I'll rig it tomorrow morning."

At home that evening Tom discussed the day's bewildering events with his father. Their chat was interrupted by a telephone call.

Mr. Swift smiled as he hung up. "That was a cable from Dr. Feng, Tom. He'll land at Shopton Airport at six o 'clock tomorrow night."

"Great! I'm eager to find out more about that mysterious manuscript fragment."

Early the next afternoon Tom was ready for his circuitry test of the Mark III. The large device - still in skeletal form with many operating controls not yet installed-had been moved near an open window of the laboratory.

"You say there'll be three gun units on this job?" Bud asked the young inventor.

"Right-for use at different ranges," Tom replied. "Today I'll just test this one that's completed as a check on my circuit design."

Across the grounds, a white plastic target with a red-painted bull's-eye could be seen atop the dome of the Main Building. Tom trained the gun on the red spot, then switched on the telesampler.

Watching through the telescopic sight, he saw a "hole" appear in the bull's-eye, exposing the plastic beneath. The bare space widened as more and more particles of the heavily smeared red paint were carried away by the telesampler's reflected pulses.

Bud, too, watched through binoculars. "She's bringing home the bacon, all right!"

"So far so good." Tom grinned with satisfaction as he opened the recovery tank. To his surprise, it seemed to be empty.

"What's the matter?" Bud bent closer to peer inside the tank.

"The beam hasn't conducted back any of the paint." Tom frowned in puzzlement.

He looked around as his friend gave a sudden choking gasp. The husky young flier was swaying woozily, his face sickly pale.

"Bud, what's wrong?" The words were hardly spoken when Tom himself began to have difficulty in breathing. The room seemed to blur! With a gasp of horror, Tom slammed shut the hatch of the recovery tank and pulled Bud toward the open window. Both boys sprawled over the sill, sucking in lungfuls of fresh air.

At last Tom recovered enough to rush over and switch on an exhaust fan. Then he helped Bud into the hall and outdoors.

"Good night! What happened?" Bud asked weakly.

"I'm not sure yet," Tom confessed, "but I've a hunch the telesampler beam broke down the paint and plastic molecules and allowed them to recombine into some kind of toxic gas in the tank."

Later, after the lab had been aired out, Tom made some chemical calculations. "We both got a whiff of hydrogen cyanide gas," he reported.

"Is that bad?" Bud asked.

"And how! That stuff is poisonous enough to kayo a mule! If I'd had the spectrometer readout hooked up, the analysis would have shown."

"Wow!" Bud whistled, then asked, "Any way to make sure this sort of thing can't happen again?"

Tom nodded, frowning. "Yes, but I'll have to alter the pulse shape and frequency of the beam. It could be a tough redesign problem."

The rest of the day Tom spent hunched over his workbench with a slide rule and pencil. Shortly after five-thirty, with his head still full of circuit diagrams and calculations, Tom left the plant in his low-slung silver sports car and drove to Shopton Airport.

Presently the jetliner arrived from New York. As the passengers came through the gate, Tom hurried to greet a small, slender man with a wispy gray mustache and goatee. "Welcome, Dr. Feng!"

"Ah, Tom!" The little man's wrinkled face creased into a merry smile, slitting the almond eyes which showed his half-Chinese ancestry. "So happy to see you again!"

After shaking hands warmly and collecting Dr. Feng's luggage, Tom led his visitor to the car. Soon they were speeding into Shopton.

"You observe rear-view mirror, I see," said Dr. Feng. "Someone is following us, perhaps?"

Tom grinned. "You have sharp eyes. As a matter of fact, I did think a car was tailing us - a blue sedan back there - but it's probably just my imagination. We seem to have lost it."

"Imagination may at times be a scientist's most valuable ally," Dr. Feng said quietly.

Later, after one of Mrs. Swift's delicious chicken dinners, Tom and his father settled down to chat with their guest in Mr. Swift's den.

"Allow me to congratulate you, Tom, on the comet probe which you are planning," Dr. Feng began. "I have reason to believe a most spectacular comet will soon pass near the earth."

Tom and his father exchanged startled glances.

"A natural comet?" Mr. Swift inquired.

"Quite so. As you know, my father and grandfather both taught at the University of Peking, where I too served on the faculty before I was forced to flee from Red China."

Both Swifts knew that after becoming a refugee, Dr. Feng had gone to his mother's homeland in Western Germany to take a post at the University of Heidelberg.

"We Fengs have always been keenly interested in the work of the ancient Chinese astronomers," the professor continued. "That is how I know of a great comet which was seen by them more than twenty-six hundred years ago, around 650 b. C. My calculations are far from exact, but I believe its orbit should again bring it within view of earth either this year or next."

"That's terrific news!" Tom exclaimed. "If you're right, it may make a good target for my probe, assuming the probe isn't called off."

The Swifts explained to Dr. Feng how the rumored Brungarian comet project might cause the United States space agency to cancel Tom's probe. Tom also mentioned the top-secret Brungarian scientific expedition to Mongolia. "Any idea what they might have been after?" Tom added.

Dr. Feng frowned and stroked his tiny goatee. "At the moment, no. But perhaps I can make inquiries through certain friends of mine still in Asia."

"We'll certainly appreciate it if you can pick up any clues to the mystery," Tom said.

Feng nodded and smiled. "Of course. But now I must tell you the main reason for my visit. I am hoping to persuade you Swifts to undertake an expedition of your own, to solve a much greater mystery - a mystery of outer space!"

CHAPTER IX

BOMB BLAZE

TOM and his father were intrigued by Dr. Feng's announcement. "A mystery of outer space!" Mr. Swift echoed. "You've certainly aroused our curiosity. Tell us about it, Karl."

"Does it have anything to do with that bit of parchment in your letter?" Tom asked.

Again the professor smiled. "Yes, I must confess I sent that along to arouse your interest."

Dr. Feng explained that the fragment was from some old manuscript pages which had recently come into his possession. "They seem to be part of a medieval book on alchemy." He glanced quizzically at the Swifts. "Perhaps you feel the ancient alchemists were merely frauds?"

"Not at all," said Mr. Swift. "Many were gifted scientific workers."

"For that matter," Tom said, "nobody has ever checked out their theories. They may have known more of the secrets of nature than we realize."

Feng nodded gravely. "Their work played a great role in the growth of science. That is one reason why these manuscript fragments may prove most important."

Mr. Swift frowned. "How so, Karl?"

Dr. Feng said he had translated the pages and that they hinted at a secret "school" or center of alchemical study somewhere in Germany. "No such place has ever been found. It was no doubt well hidden. As you know, the alchemists were often persecuted by the law for their work."

"And you want us to help find their secret setup?" Mr. Swift asked.

"Exactly. Think of the old manuscripts and laboratory records it may contain - a priceless historical find! And there is another reason."

"That space mystery?" Tom queried.

"Quite so. What if I were to tell you that this alchemy trove may hold a clue to the weird UFO's now being seen in earth's skies?"

Feng's listeners stared in astonishment.

"What sort of a clue, Doctor?" Tom asked eagerly.

"You may not realize that unidentified flying objects have been seen long before our twentieth century. Many sightings were recorded in the Middle Ages-one at Nuremburg, Germany, in 1561."

Dr. Feng paused. "What I am asking you to believe may sound very strange-yet the manuscript speaks of a definite knowledge of UFO's. One sentence hints that an actual contact was made."

Mr. Swift shook his head doubtfully. "You must admit that sounds rather far-fetched."

"Our own contact with space beings would have sounded pretty strange not long ago," Tom said.

The young inventor bombarded Dr. Feng with eager questions. Then he turned to his father. "Dad, I know this sounds like a pretty wild lead, but I'd like to follow it up."

"In other words, help Karl search for this lost center of alchemical knowledge?"

After a hasty discussion, it was agreed that if the comet project did not interfere, Tom would accompany Dr. Feng back to Germany when the professor returned from attending a meeting of university scholars in Philadelphia.

Suddenly the door chimes rang loudly. Tom went to answer the ring.

The caller was Bud Barclay. "Let's go, skipper!" He blurted. "The plant just got a radio alert from the Oklahoma State Police! UFO's have been sighted near Tulsa!"

Tom's heart pounded at the news. "Be right with you, fly-boy!" He dashed back to the den to tell his father and Dr. Feng of the UFO alert. Both were eager to come and see the spectacle.

In a few moments the group was soaring toward Enterprises in a triphibian atomicar which Bud had flown from the plant. The sleek repelatron vehicle could operate on the highway, on water, or in the air.

At Tom's orders, the Sky Queen had been kept on immediate stand-by. When they reached the airfield, a mechanic reported, "She's all pre-flighted."

The plane dispatcher came rushing out to hand Tom a copy of the IFR flight plan which he had just filed with Air Traffic Control. "I got you a flight level of thirty-nine thousand."

After a hasty checkout and IFR clearance, the Queen was soon spearing upward into the night sky on its jet lifters. Beyond Shopton, Tom rose from six thousand feet to their approved flight level, then gradually increased speed until they were streaking westward at almost Mach 4.

Mr. Swift and Dr. Feng sat in the cockpit behind the two boys at the controls. "I suspect that you Swifts live constantly in the midst of an adventure," the professor murmured. His goateed face wore a Buddha-like smile.

"Tom seems to, I must admit," Mr. Swift said with a grin. "Personally, I'm beginning to prefer a quieter -"

A crewman's voice cut in over the intercom: "The ship's on fire, skipper! Station eight!"

"Ah! You see?" Dr. Feng said calmly. Mr. Swift was too startled to reply.

Tom was already unhooking his seat belt. "Keep her on course, Bud! I'm going aft!"

As the young inventor dashed out of the flight compartment, followed by his father, both snatched up oxygen masks. Clouds of smoke were billowing through the passageway.

The Swifts plunged through the smoke toward a vivid glow beyond. Flames were issuing from the vent louvers in a pair of double bulkheads that formed a partition between two compartments. The crewman was trying to spray Tomasite emulsion into the vents from a portable extinguisher, but most of the foam was splashing uselessly outside the bulkhead. "I can't get close enough!" The crewman shouted through his oxygen mask.

Tom grabbed another extinguisher and tried to help. Heat seared their faces and neither could aim his spray effectively into the vent slits.

"The partition's buckling!" Cried Mr. Swift. The metal was glowing red in several places.

"Quick! Back to the cockpit!" Tom shouted. Mr. Swift and the crewman groped their way after him through the smoke. In the flight compartment, Tom pulled the airtight cabin door shut. "Bud, contact Air Traffic Control and request a change in altitude to fifty thousand feet I Tell them this is a Mayday!"

Bud flung a startled glance at his friend. "Go higher? With a fire aboard, shouldn't we dive and try to land somewhere?"

"I'm going to depressurize. If we can starve the flames of oxygen, it may put out the fire."

Mr. Swift spoke over the intercom to the plane's other two crewmen. "Stay in the power compartment and secure your airtight door!"

The Sky Queen was immediately cleared to the higher altitude. As Bud poured power to the jet lifters, Tom twirled the selector valves controlling the pressurization. Soon dials showed all parts of the ship except the cockpit and power compartment to be losing pressure as the air within equalized to the thin air outside.

After several minutes Tom told Bud to dive to ten thousand feet. Then he opened the airtight door from the cockpit. To his relief, most of the thick smoke had cleared. Mr. Swift accompanied him aft to station eight. Part of the bulkhead had burned through, exposing a still glowing mass of fiery debris.

"Sand will put that out," Mr. Swift said.

The two brought buckets of sand from the laboratory compartment on B deck and soon extinguished the last traces of the blaze.

"Guess we'd better land and check the outer skin of the fuselage," Tom said.

Bud brought the ship down on a bare, rocky plateau, using Tom Sr. 'S latest giant searchlight to illuminate the landing. The plane was thoroughly inspected. Its sturdy structure had resisted the fire with little outside damage.

"Think we can still catch those UFO's?" Bud asked Tom.

"Don't know. Let's check and find out."

A radio call to the Oklahoma police brought disheartening news. The brilliant sky disks had disappeared from view a few minutes earlier.

"What a break!" Bud grumbled to Tom as they flew back to Shopton. "We might have made it in time if it hadn't been for the fire!"

"Could be someone didn't want us to make it."

Dr. Feng's almond eyes narrowed. "You are suggesting that the fire was no accident?"

"More than suggesting," Tom replied. "I'd be willing to bet an incendiary bomb was planted aboard. What do you think, Dad?"

"I'm afraid you're right, son. It was certainly more than an electrical fire - and there are no fuel lines between those bulkheads." Mr. Swift added thoughtfully, "The bomb could have been inserted by removing an inspection plate."

Tom radioed ahead to Harlan Ames. The security chief was on hand to greet them when the Sky Queen landed at Enterprises. Within an hour, a laboratory check of the burned debris proved the fire was due to a magnesium incendiary device.

"It probably was ignited by a timing mechanism," Tom conjectured. "Maybe an inertial device that responded to the plane's motion."

"Another inside job," Ames commented grimly.

Next morning the Swifts drove Dr. Feng to the airport for his flight to Philadelphia. The professor smiled gravely as they shook hands before he boarded his plane. "A most exciting visit - even if we did fail to see any UFO's."

"Can't promise a fire bomb every time, but we do our best," Tom joked. "Don't forget to stop back - I'm looking forward to Germany!"

Tom spent most of Saturday in his laboratory, hard at work on his space telesampler. That evening he and Bud took the girls to dinner at a restaurant, then drove to Racklin Hall for the UFO Study Club meeting.

