"Well, for Pete's sake!" Tom muttered to himself.

For an instant he was set to leap up from behind the chair and go after the man. But he was puzzled. He had to find out what made his ornamental desk piece so important.

Gingerly Tom lifted the craft and examined it closely. At first glance there was nothing to indicate Marco carefully set the model on the desk in THE SECRET RECORDER.

99.

that the model had been tampered with, yet something seemed different.

Tom studied it at various angles.

"I know!" he murmured. "The plane's heavier than it was-weighs several ounces more than it did!"

Tom began to manipulate each of the moving parts. He spun the wheels, then turned his attention to the control surfaces. He flipped the model's rudder.

Suddenly the bottom fell out, along with a reel of recording tape.

Dumfounded, Tom s.n.a.t.c.hed up the tiny reel, exactly the same position Tom had left it 100 .

then peered into the model. Within he saw a spindle and a recording head.

Reaching in, he pulled out part of a miniature tape recorder.

"Very clever," he muttered. "An ingenious machine with a built-in amplifier, its own power supply, and a tiny microphone strong enough to pull in a roomful of conversation."

Tom noticed that the degree of miniaturization involved bore a striking resemblance to that used in the mechanical crow.

"The same enemy!" he thought. "But one thing's sure. It can't be Marco. He's a stooge for some brain."

But here at last was the source of the leak! This was how news was getting out! Tom and his a.s.sociates had been broadcasting their most secret plans during their frequent office conferences. Each night Marco probably would change the tape.

The young inventor was sorely tempted to reach in and rip the wiring to shreds. Instead, he sat down and thought over the full implication of the espionage attempt. Then, cautiously, he rewound the tape and set it back in operation.

"Marco must not know I've found out. Before I leave for the Citadel this afternoon, I'll dictate a misleading series of statements about the trip to the West and about the relotrol." Sighing, he continued to speculate, "Since the most recent tape is probably on its way to the enemy, it's a good thing there THE SECRET RECORDER 101.

weren't any secret projects discussed here in the office today."

Right now, Tom decided, it was important that Marco's every move be watched. He slipped from the building without being seen and drove home rapidly. He went at once to the attic where he kept a short-wave radio, used for top-secret communication. Another was set up at Radnor's home.

It was four in the morning when the security officer's sound sleep was shattered by the squeals of the set's speaker. Groggy, he felt for the microphone.

"Wh-what is it?" he mumbled.

"It's Tom. Rad, I've traced the security leak!"

"What!" Radnor was wide awake in an instant. Tom explained what he had learned.

"Great going!" Radnor exclaimed. "Marco leaves the plant in another three hours. I'll have him followed. Security will put one of our night men on the job right away."

When Tom hung up, his troubled mind was relieved. At last the mystery was taking shape. He fell into bed and drifted off into the first peaceful sleep he had had in days.

While Tom slept, Radnor's men began to draw the net around the unsuspecting watchman. A series of check points were set up along the route to Marco's home. His house was placed under immediate surveillance. Less than an hour after Tom's conversation with Radnor, a plant detective was 102 .

posted in the corridor to watch Marco's every move.

When morning came the watchman punched out and left for home. The detective followed as Marco took the expected route, deviating only once, to drop a fat letter in a mailbox.

When Tom arrived at the plant, he went straight to the security office. Radnor was there, studying Marco's personnel record.

"I'm going to double check this information, Tom," he said. "We'll investigate his background again. I'll sift through every one of Marco's acquaintances, in the hope of linking him with the Briggin gang."

"Where do you think you'll start?" Tom asked, thumbing through the reports.

"My first stop is Blackstone," said Radnor, consulting his casebook. "I'll talk to everyone who ever knew Marco at that mental inst.i.tution. Where can I reach you?"

"I plan to leave this afternoon for the Citadel. Everything's ready and I may as well go."

"Then I'll be in touch with you at the atomic energy plant."

Suddenly Tom remembered that he must dictate misinformation into the recorder hidden in the Sky Queen model before he left. When he finished he smiled to himself. The false facts should throw the enemy off, at least for a while.

Phyl and Sandy were on hand early that afternoon, packed and ready for the trip. The repaired Sky THE SECRET RECORDER 103.

Queen, fresh from the plane shops and completely overhauled, was raised from her hangar.

The fuselage gleamed in the sunlight as the great ship was rolled onto a loading ap.r.o.n. The girls went aboard immediately. Then Tom, Bud, Arvid Hanson, and chief patternmaking engineer Hank Sterling, who was going along on the trip, supervised the loading of the cargo.

The first item of importance was Stan Lee, a flat-faced walking robot with which Tom was planning to make experiments in entering and leaving the atomic plant. Next came a drone plane, to be set in motion above the Citadel. Last to be rolled aboard was the squat, angular-looking helicopter, the Skeeter.

When all was in readiness, the girls asked where Chow was.

"At your service," the cook replied, running up in the loudest shirt the onlookers had ever seen.

"Wow!" Bud cried. "You trying to set the plane on fire again?"

Chow grinned and looked down at his bright-red luminous shirt. "Why, brand my Texas general store, I think this here is right purty! But don't you make fun o'

my southwest buyin'. Look what I picked up right in Shopton."

From his bag he pulled out a brilliant gold-and-green plaid shirt. "That's what held me up."

"It would stop anything!" Bud needled.

The travelers waved good-by to their families and 104 .

friends and went aboard. The Sky Queen blasted its exhaust fire at the ground. The silver body quivered and ascended in a direct line until it was ten thousand feet over Shopton. Then Tom cut in the forward power and headed for the West.

