The sleek robot craft was rolled off an incline and along the ground. The three of them pushed it to a wide expanse of clearing.

122 .

A curious crowd of atomic scientists and workmen gathered around to observe as Tom rigged up a portable patrolscope and beeper box for the drone.

The plant's electricians helped him run a Citadel power line to the controls. First came a ground test with Tom working the controls. The ailerons flapped, the rudder turned, and the elevators moved and pivoted, all in response to his directions.

"Now for the test flight," Tom said, after exhaustive checks had been completed. "Conditions here are a lot different from those at Fearing Island. A low-flying drone might not respond fast enough to avoid hitting a sharp rock formation or a mesa."

"We'll have to test it for any possible static interference that it might encounter from the operation of the plant," his father commented.

Now the grueling air tests began. While Tom manipulated the beeper controls, the drone swept across the blue expanse of western sky. A silver streak, it darted in and out of jagged rock formations, and sliced through deep creva.s.ses. Suddenly the robot plane heeled over, out of control.

"What is it, Tom?" asked Hank.

"These rock mesas-they reflect signals as in a television 'ghost' picture."

Tom knew the drone must climb fast, as if on an interception mission.

Reaching the pinnacle of the climb, the drone regained its equilibrium.

"Whew!" Arv exclaimed in relief.

A few moments later Tom landed the ship.

STRANGE INDIAN STORY 123.

"I'll have to arrange a series of compensating directional towers for the signal," said Tom. "We can probably have the drone in the air by tomorrow. It will be set in a pattern to fly continuously over the plant."

Tom decided to wire the Enterprises plant for additional drones to be ferried to the Citadel.

"We'll need five more drones and a permanent control board," he said, "before I'll be satisfied that the protection here is adequate."

By the time Tom had worked out the specifications for the drone-control towers and turned them over to the engineers, it was dinnertime. He told his father that he planned to spend the night at the Flying Lab. He drove over in a jeep and was amazed to see a horse tethered near the Sky Queen. He parked and hurried up the ladder to the giant plant.

Reaching the doorway he stared in astonishment. Standing before him, arms folded, stood a tall, well-built Indian wearing buckskins and a denim shirt.

"Tom," called Sandy over the man's shoulder, "we were just going to drive over to the plant to find you. This is Chief Rob Featherlight of the local Zuiii tribe.

We visited his reservation today."

Tom relaxed and smiled. His sister had wasted no time in becoming acquainted with her neighbors. And apparently this neighbor was just as curious about their activities.

"This is a very fine plane," the young Indian re- 124 .

marked, as the group seated themselves in the lounge.

"The chief told us something this afternoon which I think you should hear from him at once, Tom," Sandy said.

The chief began his story. "There is trouble on my reservation. It has been caused by a large black crow. The bird has been flying overhead every day, just before sunset."

Tom exchanged glances with the others.

"But this crow," Featherlight went on, "does not fly like a crow. It banks like a plane does, not like a bird. Sometimes it flies at a speed so great as to bring fear to the hearts of my people. The older members of the council believe the bird to be an evil spirit that has returned to earth in this unnatural form." The chief paused a moment, then added, "I have been educated at public schools and know better."

"This crow," Tom asked excitedly, "did it ever come near the ground?"

"Only once. A young brave, our finest bow-and-arrow champion, tried to shoot it down. But the arrows just bounced off."

Tom's brow creased with worry. There was no doubt in his mind that the bird was one of the sinister mechanical crows that had tried to kill him!

Sandy looked at her brother with eyes filled with fear. "Oh, Tom, I'm scared.

You're not safe anywhere!"

CHAPTER 15.

A CRUCIAL TEST.

CHIEF FEATHERLIGHT stared perplexed at the Swifts and their friends.

Tom told him that the bird was mechanical and remote controlled, probably from a plane. Leaving all the gruesome details out of the story, he concluded by saying: "The crow is the work of a scientist who is trying to get his hands on some of our secret inventions. I'm sure that he intends no harm to the Zunis. Tell your people not to worry. The crow was only on a test flight."

The Indian seemed satisfied and arose, saying he would follow Tom's advice. The young inventor asked the chief to keep him informed of any further appearances of the crow. The man nodded, then descended the ladder and rode off on his horse.

Chow relaxed the tension somewhat by ringing a big dinner bell he had brought along on the trip. It never failed to get a smile.

125.

126 .

The cook announced that a barbecue would be served under the stars.

Everyone scrambled for the door.

Chow had arranged dinner chuck-wagon style. The girls perched on rocks and the boys sat cross-legged, Indian-fashion, around a crackling fire of charcoal.

As Chow broiled huge slabs of meat, Mr. Swift came to join them and spend the night.

"Yes, sir," said the talented chef, winking slyly at Tom, "there's nothin' like an open fire for steak. That's the way lizard meat was meant to be enjoyed."

Sandy refused to smile. She could not forget the danger that hung over her brother's every move.

"You've got to do something, Tom," she said finally.

"I'm taking reasonable precautions," her brother replied lightly. Then, as a joke, he added, "Do you want me to walk around with a distorter in my hat?"

"Yes," said Sandy. "That would be a very good idea."

"I agree," Phyl added. "That's just what you need. We'd worry a lot less."