Hubert Dubley, the president, was a stout, bald-headed man with horn-rimmed glasses. "We're honored to have you here!" He told Tom.

All sorts of people were crowding into the auditorium-businessmen, housewives, students, and a few who looked like cranks or fanatics. An elderly woman waved. Tom smiled and waved back as he recognized Mrs. Abernathy.

Bud nudged him. "Look who just came in!"

Tom was startled to see Sam Crivet taking a seat at the back of the hall. Presently Dubley asked Tom to come up on the platform with him. Bud, Sandy, and Phyl sat down in the front row.

The meeting began with reports on UFO sightings. Several people who had seen the flying disks stood up to tell about their experiences. Tom listened with keen interest. Then Dubley invited the young inventor to speak.

"I've been asked to discuss extraterrestrial life," Tom told the audience. "There's no doubt life does exist outside of earth, because my father and I are already in touch with creatures living elsewhere in our solar system-although as yet we know very little about them.

"Many of you seem to believe the UFO's may be spacecraft manned by intelligent beings. Our information so far is too limited to decide. However, within the near future, space probes should tell us a good deal about the chances of finding life on other planets."

Tom went on to talk about physical conditions on Mars, Venus, and the other members of earth's solar system. Afterward, Hubert Dubley invited the audience to write out questions. An usher brought them up to the platform.

The young inventor read and replied to several questions. His eyes widened in surprise as he glanced at the next slip o£ paper. It said:

PLEASE DON'T READ THIS ALOUD - IT WOULD EMBARRASS ME TO HAVE MY NAME CONNECTED WITH UFO's AND ALSO CAUSE A RUSH OF CURIOSITY SEEKERS. I CAN SHOW YOU A SPOT WHERE UFO'S DEFINITELY LANDED AND LEFT TRACES IF YOU COME TO RABBIT RIVER MILL AT 11 TONIGHT.

J. BASCUM

CHAPTER X

A STARTLING SKYROCKET

WAS Bascum's message a hoax - or had the UFO's really made a secret landing in the area? Tom's pulse raced as he tucked the hand-printed note into his pocket and went on to the next question.

At last Dubley stood up to close the session. Tom said hastily, "Will Mr. J. Bascum please see me before he leaves the hall?" He scanned the faces of the audience but no one responded.

As the meeting ended, people swarmed up on the platform to chat with the young inventor and ask for his autograph. Tom good-naturedly obliged. It was some time before Dubley could dislodge his guest from the knot of eager fans.

"Thanks - I wasn't sure I'd be able to pry myself loose." Tom grinned and wiped his perspiring forehead with a handkerchief. "By the way, do you know anyone here named Bascum?"

Dubley squinted thoughtfully through his horn-rimmed glasses. "No, he's not a club member. And I don't recall seeing any such name in the visitors' book. Of course many don't sign."

As soon as the young inventor left Racklin Hall, he showed the note to Bud and the girls. Bud whistled. "What do you make of it, Tom?"

"Don't know, but it sounds interesting."

"If you ask me, it sounds queer!" Sandy said. "You're not going there, are you?"

Tom rubbed his chin reflectively. "Maybe - but not until I've showed this to Harlan Ames."

From a public telephone booth, he called the security chief. "I'll meet you at the plant in twenty minutes," Ames said tersely.

The boys drove Sandy and Phyl home, then sped to Enterprises. Ames was waiting in the security office. He listened to Tom's account of the UFO club meeting and read the message intently. Then he checked the telephone directory. No "J. Bascum" was listed.

"That doesn't prove much," Tom pointed out. "He may not have a phone - or he may have come from some place quite far from here."

"He may also be a phony, trying to lure you into a trap." Ames frowned and began pacing about the office. "If Crivet was there, he could have written the note."

"But surely Crivet's in the clear, isn't he?" Tom argued. "If you've been having him watched, he couldn't have planted the fire bomb on the Sky Queen."

"I'll admit I can't answer that one," Ames said, "unless he has a confederate. Anyhow, let's check some samples of Crivet's-"

He broke off to answer the telephone. Ames's face flushed with anger as he hung up. "Great!"

"What's the matter?" Tom asked.

"That was the operative who's been shadowing Crivet. He just lost him in a traffic jam."

"Was Crivet trying to give him the slip?"

"He doesn't think so, but he's not sure."

Tom glanced at the clock. Its hands showed 10:24. "Harlan, I'm going to keep that rendezvous at the mill. If there was a UFO landing, it's too important to pass up. If the note's a trick, maybe we can trap the sender."

Ames scowled tensely. "Okay, we'll play it your way, Tom - but we won't take any chances."

The security chief picked up the telephone again and began issuing hasty orders. He arranged for half a dozen security men to approach the spot secretly from another direction. Ames and Bud would be with them. Tom, meanwhile, would drive there openly and await "Bascum."

It was three minutes to eleven when the young inventor stopped his car near the Rabbit River mill. The old stone structure, with its broken water wheel, loomed silently in the moonlight.

Tom sat still for a moment, listening. The only sounds were the breezy rustle of trees from the surrounding woods and the rippling of the river. Finally he got out of the car and shone his flashlight around inside the mill. The building seemed empty.

Tom wondered if Bud and Ames and the others had taken up their positions yet. "They sure didn't have much time," he thought.

Minutes passed. Suddenly a skyrocket shot up through the darkness! It burst overhead with a loud report, showering red and blue sparks. An instant later came two muffled shots!

Tom sprang into action. He raced through the trees toward the sound of the shots, which seemed to have been fired a short distance downstream.

The glare of a flashlight suddenly dazzled his eyes. "Tom!" It was Ames's voice.

"What happened, Harlan?" Tom asked tensely.

Before the security chief could answer, they heard a rush of footsteps through the underbrush. Figures materialized out of the darkness. One by one, Ames identified them. They were the other security men and Bud.

"Looks as though we blew the whole deal," Bud said ruefully.

"We sure did," Ames rasped in disgust. "That skyrocket and the shots were a trick to make us show our hand."

"Whoever fired them can't have gotten far," Tom declared. "Let's spread out and search!"

The Enterprisers fanned out through the trees. Ames radioed the plant to send Whirling Ducks. Soon the helijets were skimming over the woods, sweeping the terrain with giant searchlights.

But their efforts proved fruitless. Long past midnight, the hunt was abandoned after turning up no trace of the mysterious "Bascum."

Monday morning Ames told Tom that Sam Crivet was still under suspicion. The security operative had seen him return home about midnight.

"Crivet claims he drove to Greenville to visit an old friend," Ames said, "but the friend wasn't home, so he came straight back to Shopton."

"Does his story check out?" Tom asked.

"Yes, but it's not exactly an airtight alibi." Ames frowned and tugged his lower lip thoughtfully. "The big mystery to me is how 'Bascum' slipped through our fingers."

"I think I can answer that," Tom said. "He probably came and went by the river - in a frogman suit." Ames's jaw dropped in dismay.

Tom spent the following days working intently in his laboratory, completing and checking the design of his Mark III telesampler. By Thursday, when Dr. Feng returned from Philadelphia, Tom felt that the space model of his invention was well enough along to be turned over to Arv Hanson and the engineering crew.

Sandy had begged to come along with Phyl on the trip to Germany. Thursday night all members of the group retired to comfortable compartments aboard the Sky Queen at the Enterprises airfield. The next morning when the girls awoke, the huge airplane was already winging over the Atlantic at supersonic speed.

Soon after noon, Middle European time, the Queen set down on a small field at Sembach, northwest of Heidelberg. Chow Winkler served them a tasty lunch. Then Tom's group skimmed over the countryside toward the famous old university town in an atomicar, which had been transported in the plane's spacious hangar compartment.

As they approached Heidelberg, Sandy and Phyl were overwhelmed by the beauty of the scene. The town nestled on the River Neckar in a valley of the green-wooded Odenwald Mountains. Above it towered Heidelberg Castle. The river, which flowed westward into the Rhine plain, was spanned by picturesque bridges, with white-winged sailboats cruising on its placid blue surface.

"Golly!" Phyl sighed. "Heidelberg must be the most romantic university town in the world!"

Dr. Feng smiled and nodded. "Many American writers, such as Washington Irving, Longfellow, and Mark Twain, have said the same, my dear."

Bud immediately began chortling a song from the famous operetta The Student Prince. Sandy covered her ears. "Please I Let's not get that romantic!"

Nearer than the huddled red-slate roofs and old church spires rose a slender, modernistic tower. "That's the Mengler skyscraper," Dr. Feng said. "This area to the north and west is the newer part of Heidelberg."

Tom brought the atomicar down on an avenue running along the river. Then he drove on into the Hauptstrasse, or main street. The narrow thoroughfare was crowded with traffic. Students whizzed by on motorcycles and motor scooters.

Dr. Feng deposited his luggage at his private lodgings. Afterward, he guided the teenagers around the Old University and New University. The latter, he said, had been built partly with American funds. "Actually, Heidelberg has no real campus. Its buildings are scattered all over town, on both sides of the river. These are only a part of the whole university."

Feng told them Heidelberg had over twelve thousand students-many of them from foreign countries, including several hundred Americans. "And about a quarter are now girls."

"Phooey!" Said Sandy. "That spoils another romantic dream."

"Who's complaining?" Bud retorted with a grin, eying the pretty female students who were lounging about the grassy courtyard of the New University with their books and friends.

Sandy and Phyl were entranced as they strolled about the cobbled streets of the Altstadt, or Old Town, with its quaint baroque buildings.

Dr. Feng showed his guests the ancient Gothic-style Church of the Holy Ghost. Then he glanced at his watch. "Perhaps it is time for some refreshment."

The professor took the teenagers to an old medieval-looking tavern, where they ordered sandwiches. The room was dark with smoke-stained oak beams. Musicians were playing at one end of the room and couples were dancing.

Tom noticed a group of male students around one table. They wore small, narrow-visored fraternity caps and broad sashes of gold, silver, and black across their chests.

"They belong to one of the old student corps," Dr. Feng explained. "But nowadays such fraternities have gone rather out of fashion."

The two American girls drew admiring glances from the group. A tall, handsome student, with close-cropped blond hair, seemed particularly taken with Sandy. "Entziickend! Lovely!" He muttered aloud. Bud growled angrily.

Finally the student arose and came over to their table. Smiling, he made a quick bow and said to Sandy, "If I am not too bold, perhaps the gnadige fraulein would care to dance?"

Bud jumped up from his chair. "Sorry, pal, you're too late. She's dancing with me."

The student's smile froze. "I was speaking to the gnadige fraulein. Shall we allow her to choose?"

Bud reddened. "You heard me, buster. Now if you'll please step out of our way-"

Sandy smiled and murmured hastily, "Bud, please don't be silly!"

Her remark only seemed to irritate Bud further. He started to elbow the student aside. The young German curtly brushed his arm away. Bud, already at boiling point, mistook the gesture for an intended blow. His fist lashed out and caught the student squarely on the jaw.

The German youth was knocked backward. He straightened up, eyes blazing. "You will pay for that gemeiner fie gel!" He hissed at Bud. "If you are not too much of a coward, we shall settle this quarrel with dueling sabers!"

CHAPTER XI

DEADLY WEAPONS

"ANY time you like!" Bud retorted to the student who had challenged him to a duel.

Tom sprang to his feet. "Look - this has gone far enough! Nobody fights duels nowadays."

The student eyed Tom scornfully. "I can see that you know nothing about Heidelberg."

"It's ridiculous!" Sandy insisted. "Please, Bud, can't you just apologize to him?"

"Apologize? He's the one who came barging over where he wasn't wanted!"

The blond youth plucked a card out of a pocket and handed it to Bud. "I shall meet you at the Grime Jaeger. It is an inn on the Neckar above Heidelberg. Shall we say six o 'clock?"

He clicked his heels and bowed stiffly to Sandy and the others, then returned to his own table. Soon he was laughing and talking with his companions. The tavern owner, who had bustled forward, also shrugged and walked off.

Sandy seemed on the verge of tears. Phyl tried to comfort her. Dr. Feng was the only one at Tom's table who had remained completely calm. "Most unfortunate," he murmured.

"Good grief," Tom said. "This sort of thing doesn't still go on in Heidelberg, does it?"

"Officially dueling is forbidden," Feng replied, "yet duels still take place among fraternity students. The worst that results is usually a small facial scar. I think perhaps the young man would not have issued the challenge if he had recognized me as a member of the faculty."

"Isn't there any way you can stop it?"

The professor's eyes were troubled as he tugged his goatee. "I could of course report the incident to the university authorities-"

"Nothing doing!" Bud snapped. "That creep would think I wanted to worm out of the duel." He glanced at the card and read the student's name aloud. "Wolf von Enzbach - sounds like someone out of an old Hollywood movie."

Dr. Feng looked startled. "I have heard of this fellow before. He is the son of Graf von Enzbach - what you would call the Count von Enzbach. He is also the best fencer at the university!"

"Oh, no!" Sandy gave a little wail. "Bud, you just can't go through with this!"

"Why not? What kind of a Galahad would I be if I can't fight for my fair lady!"

All the same, as they left the tavern, Tom thought his pal looked a bit apprehensive. "Sure you won't change your mind?" Tom asked.

Bud shook his head stubbornly and glanced at his wrist watch. "I still have about an hour and a half. Look, would you girls please excuse me? There's something I'd like to do."

Sandy had been whispering to Phyl. "Go right ahead - don't mind us," she replied airily. "We want to do some shopping."

Bud seemed hurt as the girls walked off. "How do you like that? Doesn't sound as if she's very worried about me getting sliced up!"