CHAPTER 13.

ARV UNDER SUSPICION.

FAR ABOVE the commercial air lanes, Tom set the Sky Queen on automatic pilot, making sure the radarscope and its warning bell were operating, and headed for the atomic energy plant. Cloud formations obscured the earth below, and the pa.s.sengers, comfortably settled in the lounge, began to talk.

"Tom," said Phyl Newton, "please bring me up to date on exactly what your giant robot is going to do-and what experiment Stan Lee will carry on."

The young inventor smiled. He was sure that Sandy, who had a good knowledge of the whole setup, had told her friend a great deal about it. He endeavored to think up phases of the project which Phyl might not have heard.

"As you know, after the atomic pile starts work in its separate concrete shelter," Tom began, "nothing living could survive in there. Even if the pile's 105.

106 .

activities were stopped, and it were emptied of uranium, the radioactivity would kill a man.

"So, until now, repairs on the plant haven't been possible, in case something should go wrong in it."

Phyl interrupted to ask what breakdowns could occur inside the plant. Tom said there were many potential difficulties. Leaks might develop in the cooling system which would lead to corrosion. The cadmium rods might wear out, or break, or even become jammed in their sleeves.

"Thermocouples-electric thermometers used to measure the temperature- may require replacement," Tom went on. "Then, as you know, any building is affected by weather and ground disturbances. The concrete in the inner plant may crack and have to be repaired with mortar. Certain iron parts will rust and these must be painted from time to time-two more very necessary jobs for the giant robot."

Bud remarked that there was one important use for the robot that Tom had not mentioned. "It has to do with sabotage," he said.

"How in the world could there be sabotage when the Citadel is so well protected?" Phyl asked.

"Easy," said Sandy. "Somebody could drop a bomb on the plant."

"That's why I'm going to set up a system of drone planes over Dad's plant,"

said Tom. "Then, too, anyone who got past our security officers might manufacture a bomb that looked like one of the ura- ARV UNDER SUSPICION 107.

nium slugs and send it in with the regular slugs."

Bud whistled. "When that exploded, good night! No more atomic energy plant."

"But that won't be the case at the Citadel," Tom said. "Even a bomb detonating inside it would not ruin the whole plant. But only the robot could restore the damaged pile to working order."

"Tell me more about Stan Lee's job," Phyl said.

"All he's going to do this trip," said Tom, "is walk around. First, I want to be sure that the control board is working properly. Second, that Stan Lee makes the turns at the right time, and responds inside the building when he gets the signal."

There was a knock at the rear of the lounge and the young people turned to see Chow standing there with a wide grin on his face. He was holding a large tray heaped with sandwiches, cookies, and milk.

"If you-all kin stop conferrin' long enough for a lil ole Texas snack, I'll be glad to bring this forward."

"Bring 'em along!" Bud cried. "What's in those sandwiches, though? Hope they're not cactus specials. I'm not that starved!"

Chow ignored Bud's remarks as he set the tray on a permanent wall table.

"I always said," he drawled, "if you use your haid too hard you forgit your stomach and then you gits into trouble. Yup-a lil ole snack now an' then keeps you agoin'."

Sandy laughed and said she could not think of any 108 TOM SWIFT AND MIS GIANT ROBOT.

nicer way to keep going. But Bud was not inclined to let the chef off so easily.

He bit into one of the sandwiches, choked, and cried: "Man! This is worse than cactus! Tastes like cement and red peppers!"

The former chuck-wagon cook looked hurt. "Bud Barclay, you-all don't know a good thing when you eat it. That's jest a plain old chicken sandwich- with some ground-up nuts and horseradish sauce. I learned about it from a Chinese cook."

"Well, you can give that recipe back to your Chinese friend," retorted Bud.

There actually were tears in his eyes and Chow finally admitted that perhaps he had put too much horseradish in the sandwich.

Suddenly Bud realized that he had not chosen the sandwich himself. Chow had handed it to him. He looked at the cook with suspicion in his eyes. But before he could say anything more, Chow fled.

Tom roared with laughter. "I guess after this, Bud, you'll think twice before you kid Chow about his cooking."

The rest of the food was delicious, and Sterling and Hanson declared that if it were a sample of the meals they were to have on the rest of the trip, they would vote Chow the best cook in the West.

Two hours later they were winging over eroded scrub country and Tom went back to the pilot's seat. Below the ship great black boulders, cracked by weathering, were strewn about like so many pebbles.

ARV UNDER SUSPICION 109.

Rusty valleys of clay, splotched with green rivulets and caked yellow terraces, broke the plains into forked patterns.

There was not a sign of civilization. Here and there yucca trees poked their spines into the arid air. A few minutes later they were flying over a vast level area, obviously smoothed by man's efforts.

"Here we are!" Tom announced.

On the flat surface stood a cl.u.s.ter of ultramodern structures. Standing apart at one edge were dormitories. Laboratory and office buildings were scattered in a loose pinwheel formation around the perimeter.

From its center rose a long, ma.s.sive boxlike rectangle. The concrete building was windowless, its thick walls broken only by ventilating shafts. This was the building to house the atomic pile. It would be encased in concrete, deep within the building's double walls.

As Tom circled once over the area, Bud asked where they would land.

"About ten miles from here," Tom replied, flying away from the plant, "halfway between the nearest town and the Citadel. More convenient for all of us that way."

Presently he cut the forward engines and set the jet lifters in motion. Then, gradually, he cut power and the ship touched ground. As the travelers got out, Phyl remarked: "Look at all this s.p.a.ce! Just rocks and desert as far as you can see!"