Bud remarked that the girls were right. "Practically speaking," he said, "it would just be a matter of making a distorter small enough to fit into a hat." He envisioned a miniature apparatus resting on the inner crown frame of a ten-gallon hat.

Tom had already pulled a pencil from his pocket A CRUCIAL TEST 127.

and was drawing a diagram on the ground. "It could be done," he said. "The antenna would still work on a scale of, say-" He paused. "But I don't have a hat big enough."

The tension had been broken and the evening was spent pleasantly with Chow spinning yarns of the old West for Bud and the girls while Tom worked late in the plane's laboratory, redesigning the distorter to small scale.

The next morning a stack of flapjacks was waiting on the lounge table when the four young people and Mr. Swift appeared. Beside them lay three ten-gallon hats.

"Where did these come from?" Tom asked, puzzled.

Chow grinned. "I picked 'em up from the general store in town."

"Charles Winkler!" Tom exclaimed. "You old rascal! Why, you didn't know until last night that I wanted one."

Tom knew that Chow, a loyal horseman, never drove a jeep. And pintos were not part of the Sky Queen's equipment.

"How'd you get to town?" Tom asked.

"Why, brand the sunrise," said the cook, "an early-morning walk does wonders for the appet.i.te!"

"I know how you cowboys love to hike!" scoffed Tom, remembering it was a ten-mile walk to town. "Come on, Chow, give. Where did you get them?"

Chow said, with a twinkle in his eyes, that the ten- 128 .

gallon hats were for Tom, Mr. Swift, and Bud. "You kin put them there dees- torters in as many as you like." But he steadfastly refused to divulge his secret.

They all thanked him and Tom added, "I built two midget distorters during the night. Dad, I'll install one in your hat and the other in mine. I guess Bud won't need one to hunt for Indian treasure."

Bud had promised the girls that he would help them explore Purple Mesa.

After breakfast the boys rolled the Skeeter out of the hangar. Tom helped his sister and Phyl aboard while Bud checked the fuel supply of the squat helicopter.

Through the Skeeter's wide windows, Tom could see Sandy loading her camera.

Phyl, her sketching pad under her arm, waved happily in antic.i.p.ation of the day's fun.

Bud climbed into the pilot's seat. Four jet-tipped rotor blades began to rotate slowly at first, then whirled at tremendous speed. The ship rose slowly through the cloud of sand it had stirred up on the desert floor.

The bright-red helicopter made a gay picture as it sailed off with the sightseers. Tom watched until the craft was out of sight. Then he turned to the more serious matter of robot testing at the plant.

A crew had been at work since sunup with cranes and power shovels, clearing out the debris in the tunnel. When Tom and his father arrived they were able to put Stan Lee into action immediately. The flat-faced, man-sized robot created even more of a stir among the scientists than the drone plane had.

A CRUCIAL TEST 129.

Tom instructed the guards to keep everyone well back from the tunnel, however, in case of more trouble. He hoped that the circling drone plane would keep any unfriendly craft from the area.

Tom planned to walk the test robot through the tunnel and into the plant where it would simulate the route to be taken by the giant robot. He would use only the portable control board he had brought along.

The robot was lowered to the floor of the tunnel. For the complex journey, Tom had inserted three simultaneous action tapes in the control panel. As Mr.

Swift beamed a powerful torch into the gaping hole, Tom closed the switch that started the tapes. There was a faint whir as metal p.r.o.ngs scanned the tapes for instruction holes.

In a moment Stan Lee began to advance stiffly into the tunnel. Then he was out of sight. His movements now would be known only by the blinker lights on the control board.

"He'll make several turns following the tunnel," Tom remarked. "When he reaches the pile room, he should do a complete about-face and be back here in twenty minutes."

But five minutes later the lights for the first turn blinked a steady danger sign.

Stan Lee was in trouble!

Tom shut off the power. "He may have fallen, Dad!"

Quickly descending the ladder, Tom ran through 130 .

the tunnel. The robot had lost his balance on what should have been a relatively easy turn. He had landed face down and dented his chest.

Tom was shaking his head in puzzlement when his father joined him at the end of the tunnel. "This turn should have been almost automatic. Stan Lee performed it flawlessly many times in Shopton."

"It's very strange," Mr. Swift agreed.

The two studied the situation, rechecking the relays. Tom proposed that the answer might be right above their heads in the distorter hats.

"I hardly think so," Mr. Swift answered. "Those distorters are so small, their field is probably much too weak to interfere. There may be some factor in the plant that we've overlooked."

The Swifts returned to the Citadel's office to check blueprints and electrical- installation maps. The plant engineers delved deep into their files and unrolled large sheets of building plans showing where power-cable ducts lay. None of these, however, were near enough to the tunnel to interfere with the operation of the robot.

"I'm convinced that it's something more deep-seated than this," said Tom, after the scientists had left the room. "Stan Lee went out of control in the same way our jet plane did when it was captured by the crow, Dad."

"But our radarmen haven't reported anything flying near the Citadel," Mr.

Swift said.

Tom nodded, frowning. "There's no getting A CRUCIAL TEST 131.

around it, Dad. Someone took over the robot controls from inside the plant.

But how?"

Suddenly the young inventor cried, "Dad, the missing relotrol! Maybe it's been brought here."