Tom grinned. "Make up your mind. Do you want her to beg you to call off the duel or not?"

"Let's say I don't mind if she wrings her hands a few times."

"Okay, I'll make a note of it. Now what?"

"How about finding a fencing master, so I can get a few tips?"

"Are you kidding?" Tom blurted. "Nobody can teach you how to duel in one easy lesson!"

Bud said gloomily, "At least he can show me how to hold a saber, so I won't look too silly."

Dr. Feng knew of a fencing academy in the Altstadt, several blocks from the tavern. He led the way. In a few minutes they reached a doorway which bore a brass plate reading: FECHTSCHULE Wilhelm Holz, Maitre d 'Armes The three climbed a rickety flight of stairs. Sounds of stamping feet and clashing steel reached their ears. On the floor above they found themselves in a wide hall. Several students were engaged in practice bouts, wearing wire masks and padded chest protectors, or plastrons.

A man walked over to greet the three visitors. He was wiry but bull-necked, with a shaven head and a face seamed with tiny scars.

"Herr Holz?" Said Dr. Feng. He hastily explained the situation and introduced Bud and Tom.

Holz scowled and looked Bud up and down. His expression was not encouraging. Finally he led Bud over to a wall rack, where various items of equipment were hanging, and proceeded to outfit him with mask and weapon. Then, with a saber of his own in hand, Holz began the lesson.

Bud was a fine athlete, but football, basketball, and baseball had given him little aptitude for fencing. Holz was soon bellowing at the American youth in a vain effort to get him to handle the saber a bit more deftly than a baseball bat.

"Ach, du Hebe giite!" The fencing master shouted. "Hoffnungsloser fall! A hopeless case!"

At the end of an hour's instruction, as Bud was hanging up his equipment, Holz rolled his eyes and muttered to Dr. Feng, "Sein Kopf wird ausse-hen wie ein Rangierbahnhof von all den Schmis-sen!"

"What did he say?" Tom whispered.

"He says with all the cuts Bud will get, his head will look like a crisscross railroad track!"

In glum silence, the three left. Downstairs, on the cobbled pavement, Tom again tried to persuade his friend not to go through with the duel.

"Quit trying to talk me out of it!" Bud said. "Don't you think I know what I'm getting into?"

The two boys and Dr. Feng returned to the atomicar. Sandy and Phyl were not in sight.

"Come on! Let's get going before I lose my nerve!" Bud urged shakily.

Tom took the wheel and Dr. Feng guided the way to the place appointed for the duel. Presently they arrived at a rustic inn, perched on the eastern slope of the Konigstuhl mountain, overlooking the river. A weather-beaten sign hanging over the door bore the legend: zum grunen jaeger, with a picture of a green-coated huntsman.

Bud gulped as they climbed out of the car, but said nothing. He was looking rather pale.

Inside, Wolf von Enzbach was waiting at a table with several other students. "Ah, you are most punctual!" He smiled and stood up. "Some refreshment, perhaps?. . . No?. . . Then if you are ready, let us proceed."

"I'm ready," Bud said curtly.

The stout landlord pretended to busy himself at the counter as they filed into a back room. Two dueling sabers were laid out on a bare oak table - the only item of furniture.

"You are quite sure you would prefer not to apologize for striking me?" Enzbach inquired.

"Let's get on with it!" Bud growled.

"As you wish." The blond youth began to explain the formal procedure for the duel.

Suddenly a babble of voices was heard from the main outer room of the inn. Then the door burst open and Sandy and Phyl came rushing in breathlessly. Both were pink-cheeked with excitement. Sandy was carrying a long, narrow parcel.

"Wait!" She cried.

Wolf von Enzbach smiled at her in surprise.

Sandy spoke to him abruptly. "Since you were the one who challenged my friend, he has the right to choose the weapons - isn't that so?"

Enzbach's face took on a puzzled frown. "Yes, that is correct, gnadiges jraulein, but-"

Sandy's eyes swung to Bud. "All right then, choose these!" She held out the parcel.

"What's in there?" Bud asked blankly.

"Never mind arguing, Bud Barclay! If you ever want me to speak to you again, do as I say!"

Bud shrugged. "What have I got to lose?"

He took the parcel and started to undo it. A moment later his lips twitched. Inside the wrapping paper were a pair of rubber swords!

Enzbach's mouth dropped open. One of his friends started to chuckle. The next instant Enz-bach himself burst out laughing.

"Very well, if that is your choice." He seized one of the rubber swords. "En garde!"

Bud took the other and they crossed swords both blades bending backward as they did so. The fight began furiously. Everyone in the room was soon roaring with laughter.

Wolf's blade feinted and slashed with dazzling speed. Before long, Bud's face was crimson as his opponent's rubber sword slapped him smartly again and again. At last, with a single sweeping blow, Wolf von Enzbach knocked the sword from Bud's hand.

The room shook with applause and cheers.

"And now," said Wolf, "since your face is as red as mine, perhaps we can shake hands and be friends."

In spite of feeling foolish, Bud was unable to keep from laughing. He thrust out his hand. "Fair enough, pal! Now that our duel's over, I don't mind saying I'm sorry about that sock in the jaw. Guess I was being a bit hasty and bad-tempered."

Wolf bowed in Sandy's direction. "And I apologize if my admiration for the fraulein made me seem too bold."

He turned back to Bud, grinning impishly. "Your fencing master telephoned the inn and asked me not to mark you up. But his call was quite unnecessary. I never intended to do more than make you perspire a bit. You are a brave fellow, and if you should ever enroll at the university, my friends and I would be honored to have you join our corps."

"Great! But I sure wish you'd told me that sooner. I'll bet I lost ten pounds worrying about the plastic surgery I'd need after you finished carving your initials in my face!"

"What about the rest of us?" Said Phyl. "Poor Sandy was almost frantic, trying to find a toy shop in town that carried rubber swords!"

After the laughter had died down, introductions were performed. Wolf and his friends were highly embarrassed to learn that the goateed gentleman in Bud's party was a professor. They were also much impressed at meeting the world-famous young inventor, Tom Swift.

As they ate supper at the inn, Tom explained why he had come to Germany. Dr. Feng told how he had learned of the secret alchemy center from the old manuscript fragments.

"The center was dedicated to Mercury, the legendary messenger of the gods," the professor related. "One sentence in the manuscript states that Mercury himself dwells nearby and that his sign points the way to their portals."

"Professor Feng!" One student spoke up. "That may refer to the hill across the river in Neuen-heim - the Heiligenberg! In Roman times a temple to Mercury stood there."

Feng nodded. "Quite so. That was my first idea, also. But I have searched the Heiligenberg carefully without finding a clue."

"What do you intend to do now?" Asked Sandy.

"In my opinion," Feng explained, "the sentence may mean that the alchemy center was located near a deposit of the metal mercury. The chief ore of mercury is cinnabar-which often occurs near the outlet of hot springs. Therefore I suspect that the hidden site may be near one of our numerous German mineral spas."

"Have you gained any further clues?" Wolf von Enzbach inquired.

"As yet, no. But I am hoping that Tom's scientific genius may unearth the site."

Professor Feng added that he was also still studying the fragments of the manuscript, whose leaves bore the Latin title: Liber Reginae Albae - The Book of the White Queen. " 'The White Queen,' you see, was the secret alchemical name for mercury."

Wolf gasped. "What you say is most interesting, Herr Professor! I am quite sure that I have often heard of something called 'the White Queen' near my home!"

CHAPTER XII

A GHOSTLY KNIGHT

TOM and his companions were startled by Wolf's remark. "Can't you remember what the name refers to?" The young inventor asked.

Wolf frowned and shook his head slowly. "Nein. But it is possible that my father or one of our old family servants would know."

The blond youth looked up with a sudden smile. "I was intending to return home for the weekend tomorrow. Why not come with me - all of you! Our family castle is less than two hours' drive from Heidelberg, and my father would be delighted to have you as guests."

Tom glanced at the others in his party. All were intrigued by the invitation. "That's certainly kind of you, Wolf," he said.

It was agreed that they would leave the next day after lunch.

Saturday morning Wolf and one of his friends took the girls on a tour of the castle, or Schloss, overlooking the town. The huge red sandstone ruins had once been the home of the Palatinate Prince-Electors. Wolf told Sandy and Phyl it had been wrecked three hundred years ago by a French king's army.

"A good thing, perhaps," he added with a chuckle. "As you see, it was built in such a jumble of styles it makes a more beautiful ruin than it was a piece of architecture."

Through the pillars of the castle's Scheffel Terrace, they gazed out over the valley, the river, and the town rooftops to the Rhine plain far beyond. "This terrace was named after a poet - Josef Victor von Scheffel," Phyl's escort said. "He wrote the words of many of our favorite student songs here at Heidelberg."

Torn had been eager to see the university's scientific facilities, so Dr. Feng showed him and Bud its world-famous Institute of Physics, and the glittering chrome-and-glass laboratories of the Max Planck Institute for Medical Research.

"The science courses here are very strict," Feng explained. "But students in other fields are free to study as they please. They can even decide for themselves when to take exams."

"Wow! That's for me!" Bud exclaimed with a grin.

After lunch the group started out on their weekend trip to Schloss Enzbach. Wolf led the way in his racy Porsche sports car, taking Sandy and Bud. Tom followed in the atomicar with Phyl and Dr. Feng.

Their route led through the lovely Odenwald Mountains. Barely outside of town Phyl glimpsed wild deer feeding among the tangled greenery of the slopes. The mountainsides were terraced with vineyards, and the air was sweet with the scent of grapes and berries. "In fact," said Dr. Feng, "Heidelberg probably got its name from Heidel-beerberg, meaning Huckleberry Hill."

Later in the afternoon they came to the small, ruggedly built gray castle which, for several hundred years, had been the ancestral home of Wolf's family. As they parked in the courtyard, his father came out to greet the visitors.

Count von Enzbach was a thickset, kindly looking man, with a huge, curving "Kaiser Wilhelm" mustache. He wore a monocle in one eye and walked with a cane. Phyl liked him at once, but had to stifle a giggle as he bowed and brushed her and Sandy's fingertips with his mustache.

Then he shook hands warmly with Dr. Feng, Tom, and Bud. "Schloss Enzbach is honored!"

Tom waited until after dinner to bring up the subject of the White Queen. Count von Enzbach looked so surprised that he almost dropped his monocle into his coffee. "Na so was! I have not heard that name in years!"

"You recognize it, Graf?" Dr. Feng asked.

"Jawohl! Of course! It is the old, old name for a hill near here." The count rose from the table and pulled aside the heavy red-velvet drapes from a window. The others gathered around and gazed out across the moonlit valley. "You see that hill near the horizon? Berg der Weissen Konigin, it was called - the Hill of the White Queen."

"Do you know why, sir?" Tom asked.

Count von Enzbach shook his head. "Nein. In fact, I had quite forgotten the name until you mentioned it. However, I can tell you that an ancient monastery once stood on the hilltop. Later it was used as a crude observatory for studying the stars, but there is not much left of it now except the crumbling walls."

Tom and Dr. Feng were excited by this information. They immediately laid plans to visit the spot the next day.

Sandy and Phyl were assigned a lofty room together, with a huge stone fireplace. Late at night Sandy awoke, thinking she had heard a door creak.

Tensely she reached out for her small flashlight on the night stand and beamed it through the darkness. The next instant Sandy gave a startled scream!

A helmeted head was peering in through the doorway!

Phyl sat bolt upright in bed beside her. "Sandy! What's wrong?"

"I just saw someone wearing a knight's helmet!" Sandy cried. "Right there at the door!"

Phyl was half incredulous and half fearful. "Y-y - you mean a ghost?" She quavered.

"I don't know! Let's look!" Courageous as always, Sandy sprang out of bed and pulled on her robe. Phyl did the same and dashed after her into the hall. Their own room, like many other rooms in the old castle, had no electric lights, but Sandy knew that the corridor did. Using her flashlight, she found the switch and pressed it.

The boys and Dr. Feng, aroused by Sandy's scream, were already peering out of their rooms farther down the hall. But the helmeted prowler was nowhere in sight! Wolf, his father, and several servants soon arrived on the scene. All listened to Sandy's story in amazement.

"It is true there is an old legend of a ghost haunting Schloss Enzbach, but-" The count paused. Frowning, he stroked his huge mustache. "You are quite sure you did not dream of this ghostly knight, liebes kind?"

"Positive! I was wide awake!" Sandy declared.

A hasty search was made, but no intruder was found. Tom was thoughtful as he and Bud went back to their room. "If Sandy's right," he said, "someone may have been trying to search our rooms."

The boys checked the small flight bag in which they had brought a change of clothing. Its jumbled contents showed that someone had groped inside it! Several pockets in the boys' clothes had also been turned out.

"He must've come here before Sandy spotted him," Bud said. "Wonder what he was after."

"Anything worth taking, maybe," Tom said.

The next morning Wolf showed his guests a visored helmet. "That's what I saw!" Sandy exclaimed.

"One of the servants found it in the courtyard," Wolf said. "It came from a suit of armor in the main hall. Our unwelcome visitor must have worn it to mask his face."

"How did he break into the castle?" Tom asked.

Wolf smiled ruefully. "He would not have had to - our doors are never locked. I apologize to all of you - and to you especially, Sandy-for this unpleasant disturbance of our weekend."

Sandy's blue eyes twinkled. "To be honest, I rather enjoyed it - it was so exciting!"

The Von Enzbachs and their visitors attended church service in the nearby village. Then, after lunch, they all set out for the Hill of the White Queen in the two cars.

Little more remained of the old monastery than a few broken walls, overgrown with moss and creepers. Tom and his companions combed the ruins for hours without finding a clue to the secret alchemy center. But Tom felt certain the name of the hill was no mere coincidence.

"I think we should check this whole terrain for any mercury deposit," he told Dr. Feng.

"Can that be done readily, Tom?"

"Sure. As soon as the Sky Queen gets here." Feng was delighted when the young inventor explained the operation of his telesampler.

After Tom had radioed the Flying Lab, the group started back to the castle. This time the atomicar - which had been parked behind Wolf's Porsche-led the way down the narrow, precipitous dirt road. Tom drove with the count beside him, and Phyl and Dr. Feng in back.

The road, in places hardly more than a ledge, wound steeply down the hill. Suddenly Phyl gave a cry of fright. "Tom! That boulder-!"

Tom had glimpsed it out of the corner of his eye that same instant. The huge stone was rolling down the slope out of the underbrush, above and ahead of them to the right!

"Um Himmelswillen! It will crush us!" Shouted the count.

Tom's heart hammered and his hands clutched the control lever. If he tried to slam on the brakes, they were likely to collide with the giant mass of rock!

CHAPTER XIII

SIGN OF MERCURY

RECOVERING from his split second of panic, Tom hauled back on the control lever. The bubble-domed atomicar leaped upward like a frightened frog! It cleared the down-rushing boulder and hovered high in the air above the cliff.

Below them, the huge rock landed on the road like a clap of thunder, then rebounded in a cloud of dust and hurtled on down the embankment! Wolf, speeding along behind the atomicar, had seen the near disaster. His yellow Porsche screeched to a halt.

"Oh!. . . Oh dear!" Phyl gasped in a choking voice. She clung weakly to Dr. Feng.

Tom glanced at the count. His face was ashen and his monocle had popped out of his eye. "Ach du lieber Himmel!" He croaked.

A flash of realization came to Tom. "Good night! I'm terribly sorry, sir! I guess I forgot to tell you this car could fly!"

"Ja!. . . Quite so, my boy." The count mopped his temples with a handkerchief. "I am most thankful you did not forget how to make it fly!"

Tom landed hastily. Wolf, Sandy, and Bud jumped out of the Porsche and ran to the atomi-car. The count was badly shaken, and his monocle still dangled limply from its cord.

"This weekend seems to be - how do you say?--Jinxed," Wolf said apologetically. "First that ghostly intruder last night, and now this near accident."

"If it was an accident," Tom said, scanning the wooded slopes thoughtfully.

The others were startled by his remark. "Are you implying that someone may have dislodged that boulder on purpose?" Wolf asked.

"Could be," Tom replied. "Maybe the same person who wore that helmet last night. There's plenty of cover up there on the hillside."

"But - but how could he have known that we would be coming along this road?"

"Easily. He could have watched us through binoculars when we drove up the hill, and then followed while we were searching the monastery ruins. After that, all he had to do was wait."

The three youths climbed the rugged, tree-clad slope to scout for clues. They found the spot from which the boulder had come loose, but if anyone had pushed it, he seemed to have left no traces.

Soon after they arrived back at Schloss Enz-bach, the Sky Queen came winging in from Sem-bach. The huge plane made a startling sight, hovering near the walls of the old medieval castle. The count's servants gawked in astonishment.

Tom went aboard and took over the controls from Slim Davis, a Swift test pilot who was acting as crew chief. Bud, the girls, Wolf, and Dr. Feng accompanied the young inventor. The count had declined, saying he had enough flying for one day.

The Queen streaked toward the Berg der Weis-sen Konigin. When they reached the hill, Tom crawled down into the blister and switched on his aerial telesampler. He aimed the gun unit at the ground as Bud maneuvered in slowly widening circles about the monastery ruins.

"Bud! Hold it!" Tom called over the intercom. His eyes were fixed on the readout panel. Then he opened the recovery tank.

Tom's face was flushed with excitement as he climbed back into the cockpit moments later.

"You have found mercury ore?" Dr. Feng blurted. "Cinnabar, perhaps?" His goatee quivered eagerly.

"Not ore! Pure mercury!" Tom held up a small plastic scoop. It contained a blob of glistening silvery substance!

The professor's eyes bulged. "Incredible! Can you identify the exact spot?"

"Probably within about ten square yards."

SIGN OF MERCURY ITS While Slim Davis took the controls, a ladder was lowered to the hillside. Tom, Bud, Dr. Feng, and Wolf scrambled down hastily.

"Over here, near this rock!" Tom cried, leading the way. "The stuff came right off the surface of the ground, or close to it!"

All four had brought machetes from the Queen's tool locker. They spread out, hacking away at the underbrush and probing among the tall grass. Dusk was gathering as the sky reddened over the western reaches of the Odenwald. Presently they were forced to use flashlights.

A shout from Wolf brought the others running toward him. "I've found it!" He cried out.

Tom gasped when he saw the metallic traces in the soil. The mercury glittered in the rays of Wolf's beam. "Looks as if it runs in a stripe or band," Tom observed. "Let's follow it."

Step by step, they traced out the path of the mercury. It curved in a complete circle. Just above this and touching it was a shallow, half-moon curve. Below the circle was a cross.

"The alchemical symbol for mercury!" Dr. Feng exclaimed in awe.

"We must be near the alchemists' secret center!" Tom declared.

But where was it? The four stared around in bewilderment.

"Too bad we found this so late in the day," Bud said. "It'll soon be too dark to look."

"That's no problem. We can switch on the Queen's searchlight!" Tom shouted an order up to the crew of the hovering sky giant.

Bud was pacing about restlessly. Just as the Queen's light came on, bathing the hillside in radiance, the others heard him yell.

Bud had almost disappeared from sight! Only his head and shoulders showed above the brush. "Come quick!" He shouted. "There's some kind of cave opening here! I fell right into it!"

Tom's heart gave a leap. "That must be what we're looking for! The tail of the symbol points right toward it!"

Bud was already probing deeper into the opening as the others trampled the shrubbery aside and crowded in behind him. They were in a tunnel, walled with earth and rock which burrowed down into the hillside at a gradual slope.

Suddenly Bud stopped. Tom, Wolf, and Dr. Feng clustered around him. All four gasped at the sight revealed by their flashlight beams. Ahead lay a huge natural cavern, pillared with stalagmites and stalactites. The chamber was filled with ancient alchemists' equipment!

"We have found it!" Feng cried in a trembling voice. "The hidden center of alchemical knowledge!"

He strode into the cavern. Arranged about the floor were brick athanors, or furnaces, with bellows and tongs hanging ready for use. Flasks, crucibles, retorts, pelican jars, and coiled distilling apparatus stood everywhere. Several long wooden tables bore bottles, mortars and pestles, and earthenware vessels. A number of oil float lamps hung on chains from the roof of the cavern.

Tom was intrigued by several tripod-mounted telescopes. Evidently the occupants of the tavern had mingled astronomy with their alchemical studies! Dr. Feng was more interested in the shelves of ancient leather-bound volumes and papyrus scrolls lining the walls.

"What a treasure trove!" The professor gasped. He dared not open the books for fear their mildewed pages would crumble to the touch. He read off several of the famous titles: The Great Mirror of the World, Stairway of the Sages, The Magnum Opus Unveiled, The Book of the Twelve Gates. Many of the others, he said, were totally unknown to historians of alchemy.

Beyond, the cavern forked into two passageways. "Wonder what's back there," Bud said.

He and Wolf were about to explore when Chow's voice suddenly drew everyone's attention. The plump cowboy cook came waddling excitedly into the cavern from the outer tunnel.

"Tom! Come back quick!" He bellowed.

"What's wrong?" The young inventor asked.

"We just got a radio flash from the United States Air Force Command in Europe!" Chow said. "They've sighted a flock o 'UFO's over Spain!"

Tom was electrified by the news. At Dr. Feng's urgent pleading, they gathered up as many volumes as they could carry and had them hauled up in a bag to the Sky Queen. Then they clambered aboard.

Tom immediately got the details of the sighting over the radio. The Air Force general who had flashed the alert reported that a brilliant display of flying disks was sighted over San Sebastian on the Bay of Biscay. "I'm issuing a priority to have your plane cleared all the way, Tom!"

Soon the Flying Lab was on its way, streaking high over Germany and France. It reached the west coast of France and passed over the bay. Presently the dazzling red, blue, and yellow disks became visible in the night sky ahead.

Tom's heart thumped. Not only would he soon analyze the UFO's, but perhaps the Queen could even make contact with the strange objects!

CHAPTER XIV

SKY SPOOKS

TOM switched on a television camera which would automatically record on videotape the maneuvers of the UFO's. "Okay, Bud-take over! I'm going down to the blister!"

"Roger!" Bud responded.

Tom crawled down the ladder and squirmed into the bucket seat at the telesampler console. He was trembling with eagerness as he tuned the circuitry and trained the gun unit toward the whizzing colored disks in the distance.

The Spanish coast was already in view. Bud could make out a clustered glow of lights from the direction of San Sebastian and guessed that some sort of festival event must be taking place at the famous seaside resort. But the brilliance of the UFO's far outshone the lights below.

Wolf, Sandy, Phyl, and Dr. Feng had all gathered in the cockpit. As word was passed over the intercom, Chow too scrambled forward to crowd into the flight compartment.

"They must be spacecraft-with intelligent beings operating them!" Phyl declared as she gazed wide-eyed at the streaking objects. "Look how they stay in perfect formation!"

Second by second, the plane was drawing closer to the disks. Bud tensed at the controls, keeping the Queen's nose aimed straight at the weird aerial armada. He was determined not to alter course until the last possible second.

Feng had been conning the objects intently through binoculars. But he could make out little except the general shape of the disks. "Their light is too dazzling," he reported, "and they are moving too-"

He broke off in surprise as the UFO's suddenly zoomed up and away!

"They're trying to avoid us!" Sandy cried out.

Bud gunned the atomic jets. The Queen lunged forward, like a sky hound straining at its leash. Soon the Mach meter was swinging well past Mach 4. But even this blinding speed was not enough - the red, blue, and yellow disks were easily pulling away from their pursuer!

Bud groaned in disappointment. "No use! We can't catch 'em!" The UFO's were dwindling from view in the night sky and soon disappeared altogether, zooming high out over the Atlantic.

"They were spaceships, all right," Bud said as he circled back toward the coast. "They have to be! No aircraft could move that fast!"

Presently Tom climbed up into the cockpit.

"Did you find out what they're made of, skipper?" Bud asked. His eager smile faded as he saw the expression on his pal's face.

"I got nothing," Tom replied. "No sample - not even an analysis on the readout."

"How come? Wasn't the telesampler working?"

"Sure, working fine. I checked it out."

Dr. Feng stared at the young inventor. "But - what does this mean?" He faltered.

"Just one thing, as far as I can see," Tom replied. "The UFO's are not material objects."

His words drew startled gasps. "Great bellowin' longhorns!" Chow burst out. "Boss, are you sayin' them things are jest-jest sky spooks?"

Tom shrugged. "Call 'em that if you like, pardner. All I know is, they don't seem to be made of matter. Maybe they're just an hallucination, as some people have claimed."

"If you mean we were just imagining those colored disks, I don't believe it!" Sandy retorted. "We all saw them!"

"Well, there's one way to find out," Tom said. "Let's see if they show up on the videotape."

He summoned Slim Davis to take the controls. Then Tom removed the tape from the TV camera and the others accompanied him to the lab compartment to watch as it was played back.

The UFO's showed perfectly on the viewing screen in full color!

"See? What did I tell you!" Sandy exclaimed. "Even the camera saw them - and you certainly can't say it was having hallucinations!"

Phyl giggled. "You should have taped them on your 3-D telejector, Tom. Then you could project your own UFO display!"

She was referring to a three-dimensional television system which Tom had recently invented. A startled look came over his face.

"Good night, Phyl! I think you've hit it!"

"Hit what?"

"The answer. Those UFO's must be three-dimensional light images, like my telejector creates!"

Everyone stared at Tom in astonishment.

"Don't you see?" He went on. "That's the one explanation that covers everything! It explains why we see them and the camera sees them - because they're composed of light impulses-yet the telesampler detects nothing because there's no material substance for it to act on."

"Assuming you are right, Tom," put in Dr. Feng thoughtfully, "what could possibly be causing these light impulses?"

The young inventor frowned and paced about the lab. "They're certainly under some form of intelligent control. Yet I feel sure no one else has been able to copy my 3-D telejector - so if you want a guess, I'd say that some source in outer space may be projecting them into our skies, maybe by laser beam."

"But why?" Bud asked.

"Perhaps in an attempt to communicate with us," Tom conjectured. "And if the UFO's are transmitted by laser beam, that might also explain why they were drawn away from us-maybe to save us from harm if we intercepted the beam."

Dr. Feng was intrigued by Tom's theory. "Your idea of using light for interplanetary communication is rather startling-yet why not? It is largely a historical accident that scientists here on earth mastered the use of radio waves long before discovering the laser. Is it not possible that beings on another planet might have discovered the laser before radio waves? That would put them far ahead of us in perfecting its use."

Tom reported their UFO chase to the Air Force general. Then the Sky Queen returned to its base near Heidelberg so that Dr. Feng could deposit the alchemical volumes safely in his living quarters.

Tom, Bud, Wolf, and the two girls accompanied the professor by taxi to his lodgings with the bag of ancient books. Dr. Feng's landlady handed him a letter which had arrived over the weekend. The envelope bore a Swiss stamp and a red sticker with the word Express.

Feng stood in front of the fireplace as he slit open the letter. "Ah! It is from my old friend, Konrad Tschudi, at Zurich. You have heard of him perhaps, Tom?"

"I certainly have," Tom replied. "Dr. Tschudi's one of the world's greatest astronomers - and a leading expert on comets."

Feng nodded as he scanned the letter. "I wrote him from Philadelphia that you would be coming to Germany. He says he would be happy to show you around Switzerland's observatories if you are able to visit his country."

"That's certainly kind of him," Tom said, "but I'm not sure I'll have time."

Feng glanced at the young inventor with a thoughtful frown. "I suspect he is interested in talking to you about your comet probe. . . . You know, Tom, Tschudi would make a most valuable addition to your scientific crew."

"Hmm. Just what I was thinking. But would he be willing to undertake a space flight?"

"I am sure he would leap at the chance," Dr. Feng replied. "He is a skilled mountain climber - in excellent physical condition - and has always been adventurously inclined."

"Then I'd be glad to have him on the probe team," Tom said. "I'll talk to Dad about it."

The group enjoyed a delicious late supper at a restaurant in Heidelberg. Bud, who declared he was "hungry as a horse," stuffed himself ravenously on soup garnished with dumplings; spicy meat patties called Maultaschen; and a cheese dish laced with oil, vinegar, and onions which Wolf said was called Handkds mit Musik. The husky young flier finished his meal with a huge slice of cherry whipped-cream tone.

"Good grief!" Murmured Sandy, watching in horror. "I hope you know what you're doing!"

"So do I," Bud said with a queasy grin. "Anyhow, it was great while it lasted."

Tom, Bud, and the girls left Dr. Feng and Wolf in town, with a promise from Tom that the Porsche would be flown back from Schloss Enz-bach the next day. Then the teenagers returned to the Sky Queen. Chow, who was waiting up for them like a fat, fussy mother hen, had brewed some soothing hot cocoa - but Bud declined with a groan. "Ugh! Take it away!"

The others retired to their quarters. Tom went to the radio compartment to give his father a full report of the day's exciting activities. He was just signing off when he heard a loud crash over the wall intercom.

"Good night! What was that?" Tom wondered. Then he recalled that Bud had spoken to him over the intercom before he contacted Shopton. No doubt the switch had been left on.

Alarmed, Tom dashed back to the bunk compartment which he shared with his copilot. Bud, looking dizzy and sheepish at the same time, was just picking himself off the deck. "Whew! I fell out of bed!" He mumbled.

Tom suppressed a grin. "What's the matter, pal? Eat too much of that Handkds mit Musik!"

"Too much everything." Bud rubbed one hand over his forehead and the other over his midsection. "Boy, what a nightmare I was having! I dreamed we were back in that alchemists' cave and a bunch of eight-foot-tall Brungarians were coming at us with clubs and battle-axes!"

Tom started to laugh, then suddenly stopped. "Oh, oh! Now you've got me worried," he said.

"How come?"

"When we got that UFO alert, we flew off and left the cave unguarded. Suppose that creep who pushed the boulder at us was hanging around. If he saw us find the cave, he might go back and loot it!"

Bud's sick-to-the-stomach expression faded instantly. "Jumpin' jets! We'd better go see! We might even be able to nab the guy!"

Tom nodded. "Get with it, fly-boy! I'll go warm up the engine!"

Soon the Sky Queen was soaring through the night sky. As they neared the Berg der Weissen Konigin, Tom cut the main jets and drifted in close on the repelatron lifters.

A glow of light was coming from the cave entrance!

CHAPTER XV

TOTTERING TOWER

TOM's muscles tensed as he saw the light from the cave. His hunch about their mysterious enemy seemed to be checking out!

Bud spoke up, "I'm going down with you!"" Okay. Slim, you take over in the cockpit. "As the crew chief obeyed, the two boys ran aft to the main hatch. Chow Winkler waddled along behind them." I'm comin' too, boss!"

A ladder was dropped and the three climbed down. Tom led the way as they crept softly into the tunnel. Moments later, they reached the entrance to the alchemists' cavern.

The light was coming from an electric lantern on one of the wooden tables. A man was pawing through the books and scrolls on the shelves! Hearing a faint scrunch of gravel, he jerked around. His crooked-nose face gaped in panic. "Git him!" Chow yelled.

The man darted across the cavern. With a sweep of his hand, he snatched a heavy earthenware pestle and hurled it through the air.

Tom ducked, but the pestle grazed his forehead. Bud and Chow clutched him anxiously. "Never mind me! I'm not hurt!" Tom said, pulling free.

The momentary delay had given the man a lead. He was running deeper into the cavern, taking the left-hand fork. The trio plunged after him, beaming flashlights, but the man was soon lost to view in the curving passageway. The sound of his footsteps faded.

Minutes later Tom, Bud, and Chow felt a draft of fresh air. The passageway ended and they emerged onto the open hillside after pushing out through a heavy clump of underbrush. Their quarry was nowhere in sight.

"Of all the rotten luck!" Bud blurted angrily.

"Hush up!" Chow waved for silence, but no sound betrayed the position of their quarry.

Tom flicked on his pencil transceiver and radioed the Queen to sweep the terrain with its searchlight. Chow managed to pick up the man's trail. The trio followed for some distance, but the going was slow and when the woods became thicker on the hillside, they finally gave up the pursuit.

The young inventor ordered Slim Davis to keep flying around the hill and try to spot the man with the Flying Lab's search beam. Meanwhile, Tom, Bud, and Chow returned to the cavern.

Tom examined the lantern, then pointed grimly to a Brungarian manufacturer's marking. "Well, at least we know the fellow's nationality!"

"What do we do now, skipper?" Bud asked.

Tom hesitated. "There's always a chance he might come back. I think we should keep watch here till morning - if you two are game?"

Bud and Chow both declared themselves willing.

"Okay. First, we'd better find out where that right-hand fork of the passage leads."

Leaving Chow on guard in the main cavern, the two boys explored the other branch of the rear passageway. It ended in a blank wall of rock.

The trio divided the remaining night hours into watches-one man sleeping while the others stood guard at the two exits. The Sky Queen found a landing spot on a nearby plateau.

When morning came, Tom flew to Schloss Enzbach. He arranged with the count to post watchmen at the cavern until the proper authorities could take charge. Then the Queen returned to Heidelberg, with the atomicar and Porsche aboard.

Tom and Bud found Dr. Feng at the Institute of Physics, at work on the ancient volumes retrieved from the cavern. The books were being carefully dried out. Then, leaf by leaf, the pages were being separated and photographed.

"They are in a remarkable state of preservation," Feng reported. "I suspect we shall find some hygroscopic agent in the cavern, placed there by the alchemists to absorb the dampness."

"Any references to the UFO's?" Tom asked.

"Yes, several. But weeks and days of study may be needed to glean the full facts."

The professor was startled to hear of the intruder in the cave. "What did this fellow look like?" He inquired anxiously.

"Medium height, brown hair, a crooked nose." Tom saw the professor's eyes suddenly widen and inquired, "Does that mean anything to you?"

Dr. Feng frowned and tugged his goatee. "Yes. A most disturbing incident happened this morning." He explained that before leaving his rooms, he had telephoned Dr. Tschudi in Switzerland. "Then I glanced toward the window. A man was peering in, but he darted out of sight immediately. He, too, had a crooked nose."

Tom felt certain the snooping prowler was the same man they had surprised at the cave. He probably had had a car hidden near the hill and had driven to Heidelberg during the night.

Rather than wait in Germany for the results of Dr. Feng's study of the alchemy books, Tom decided to fly back to Shopton. He and Bud slept most of the way, with Slim Davis piloting the Flying Lab across the Atlantic.

Tuesday morning at Enterprises Tom learned that his Mark III telesampler was rapidly nearing completion. News of his rescue of Billy Fox had aroused great interest in Tom's new invention.

"The news agencies have all been clamoring for a demonstration," Mr. Swift told Tom, "so Harlan and I have set up a press conference for Friday. Can you handle it?"

Tom thought for a moment, then nodded. "Sure. Bud and I can put on a show for them."

Mr. Swift said he had passed along Tom's request to include Dr. Tschudi in his comet probe crew. The space agency had agreed, pending a security check on the Swiss astronomer.

Friday morning a group of newsmen gathered in the observatory dome at Enterprises. Tom invited them to look through a small optical telescope trained on downtown Shopton.

The reporters saw the framework of a new twenty-story office building which was going up in the business district. Its steel skeleton rose above the town's modest skyline. Ten parabolic reflectors had been mounted at various points on the girders-one for each newsman.

"You'll each have a chance to put some unknown substance in one of the reflectors," Tom said. "Or a workman will do it for you. Later, I'll try to identify each substance with my telesampler."

By noon the demonstration was ready to proceed. After one of Chow's tasty steak luncheons Tom, Bud, Arv Hanson, and two other crewmen took the reporters aloft in the Sky Queen. Bud and Arv piloted the ship while Tom addressed the newsmen in the plane's passenger lounge.

"I'm afraid there's only room for myself in the blister," Tom said. "But there'll be two-way communication over the intercom, and a crewman will bring each sample up to the lounge."

The Flying Lab hovered low outside of Shop-ton as Tom took his place in the blister. He aimed the gun unit at the reflector designated "A."

Moments later the reporters heard his voice: "Target Alpha-assigned to Mr. Jeff Neimark of Acme Press. The substance is axle grease!"

"Bull's-eye! Give that boy a silver dollar!" Neimark called back jokingly.

Targets B and C were quickly sampled - a piece of leather and a small block of metal alloy. Tom gave the exact formula for the latter, which included a trace of beryllium.

The next target gave Tom more trouble. "It's some sort of fruity substance. I may have to taste it. ... Hmm. Apple butter!"

The reporters laughed and applauded.

The test was proceeding when Tom's face suddenly blanched with horror. Several girders of the small skyscraper were slowly buckling. The whole top section of the structure was teetering dangerously to one side!

"Skipper! You must have damaged the tower!" Bud yelled over the intercom.

Tom scrambled up the ladder to the cockpit, his mind working frantically. The skyscraper section had collapsed still farther.

"The top's going to break off!" Arv predicted.

"Good night!" Bud gasped. "People in the street may be killed if it falls!"

"Quick! Fly over it!" Tom ordered. "I'll rig Dad's giant magnet!" This invention of Tom Sr. 'S, capable of lifting enormous loads, was part of the Sky Queen's regular equipment.

As the plane streaked toward downtown Shop-ton, Tom and the two crewmen lowered the magnet through the belly hatch. Crowds of people were gawking from the streets as policemen sought to hold them back and divert traffic. Squad cars raced to the scene, sirens screaming.

There was a loud creak of metal as the tower sagged still more! In the nick of time, Tom grappled the broken structure with the giant magnet. As the magnet cables were payed out on a winch, the section was lowered to the street.

In the cockpit, Bud heaved a gasp of relief as he said to Arv, "Whew! My heart's still pounding!"

"Yours and mine both, fly-boy!"

The Queen was hovering directly over the street, almost brushing the rooftops with its wings. Bud glanced down. A man was sticking his head out of a top-floor window of a building adjoining the skyscraper skeleton. His eyes met Bud's just as his lips curved in an evil grin.

Something stirred in Bud's memory. He had seen the man's face before at the UFO club meeting! The man seemed to sense Bud's recognition. He ducked back and slammed down the window.

"Arv, take over!" Bud cried out. "When the cable's hauled in, skim over that building!"

Unfastening his seat belt, the young pilot dashed below to the belly compartment and explained his suspicions to Tom. "I've a hunch that guy may be Bascum!" Bud declared.

A ladder was lowered and Bud clambered down to the roof of the building. He ran to the stairwell door, opened it, and plunged down the steps. Halfway down, he came face to face with the man he had seen at the window!

"I was just looking for you-Mr. Bascum!"

The man whipped out a device with a tube at one end and a rubber bulb at the other. Before Bud could stop him, he squeezed the bulb.

Bud's face went strangely blank. The next instant he tumbled headlong down the stairs!

CHAPTER XVI

ROOF CHASE

AS the man dragged Bud's limp form from the stairway, the Sky Queen remained hovering near the damaged skyscraper. Tom decided not to airlift the broken girder section for fear some of the structural steel might break loose.

"Contact Hank Sterling," he told Arv over the intercom. "Tell him to bring an emergency crew with trucks and start dismantling the girders."

"Roger!" Arv acknowledged.

Tom also spoke to the newsmen. "It may be a while before we land, but you can file your eyewitness reports from the radio compartment."

As he finished speaking, Tom glanced through a porthole. He saw the stairwell door open on the roof of the building. A man stepped out and glanced up at the Flying Lab. He had wavy dark hair, a bulldog jaw, and massive shoulders.

One look sent a shock of recognition through Tom. He had seen that same face gazing up at him from the UFO club audience! "The guy Bud went after!" Tom realized. But where was Bud?

The man darted across the roof. Tom shouted, "Arv, swing over to that building again!"

As the Queen veered in response, Tom rushed to the belly hatch. The nylon ladder was still dangling. Tom scrambled down it and yelled, "Hold it, mister! I want to talk to you!"

Instead of answering, the man clambered over a projecting wall and fled across the roof of the adjoining building. Tom shouted up to the crewmen at the hatch: "Tell Arv to follow him!"

The Queen promptly glided in pursuit. The man was already vaulting to the roof of a third building - the last in the block. Evidently he was heading for a fire escape. Tom clung to the swaying ladder and waited until he was almost over the fugitive. Then he leaped!

Whoomp! Tom landed astride the man's back, knocking him off his feet. They went down in a tangle of arms and legs.

The man dug his elbow hard into Tom's midriff, then squirmed around, trying to seize the young inventor by the neck. Tom aimed a short, chopping punch at the man's head, followed by a roundhouse right. His opponent's powerful fingers closed on Tom's throat.

By now they had rolled to the edge of the roof. The young inventor fought savagely, but the man's hands were clamping Tom's windpipe, shutting off his air. As they grappled, Tom found himself staring straight down to the pavement, stories below!

Tom felt himself blacking out. Then other hands seized both fighters and dragged them back from the brink. The crewmen and two reporters had swarmed down the ladder to join the fray. In a few moments they subdued the wavy-haired man.

One of the newsmen helped Tom to his feet. "Th-th-thanks," Tom stammered weakly, then added with a grin, "Never let it be said we hold dull press receptions at Enterprises I"

It was evening when Bud finally regained consciousness. He was in a room at Swift Enterprises infirmary. Tom was at his bedside.

"How're you feeling, fly-boy?"

"In one piece, at least." Bud rubbed his hand over his face and sat up. "How did I get here?"

Tom related his own struggle with the wavy-haired man, then went on, "The police searched his office and found you inside. Apparently he'd doped you with some sort of anesthetic."

Bud nodded. "He squirted a gas gun at me. Guess I took a nose dive."

"You wound up with some bruises, but Doc says nothing serious." Tom surmised that the wavy-haired man had panicked when Bud recognized him and had tried to escape via the roof, fearing Bud would immediately summon the police.

"Who is the creep?" Bud asked.

"His driver's license showed the name J. Hup-man, but the FBI has already identified him as a Brungarian agent named Kursov. He rented an office here in Shopton two months ago-probably to spy on Enterprises and maybe eliminate me. He won't talk, but I'm sure he was 'Bascum.'"

Bud blurted, "I'll bet he had something to do with the skyscraper accident, too!"

Tom shook his head. "No, that was an inside job. Someone monkeyed with the telesampler." He explained that once the device had been turned on, the laser had kept pulsing continuously-scoring deep burns through the girders.

Bud gave a rueful chuckle. "Those reporters will be nicknaming your invention the Electronic Termitel. . . I'm sure glad no one got hurt."

There was a knock on the door, and Mr. Swift came into the room. "Well! Glad to see you sitting up, Bud. No aftereffects, I hope?"

"Guess not. My appetite feels about normal."

Mr. Swift's eyes twinkled sympathetically. "You two have had a rough afternoon. I think it's time for some good news."

"What's up, Dad?" Tom inquired.

"Do you recall that comet I sighted?"

"You bet! What's the latest on it?"

The elder scientist said he had been keeping the comet under constant observation. Other astronomers had also begun watching it when it became visible through conventional telescopes.

"The comet has grown much more brilliant," Mr. Swift related. "Based on orbital calculations, it should pass very close to earth - in fact, its tail may sweep through our atmosphere."

Tom's eyes blazed with excitement. "Dad! That must be the comet Dr. Feng predicted - the one recorded by the old Chinese astronomers!"

His father nodded. "Yes, I feel sure it is. I've contacted the space agency and suggested that this comet be the target for your probe."

Both boys were thrilled by the news. Bud jumped out of bed, pulled on his clothes, and insisted on going along to the observatory.

The megascope's drive mechanism was already in operation, keeping the huge device aimed at its target. Mr. Swift turned on the prober circuitry and adjusted the tuning. Presently the comet appeared on the viewing screen.

Bud gaped in amazement at the spectacular space wanderer. "How big is it?" He asked.

"The tail is fifty million miles long and the coma, or head, perhaps a hundred and fifty thousand miles in diameter - but both will grow bigger and brighter as the comet nears the sun."

Mr. Swift focused the prober on the fuzzy, halo-like coma. At its center could be seen a brilliant speck - the nucleus-which he estimated to be thirty or forty miles in diameter.

Mr. Swift told Bud that a comet's nucleus was believed to be made of frozen gases embedded with meteoritic particles - "dirty ice," as one famous astronomer dubbed it.

"In the outer reaches of the solar system," he went on, "that dirty ice is all there is to a comet. Not until it rounds close to the sun does it begin to glow and vaporize and expand. Then the pressure of the sun's light rays and the 'solar wind' of charged particles cause some of the glowing vapor to fan out in a long tail. Afterward, as the comet leaves the sun, it shrinks back to a frozen lump again."

"Dad, we'll have to move fast in order to be ready if the space agency gives the go-ahead!" Tom declared excitedly. "The Mark III tele-sampler was finished yesterday. Bud and I had better give it a full-scale test tomorrow!"

Early Saturday morning the boys flew to Fearing Island, the Swifts' rocket base off the Atlantic coast. Tom's mighty spaceship, the Challenger, had been readied during the night for take-off. The huge, gleaming craft was in the shape of a cube, enclosed within circular rails. These served as tracks for the repelatron dishes.

The telesampler turret had been mounted on one rail, in view of the cabin window. Taller than a man, it was a diamond-shaped structure with gun tubes protruding from three of its faces.

"How about the control console?" Bud asked.

"That's inside the ship," Tom replied, "and so are the recovery tanks for the gun units."

The young astronauts and their three-man crew climbed aboard the Challenger. Soon Tom received the all-clear from launch control. With a surge of power from its repelatrons, the great silver craft soared into the sky.

As they entered the blue-black void of space, the earth dwindled below them to a wrinkled, colored globe, veiled with filmy cloud layers.

The Swifts' space station - a glittering, twelve-spoked wheel came into view. Tom had radioed for a target to be mounted on the hub.

"Space Outpost to Challenger," came the voice of Ken Horton, the station commander. "Ready for the test!"

"Understood," Tom said. "We are proceeding."

He twirled two knobs to aim the Number One gun unit, designed for the shortest operating ranges. Gradually the target - a square of bright metal - was brought under the cross hairs on the gunsight monitor screen. An automatic tracking device would now keep the unit aimed.

Then Tom tuned the telesampler. A red light flashed on the readout panel, and a few moments later he scooped some metallic particles out of the recovery tank with his fingers.

"It's aluminum, Ken!" Tom reported.

"Roger!"

For the next test, the Challenger soared to a higher orbit, commanding a distant view of the phantom satellite Nestria. This asteroid had been moved into earth's gravitational field by the Swifts' space friends. Tom had led an expedition there and planted a permanent base.

At Tom's orders, the base crew had painted a huge white circle and bull's-eye on an open plain of the asteroid. A sample was to be extracted from ten feet below the surface. The test was carried out perfectly with the Number Two unit.

"Lunite ore!" Tom radioed.

For the final test, the Challenger circled to the night side of earth. Tom trained the longest-range gun unit on a crater of the moon. Again the red light flashed on the readout panel as the microwave beam-traveling at the speed of light - probed its target and was reflected back. The analysis clearly indicated that the mineral particles in the recovery tank were of lunar origin.

"Nice going, skipper!" Bud said. "Looks as though you're ready to take on Comet Swift!"

Jubilant at the success of the tests, the boys returned to earth and landed at Fearing Island. Then they flew back to Enterprises and hurried to the Main Building to report to Mr. Swift.

Tom's elation faded when his father handed him a Saturday evening edition of the Shopton Bulletin. Black headlines announced: BRUNGARIA ACCUSES SWIFTS OF DEVELOPING MILITARY DEATH RAY!

Tom and Bud read the news story. The charge was based on the damage caused to the skyscraper during Tom's demonstration of his airborne tele-sampler. A Brungarian spokesman claimed the device was actually a deadly ray gun capable of killing thousands at a single sweep. The Swifts, he said, planned to turn out large numbers of the device for the United States Air Force.

"Dad, this is crazy!" Tom blurted. "I never heard such utter bilge!"

Mr. Swift replied gloomily, "Naturally I've issued a complete denial, but it's a question how many people will believe-"

He broke off as the telephone rang. Tom scooped it off the hook and answered. Mungo Drake, the space agency director, was calling from Washington. "I'm afraid this death-ray story has thrown a monkey wrench into all our plans, Tom," he said. "The State Department's unwilling to risk any further trouble with Brungaria - so we've been forced to cancel your comet probe."

CHAPTER XVII

HONG KONG REPORT

DRAKE'S announcement left Tom stunned. "That news story is ridiculous!" The young inventor protested. "I can prove to any scientist that my telesampler's no death-ray weapon!"

"I'm afraid the damage is done, Tom," the space director replied. "Even if you gave out the plans of your device, the Brungarians would call it a cover-up. They'd say you were holding back some deadlier military version. The State Department insists on letting things cool off before we risk any further clash."

Tom's face was dejected as he hung up. Both Mr. Swift and Bud tried to console him. "The picture will be different six months or a year from now," the elder scientist said. "You'll have ample chance to carry out your probe."

"By then Comet Swift will be gone, Dad," Tom said glumly. "There may not be another like it in our lifetime."

The young inventor's mood was no more cheerful the next morning as he sat in the Swifts' living room, reading the Sunday paper. The Bulletin's feature section carried a lurid story on the spectacular comet soon to sweep across earth's sky. The article was full of excited guessing on whether or not this could be the Brungarians' artificial comet. Tom scoffed angrily as he read snatches of the story to his mother.

"Would it be possible to make an artificial comet, Tom?" Mrs. Swift asked.

"On a small scale, yes. Quite a lot might be done along those lines. For instance, experimental models of a frozen comet nucleus could be tried out in the big vacuum tanks used for testing space instrumentation. Then, later on, a small nucleus could be launched by rocket. But I'm positive the Brungarians have no way of creating anything like Comet Swift."

Sandy and Phyl came into the room. "All right-wipe that gloomy look off your face!" Sandy said with a giggle to her brother. "We've come to take you for a ride on a comet!"

Tom smiled wryly. "Thanks, but I'm not sure I feel up to it today."

"Think we're joking?" Phyl asked.

"I don't see any comets parked outside."

"Maybe you haven't looked in the right place," Sandy retorted mischievously. "Come on, Phyl! Let's pry him out of that chair!"

The girls seized Tom's arms and pulled him to his feet. With a parting wink at his mother, Tom accompanied them outside. In the back yard he stopped short with a gasp.

A small, comet-like object with a fluttering yellow tail was hovering overhead! Bud's head protruded above the round enclosure at the front. Tom burst into howls of laughter.

"Comet Barclay! Come on down, you nut, before the Air Force orders a jet scramble!"

Bud swooped neatly into the yard on his queer craft. It was a repelatron flying carpet built up with papier-mache and yellow tissue-paper streamers. "What do you think of our artificial comet, genius boy?" Bud demanded.

"I think the Brungarians'll be after you next - if the men in white don't get you first!"

"Don't knock it till you've tried it, pal. You're about to become our first passenger."

"And get your swim trunks," Sandy added merrily, "because we're going to the beach!"

"On this kookie contraption?" Tom laughed again. "We'll have the place in a panic!"

Nevertheless, he got his trunks and joined in the outing good-naturedly. The girls had packed a picnic basket. The four teenagers swam, lunched, and sunned themselves on the sand. By the time they returned home in the evening, Tom had regained his usual cheerful high spirits.

Next morning at Enterprises the young inventor received a videophone call from Germany. He had arranged for Dubois, the Swifts' European telecaster, to fly to Heidelberg and stand by to transmit immediately any findings by Dr. Feng.

The professor's face was excited as he came on the screen. "I have found a passage in one of the manuscripts which definitely refers to the UFO's, Tom. But the meaning is not clear."

"What does it say?" Tom asked eagerly.

"That the alchemists received 'messengers of light' from worlds beyond earth - and communicated back by the power of the White Queen."

Tom racked his brain intently. "One thing's clear, at least," he told Dr. Feng. "The UFO's must be a way of signaling earth-probably from beyond our solar system, since our space friends know nothing about them."

After discussing the puzzling passage with Tom, Dr. Feng went on, "I have also some information about that Brungarian expedition to Mongolia."

"Great! How did you find out?"

"Through a friend at the University of Hong Kong, who recently talked to some visiting scientists from Red China. He learned that the expedition went to an ancient observatory site to unearth old Chinese astronomical records."

Tom felt a thrill of excitement. "That could mean they found out about the spectacular comet you predicted was due to return - the one now approaching the sun!"

The professor nodded. "Yes, Tom. The same thought occurred to me."

As soon as he signed off, Tom rushed to the Swifts' office. "Dad, this practically proves the artificial comet story is phony! I'll bet the Brungarians spread those rumors themselves!"

"How do you deduce that, son?"

"It's typical of the way they operate! Don't you see? From the old Chinese records, they must have calculated that a vivid comet would soon reappear. So they began dropping hints about an artificial comet project. Once that comet becomes visible to the naked eye, people on every continent will be impressed! They'll call Brungaria the world's master space power!"

Mr. Swift was startled. "Your theory certainly makes sense, Tom." He rose from his chair to pace about the office. "The scheme has another advantage, too. By warning against any probe of the comet, they found a way to block your project and keep the United States from gaining more scientific prestige. I think we should notify the space agency about this!"

Tom put through a call to Washington at once. "I agree this puts a new light on the situation," Mungo Drake said. "Maybe we can change the State Department's mind."

The Swifts waited tensely throughout the afternoon. Shortly before five o 'clock, Drake phoned back. "We've decided to call the Brungarians' bluff, Tom. Your comet probe has been okayed!"

"That's terrific news!"

"How soon do you think you can take off, Tom?" The space director queried.

"Before the end of this week, if possible. Next Monday at the latest."

Tom spent the evening plunging into a welter of preparations for the space voyage. Security clearance for Dr. Tschudi was received the next day. Mr. Swift cabled the Swiss astronomer at once.

Dr. Tschudi, a tall, dark man with a trim beard, arrived late on Thursday. Tom took time Friday morning to show him around the Fearing Island base and brief him on the Challenger.

"Marc Bolen will go over the instrumentation with you," Tom said. "There'll be a micrometeoroid detector to check the distribution and velocities of the dust particles in the coma and tail; a magnetometer for studying the interaction of the comet gases with the solar wind; and of course spectroscopic and photometric equipment for UV and IR studies of the structure of the nucleus."

"I look forward to meeting Mr. Bolen - and to my first flight into those regions which I have so far only glimpsed through a telescope."

Tom grinned. "You're going to be the fastest-trained astronaut in history, Doctor. But I don't think you'll find the going too rough in the Challenger."

Twenty-four hours later the great spaceship took off on its daring comet cruise. Besides Tom, Bolen, Tschudi, and two other scientists, the probe crew included Bud, Arv Hanson, Chow, and three regular space crewmen.

Tom had programmed the repelatrons to maintain a constant 1-G thrust. Under this smooth acceleration, the ship rose from earth with no shock of take-off. Yet by the time it reached the halfway point to the comet, the Challenger would be zooming through space at enormous velocity. Then it would decelerate at the same rate.

They had just climbed beyond the Van Allen belt when Ames's voice crackled over the radio: "Enterprises to Challenger! Can you read me?"

"Loud and clear, Harlan," Tom responded. "What's the good word?"

"It's not good, skipper. Kursov has finally talked. He says the Brungarians are going all out to sabotage your comet probe. He doesn't know what they're planning, but he's sure the Challenger is heading into deadly trouble!"

Before Tom could reply, Bud shouted in alarm, "Tom, look! They're coming straight at us!"

CHAPTER XVIII

MESSENGERS OF LIGHT

TOM glanced around as Bud tugged his arm. A formation of UFO's was zooming toward the ship!

Tom gasped. "Stand by, Harlan! We have company up here-UFO's!" As he spoke, Tom switched on the probe's television and motion-picture cameras.

The colored disks veered suddenly and began maneuvering in full view of the cabin window.

"They're sure not avoiding us this time!" Bud declared excitedly.

By now the Challenger was streaking through space at thousands of miles per hour and increasing speed every instant, yet the UFO's appeared to keep a constant distance from the ship. Tom and Bud watched spellbound as the dazzling shapes swooped and circled back and forth. Others in the crew crowded into the compartment to observe the brilliant display.

"Brand my stewpot if them sky spooks ain't puttin' on a show jest fer us!" Chow muttered.

"You're right, Chow - that's exactly what they're doing!" Tom said tensely.

"You still think beings outside the solar system are signaling to us this way?" Bud asked.

"I'm sure of it," Tom replied. "What's more, I've a hunch the message may be urgent."

To double-check, Tom probed the UFO's with his space telesampler. Again the readout gave no analysis, and no particles were obtained.

At last the whizzing disks shot away, zooming off into the inky darkness of the space void.

Tom snatched up the microphone again and reported what had happened.

"Could be their purpose is to warn you about an ambush in deep space!" Ames radioed. "I think you should turn back, skipper!"

Mr. Swift's voice came in. "Harlan's right. There may be a plot to destroy your ship!"

Tom's jaw clenched. To turn back now would mean his enemies had won-had succeeded in thwarting his comet probe. All his preparations for the daring space feat would be wasted.

"Dad, I want to go on," Tom pleaded. "Our course is computer-set to intercept the comet before it reaches perihelion at the sun. Think what an achievement that'll be - a milestone in science! If we turn back, the chance is lost!"

"What about the danger, Tom?"

"I'm sure we can ward off any outside attack with our repelatrons."

"Outside attack, maybe," Ames's voice cut in, "but what if Kursov's warning means there's a traitor aboard? Remember, we still haven't discovered the inside saboteur at Enterprises."

"I'm not worried about that, Harlan," Tom replied. "Every man aboard has had a security check. As far as I'm concerned, they're all above suspicion. Look, Dad-suppose I put it up to the crew. If they vote to continue, do we have your permission to go on with the probe?"

There was a tense silence. Then Mr. Swift's voice responded, "Very well. It's agreed."

Tom turned to the others in the flight compartment. "You've heard what was said. Think it over. Then I'll ask for your votes."

First, he summoned the three remaining crew members from other parts of the ship. When they came to the flight compartment, Tom told them the situation, then asked the crew to decide.

"I vote we keep going!" Bud spoke up loyally.

"Same here," said Arv Hanson.

"I, too, feel the same way," Dr. Tschudi said.

One by one, the crew members agreed to go on. The only dissenter was Marc Bolen. "I'm as anxious to carry out this probe as any of you," he said sullenly, "Remember, I worked on the instrumentation. But why risk our necks?"

"Brand my chowder, you heard what Tom said!" Chow growled. "We got our repelatrons ridin' shotgun on this trip. They can ward off anything the Brungarians throw at us. So what're you scared of? Or do you think we got a double-dealin' traitor aboard, like Ames said?"

"No! I never said that!" Bolen reddened.

"Then what's stickin' in your craw?"

Bolen looked at the crew's scornful faces. "I'm not afraid if that's what you're thinking!"

"What else can we think?" Bud retorted.

Bolen said angrily, "I was just trying to be sensible, that's all. If the rest of you don't see it that way, okay. I'll go along!"

Tom said, "Don't let yourself be pressured, Marc. If you think we should turn back, you have a perfect right to say so."

"Forget it!" Bolen snapped. "I said I'd go along and I will - so the vote's unanimous."

Tom gave him a cool look. "All right. Fair enough." He spoke into the microphone: "Dad, the crew's with me, so we're going ahead."

"Understood, son. Good luck!"

After he had signed off, Tom's thoughts went back to the UFO's. Were the mysterious disks indeed "messengers of light"? If so, what were they signaling - a warning of a space ambush?

"That certainly wouldn't explain all the times they appeared back on earth," Tom mused.

Then another idea struck him. Although the UFO's had shown up on videotape, would they also appear on photographic film? "Take over, Bud," Tom said. "I want to look at the motion pictures we got of those disks."

Tom unloaded the reel of film from the camera and hurried to the lab compartment to develop it. In minutes the film was emerging from the automatic processor. Chow waddled into the room to watch as Tom threaded it into a projector.

The young inventor switched off the compartment lights and started the machine.

"Hey! Them things weren't whizzin' around that fast!" Chow exclaimed. The UFO's appeared on the screen as mere blurred light trails.

"No wonder - the projector's running about three times too fast." Tom started to turn the control knob back to normal speed. Then he stopped. Something about the appearance of the light trails had jogged a faint memory in Tom's brain. He stared at the screen.

"What's the matter, boss?" The cook asked.

"Chow, you old spud peeler, I think I've just solved the mystery of the UFO's!"

Hastily Tom opened the photographic locker and loaded film into a miniature camera. Then he reversed the reel in the projector and began running the UFO movies again at the same speed. Aiming the camera at the screen, he snapped pictures of the intricate light trails. When Tom returned to the flight compartment, he was clutching a number of photographic enlargements. Bud saw his friend's excited expression and asked, "What's up, skipper?"

"Take a look at these, Bud!" Tom held out the prints. "Do they remind you of anything?"

Bud scanned the photographs, frowning as he studied the curious patterns formed by the UFO light trails. "No. . . . Wait a second! This one looks familiar somehow, but where did I-"

Bud broke off suddenly, mouth agape. "Jumpin' jets! Doesn't that look like a symbol in those old alchemy books Dr. Feng was showing us?"

"Right! And I'm sure that's how the old White Queen alchemists received their communications from outer space-those lighted disks traced out the symbols in the sky."

"Man alive, why didn't we guess that before!" Bud exclaimed. "And you think the lights are projected from a planet of a star near earth?"

"Sure. Maybe Alpha Centauri or Proxima Centauri. They're nearest."

"But how would the star creatures have learned the alchemical symbols?"

"Good question. Maybe the alchemists marked out the symbols on the hillside, as they did with the mercury symbol-along with pictures or other clues to explain their meaning. Then the star creatures scanned them by laser beam."

"Sounds like a good guess," Bud conceded.

"The important thing right now," Tom went on, "is to get these symbols decoded pronto!"

The young inventor radioed Fearing and asked to be put in touch with his father at Enterprises. Mr. Swift listened in amazement to Tom's report.

"I'll transmit the symbols to earth by telescan, Dad," Tom said. "Then you can relay them by videophone to Dr. Feng in Heidelberg."

"Right, son. I'll alert Dubois immediately!"

It was twenty minutes past midnight when Mr. Swift finally called back. Tom and Bud were again alone in the flight compartment. They had returned to stand the midwatch after being relieved at the controls by Arv and the other crewmen. Suddenly Tom Sr. 'S voice came over the radio. "Enterprises calling Challenger!"

"We read you, Dad!" Tom responded. "Any word from Dr. Feng on those symbols?"

"Yes, son. He worked out a complete translation. The message is a warning, all right - but not of a mere space ambush. It tells of a catastrophe worse than we could have imagined!"

Tom caught a grim note of fear in his father's voice. "What does the message say, Dad?"

"That the approaching comet is deadly dangerous! When it sweeps through earth's atmosphere it will release a poisonous radiation that may wipe out all forms of life!"

CHAPTER XIX

A HAZARDOUS PLAN

THE approaching comet was actually a missile of doom! Tom and Bud were appalled at the news.

"Have you informed our government, Dad?"

"Yes. An urgent meeting of the United Nations is being called for tomorrow. Top scientists of every country are being asked to attend. A crash program of fallout shelters seems to be the only hope - but it's doubtful the world's entire population can be protected."

Tom still felt dazed as he signed off. Bud said, "What's our next move, skipper?"

"I don't know yet. It'll take time to think this out. . . . The Challenger's radiation shield will. . . Will. . ."

Bud glanced sharply at his friend as Tom's voice trailed off. The young inventor's head was drooping and his eyes looked glazed.

"Tom!. . . Tom, are you sick?" Bud sprang up from the copilot's bucket seat to shake his pal. As he did so, his own legs felt rubbery. A wave of giddiness swept over him.

Tom, meanwhile, was making a desperate effort to collect himself. The realization of their peril aroused him like a dash of cold water. "Steady, Bud!" He stood up and grabbed the copilot's arm.

"Wh-what's causing this?" Bud stammered. "Are we in the comet's radiation belt, or have the Brungarians uncorked their sabotage plot?"

"I don't know!" Tom reached out to press the ship's general alarm button. "Something may be wrong with the air supply! We'd better check!"

Leaving the Challenger to pursue its computer course un-conned, the boys put on oxygen masks and took the elevator to the hangar deck. Neither was sure he could keep his feet all the way.

Tom was first to reach the compartment where the air-purification plant was located. The door was ajar. He opened it and lurched inside.

Tom gave a choked cry as he saw an oxygen-masked figure bent over the machinery. "Bolen!"

The black-browed young astrophysicist looked up with a start. He had a wrench in one hand. "Tom! I - I didn't hear you come in."

"I'll bet you didn't!" Tom thought fast. There was no time to parley. His strength might give out at any moment. Summoning all his resources, he hurled himself at Bolen.

For a moment Bolen seemed too startled to resist. He reeled back under Tom's attack, then swung the wrench to defend himself. Tom seized his wrist and they toppled to the deck.

Bolen, too, seemed groggy but he fought hard. They grappled as Tom tried to pinion his arms.

Suddenly Bud's voice cut in. "Let him up, skipper! I have him covered!"

Bud had snatched a portable repelatron from a rack outside the compartment. Tom released his opponent. Bolen looked confused as he struggled to his feet. Then the astrophysicist felt himself being slammed backward. Invisible repulsion rays were pinning him against the bulkhead. Bud had braced himself in the doorway and was aiming the repelatron at him.

"What's wrong with you fellows?" Bolen gasped. "You're treating me like a-like a-"

"Traitor!" Bud snapped. "Sure! It's the right word, isn't it, for any dirty rat who'd try to sabotage the ship's air supply?"

"You're crazy!" Bolen protested. "I wasn't-"

"Pipe down before I squeeze the air out of your lungs with this repelatron beam!"

Tom was working frantically. He valved pure oxygen into the system and speeded up the blowers to flush the air from every compartment.

Then he cut in the emergency purifying equipment to filter out any toxic agents.

Gradually the atmosphere improved. Tom and Bud, who were both close to collapse, revived rapidly as they breathed in the fresh, oxygen-rich air.

By this time most of the crew-startled and still somewhat groggy-were crowding into the compartment. Bud told them what had happened.

"You're wrong!" Bolen insisted desperately. "I didn't sabotage the air supply! I was trying to fix it! I knew something was fouled up, because I was feeling woozy myself!"

"Why didn't you sound the alarm?" Tom asked.

Bolen shrugged helplessly. "I don't know. Just didn't think of it, I guess. I wanted to fix the trouble fast before we all conked out."

"Don't give us that!" Bud jeered. "You fooled us once before when we caught you in Tom's lab with Sam Crivet. That time you threw the blame on Sam - but now we've got you dead to rights!"

Bolen wilted when he saw the furious expressions of the crew. "All right. I'll admit I was the saboteur back at Enterprises, but I swear I never tampered with the Challenger's air sup-ply!"

Bolen confessed that he had started to wreck Tom's space telesampler when Crivet called into the lab. As the technician entered, Bolen had darted behind the door and knocked him out. Before Bolen could complete the sabotage, Crivet had come to, and although still in a daze, had attacked him.

Bolen said he had painted the comet sign on Tom's blotter and had knocked the young inventor unconscious to keep from being discovered. He had also made the maniacal telephone call after Tom's power-line mishap. Later, he had planted a fire bomb on the Sky Queen and tampered with the laser switch before Tom's press demonstration of his airborne telesampler.

"Why, Marc?" Tom asked. "What reason did you have for doing all those things? Haven't we always treated you fairly at Enterprises?"

Bolen hung his head sullenly. "I did it to avenge my father." He explained that Curt Bolen, a physicist at a West Coast atomic plant, had worked for years to design a new type of proton accelerator, only to have his lifework obsoleted when Tom Swift Sr. Perfected the Swift proton accelerator. As a result, the elder Bolen had suffered a nervous breakdown.

"That's why I applied for a job at Enterprises," Bolen went on. "You Swifts probably never even heard of my father's work - but I was determined to make you both pay."

"I suppose you voted to return to earth because it was an easy way to wipe out my whole comet project," Tom said.

Bolen nodded. "Sure. I wasn't afraid of the danger. That's why I changed my vote. I didn't want everyone calling me a coward."

"So you chose another way to get revenge," Arv Hanson growled, "-by tampering with the air supply and disabling the whole probe crew."

Tom was puzzled when they could find no trace of a container from which Bolen might have fed the toxic agent into the air supply. Nevertheless, with appearances so much against the astrophysicist, Tom could not risk his crew's safety. He ordered Bolen confined to a storeroom.

Then Tom told the assembled probe crew about the impending danger to earth from the comet's deadly radiation. "We ourselves will be exposed to the greatest possible intensity if we maintain our course," he said grimly. "I believe the Challenger's shielding will protect us. But it's up to you fellows to decide if you want to face that danger or turn back."

There was a stunned silence. Dick Lamson, one of the probe scientists, spoke up. "If we do return to earth, we'll still be in danger from the fallout - like everyone else-won't we?"

Tom nodded. "Sure. But there's still a chance of survival in a fallout shelter, assuming we're lucky enough to find room somewhere."

Bud said, "Suppose we do keep on, skipper. Have you any kind of plan to save the earth?"

The young inventor paced the deck tensely.

"Yes. I believe it may be possible to divert the comet far enough off course to keep its tail from passing through earth's atmosphere. But I warn you it'll be a hazardous job! If we fail, it could mean lights out for all of us."

Because of their small mass, Tom explained, comets are readily affected by any outside gravitational tug. Even Comet Swift might be deflected by a relatively small "nudge." The ship's repelatrons might achieve this, especially if their effect could be speeded by the directed force of a rocket-fuel explosion.

He sketched out a rocket-thrust device which could be implanted in the comet's nucleus. This would be powered by the entire supply of fuel for the Challenger's auxiliary rockets - in effect, turning the whole comet nucleus into a huge "rocket ship." The reaction effect to the explosion of the rocket fuel, added to the powerful shove of the Challenger '?, Repelatrons, might deflect the comet onto a new course.

Chow blurted, "I ain't sure I savvy all that, boss, but I'm willin' to give it a try!"

The other members of the crew agreed.

Tom immediately activated his plan. Driving themselves with little sleep, the crew worked frantically to fashion the comet "rocket engine" which Tom had devised. The Challenger's machine shop and forge hummed with activity.

As the days passed, they drew constantly closer to their target. Tom checked the radiation monitors frequently and probed the comet nucleus with his telesampler. Its makeup seemed to bear out the predictions of astronomers. Frozen substances such as methane, ammonia, carbon dioxide, and water ice were present, as well as particles of sodium, iron, nickel, and chromium. But all were highly radioactive!

At last they entered the glowing coma. Its eerie light filled the ship. The Challenger zoomed on toward the nucleus. Gently the huge ship touched down on the icy sphere. Tom was concerned as their landing struts sank into the mushy surface, but it appeared firm enough to support the spaceship's weight.

The crew, in anti-radiation space suits, maneuvered a small atomic earth blaster out of the ship to bore a cavity for the rocket-thrust device. When the cavity had cooled sufficiently, a tank lining was installed and fuel was pumped into it from the ship, under extreme precautions. Finally the "rocket engine" was hauled out in pieces and assembled in place with its cluster of rocket tubes.

Tom heaved a sigh. "So far so good," he said over his suit radio. "Now to-"

Another voice interrupted. "Excellent work, you American fools I Now you may ride your comet spaceship into the fiery inferno of the sun's embrace!" It was the voice of Konrad Tschudi, followed by a jeering peal of laughter!

As Tom and his companions stared in horror, the Challenger rose from its landing site and soared upward through the glowing coma!

CHAPTER XX

THE COMET CONQUERORS

MAROONED on a deadly radioactive comet! The astronauts gaped helplessly at their departing spaceship. Tom was first to recover from the paralyzing wave of fear that overwhelmed them.

"The rocket fuel!" He exclaimed. "If Tschudi ignites it, we may be blasted to bits!"

Tom sprang into action. He was sure the renegade astronomer would not dare detonate the thrust device until the Challenger had risen to a safe range. But only seconds remained. With fumbling hands, made clumsy by his space gauntlets, Tom hastily disconnected the radio ignition circuit. Then he paused for breath - clammy with perspiration inside his space suit.

"Fast thinking, skipper!" Bud gripped Tom's shoulder.

"We're still in an awful spot, Bud." Tom saw the others watching him tensely. Where could help come from? No spaceship from earth could rescue them now. The comet would race on toward the caldron of the sun. Any chance of survival under its searing rays was slim indeed - and once the comet had rounded the sun, it would hurtle away, ever farther from earth, into the trackless reaches of space.

"That sneakin' sidewinder Tschudi!" Chow blurted. "I'd like to get my grub hooks on him!"

"He was the Brungarians' secret stooge - not Bolen!" Arv chimed in.

Bolen! Tom was electrified as he thought of the young astrophysicist still locked in the storeroom aboard the Challenger. "Bud! The intercom was still on, wasn't it?" Tom asked.

"Sure, skipper." The intercom system had been turned on while the rocket-thrust device was being unloaded, so the astronauts could talk back and forth on their suit radios to any part of the ship-their voices being picked up from the loudspeaker. "Why?" Bud added.

Instead of answering, Tom said rapidly, "Marc! Marc Bolen! Pull the recessed ring left of the door! It's an emergency release!"

The others held their breath, catching Tom's excitement. They realized now why he had not answered Bud's question. Tom's reply over his suit radio would have been heard by Tschudi.

"Can you read me, Marc?" Tom asked tensely.

There was no response.

"Tschudi's shut off the intercom!" Bud said.

"We'll just have to hope Bolen heard enough of the message to dope out what I meant," Tom said.

"What exactly is that recessed ring you spoke of?" Dick Lamson put in.

"It triggers a CO^2 cartridge that blows out the hinge pins and springs the door open. Every interior hatch is equipped with one. The space crewmen all know about the system, but you scientists were never briefed on it."

There was nothing to do now but wait. All realized their lives depended on Bolen. But even if Tom's call enabled him to get out of the compartment, would he come to their rescue?

The astronauts stared upward anxiously into the glow of the comet's coma-straining their eyes to keep the Challenger in view. The ship had dwindled to a brilliant speck. Only because of the high reflectivity of its polished surface was it still visible through the glowing vapor. At last the speck could no longer be made out.

As moments passed, the stranded spacemen began to lose hope. Then Tom exclaimed, "I see it!"

The speck had reappeared! All eyes watched intently. "It's growing bigger!" Bud yelled. "The ship's coming back!"

"Tom to Challenger!" The young inventor called. "Do you read me?"

A voice responded over the radio: "Bolen here! I read you and everything's under control."

The astronauts broke into shouts of joy!

"Where's Tschudi, Marc?" Tom queried.

"Lying on the deck," Bolen answered. "I had to clout him with a wrench after I got out of the storeroom. He looks as if he's coming to, but I have his wrists tied."

Tom and his men cheered when the Challenger finally landed on the nucleus. Bolen brushed aside their thanks. "I may have had a grudge against you and your father, Tom, but I'm no turncoat. Actually, it was a lucky break for me that I got this chance to redeem myself."

"You've done a lot more than that, Marc," Tom said, "but we'll talk about it later. Right now we have to ditch this comet fast before its tail sweeps through the earth's atmosphere!"

The ignition circuit was reconnected. Then the astronauts soared in the Challenger to a safe distance from the comet's icy core.

"Here goes!" Tom pressed a switch. A blast of fire spewed from the nucleus, amid billowing clouds of smoke! The spacemen saw the nucleus react perceptibly to the tremendous explosion.

Then Tom swiveled the ship's repelatron radiators so that one beam was braced backward against the distant earth while the other was directed toward the comet ball. He gunned the generators to maximum thrust. Slowly the nucleus moved away from them as it changed its course.

"Have we nudged it enough, skipper?" Bud asked.

Tom studied the luminous red image of the comet nucleus on the space-position-finder screen and checked a number of instrument readings. "It's too soon to tell, Bud - but I hope we have. Even the earth must've moved a bit. A small deviation in course now can make an eventual difference of thousands of miles as the comet continues its orbit. Its new path will take it much closer into the sun's gravitational field, which will pull it still farther off course. We'll have to keep our fingers crossed."

Radio reports from earth kept them informed as the well-shielded Challenger cruised homeward through the glowing coma and wide-sweeping tail.

At last Mr. Swift's voice brought the news they had hoped for. "Our satellite monitors show only a relatively light fallout - not enough to endanger any forms of life on earth."

The crew cheered and wrung Tom's hand.

A later report made them roar with laughter. Mr. Swift said Brungaria had been frantically denying it had anything to do with the radioactive comet, or had ever planned to launch any comet. "Their propaganda stunt has backfired. Many people think they were plotting to dominate the earth." He also said the Brungarians denied all knowledge of Tschudi or any sabotage plot.

The prisoner had been kept under constant guard since the Challenger's take-off from the comet nucleus. As they neared earth, his attitude of surly defiance seemed to wilt. Finally he sent for Tom and agreed to tell his whole story in exchange for a lighter punishment.

"I can't make any deal," Tom said brusquely, "but any information you give us should count in your favor. I'll do what I can, of course."

The prisoner nodded. "Very well. That is good enough. I am not Dr. Konrad Tschudi, but a Brungarian agent. My name is Pavlov Riakim."

He revealed that two spies in Germany had been alerted to watch Dr. Feng after Kursov reported the professor's visit to Tom Swift. One was the man with the crooked nose. They had followed Tom's party to Schloss Enzbach, had tried to get rid of the young inventor by pushing the boulder downhill, and had snooped in the alchemists' cave. One had entered the castle at night to glean information about Tom's mission in Germany. Later, the crooked-nosed man had eavesdropped on Feng's telephone call to the real Dr. Tschudi and thus learned that the Swiss astronomer was to take part in the comet probe.

The real Dr. Tschudi, Riakim said, had been kidnapped in Switzerland. Riakim had taken his place, with orders to sabotage Tom's comet probe and if possible take over the Challenger.

Tom radioed the information to Ames at once.

A tremendous ovation awaited the astronauts when they landed on Fearing Island. Officials of the United States Government and numerous foreign countries were on hand to thank Tom Swift and his gallant crew for saving earth from disaster. Tom was called on for a speech and interviewed repeatedly before the television cameras.

Mr. And Mrs. Swift, Sandy, Phyl, and Harlan Ames flew back with the astronauts to Enterprises aboard the Sky Queen. Ames told Tom that from Riakim's information, the Swiss police had been able to rescue Tschudi and arrest his kidnappers. The spy with the crooked nose and his accomplice had been apprehended in Germany.

"That's great, Harlan!" With a sigh of satisfaction, Tom relaxed in his cushioned lounge seat.

"Don't get that faraway look in your eyes," Sandy warned. "Phyl and I are planning to keep you and Bud earthbound for a while!"

Tom grinned. His comet exploit had given him ideas for other daring space projects. In a short time the young inventor would be involved in a thrilling adventure far from earth, The Captive Planetoid.

"Besides," put in Mr. Swift with a smile, "you've an appointment to address the United Nations, Tom, and receive a gold medal."

"Address the UN?" Tom echoed in dismay. Then his grin returned as he looked at Bud and the girls. "Well, maybe. . . But tell them first I have an appointment to take another comet ride - to the beach aboard Comet Barclay!"

THE END

Table of Contents

CHAPTER I DOOM GLOW

CHAPTER II THE FLYING GOAT

CHAPTER III GROUND LIGHTNING!

CHAPTER IV VANISHING FUZZ

CHAPTER V A WHITE-FACED CAPTIVE

CHAPTER VI THE HAWK CLUE

CHAPTER VII PURPLE DUST

CHAPTER VIII MONGOLIAN MYSTERY

CHAPTER IX BOMB BLAZE

CHAPTER X A STARTLING SKYROCKET

CHAPTER XI DEADLY WEAPONS

CHAPTER XII A GHOSTLY KNIGHT

CHAPTER XIII SIGN OF MERCURY

CHAPTER XIV SKY SPOOKS

CHAPTER XV TOTTERING TOWER

CHAPTER XVI ROOF CHASE

CHAPTER XVII HONG KONG REPORT

CHAPTER XVIII MESSENGERS OF LIGHT

CHAPTER XIX A HAZARDOUS PLAN

CHAPTER XX THE COMET CONQUERORS