"They're probably laying low getting ready to strike again," Tom thought but kept this worry to himself.

ROBOT TENNIS 153.

The following morning he moved into his private quarters which opened off the special testing laboratory at the Enterprises plant. For a week the youthful scientist buried himself in work, seeing no one but Chow. The cook hovered over Tom like a fretful hen, seeing to it that the absorbed young inventor had enough food and a proper amount of rest.

One afternoon Bud Barclay was startled to receive an intercom phone call from his friend. He was even more amazed when Tom asked: "How about a robot game of tennis with me?"

"Have you gone off your rocker?" Bud cried.

Tom laughed. "Don't worry. I'm okay. My two giants are ready for a co- ordination test. I need your help."

"A game of tennis between two headless giants! This I want to seel" Bud howled. "I'll be right over."

When Bud arrived he found the two giants had temporary heads with antenna "hair" but the camera "eyes" were missing. Chow had dug up two rackets and carried them as the boys marched the two giant robots out of the building to a court behind the main offices.

Tom had arranged for two portable relotrol outfits, tuned to different frequencies, to be set up at each side of the court.

"My controls are going to have some pretty fast compensating to do." Bud grinned. "Score will be fi-O in my robot's favor!"

154 .

"You're on!" Tom laughed as he placed his racket in the metal fingers of his robot. He eyed the windows behind them. "If my giant overcorrects," he warned, "we're in for some broken-window bills!"

"Toss you for first serve," Bud yelled, adjusting the magnitude-and-action blending controls. His robot took a vicious slash at the ball.

Tom laughed. "Net ball!"

ROBOT TENNIS 155.

His robot took a swing. The ball bounded back across the court. The game was on!

The extraordinary sight of two metal automatons, whacking a tennis ball, darting for rebounds, and charging the net, drew a large audience of plant workers. They cheered and whistled each time a ball was missed or a clever drive completed.

156 .

"Brand my sunfishin' horse!" cried Chow. "This sure is the confoundinest game I ever did see!"

Tom's robot had trouble gauging the service line, while Bud's kept slamming out of the court on overhand returns. The boys' hands flew from hand control to foot angle directors and the robots' motors were constantly reversing.

At first the giants tended to exaggerate their motions, with the result that the game was clumsy and far from professional. As the game progressed, however, the automatons grew more adept and play became subtle and fine.

Suddenly Bud yelled, "Tom, this is for the time you took over Herbert in the skit!"

His robot drove a slashing ball to the corner of the court. Tom was unable to direct his robot to return it.

In the end, Bud's robot won the game, which had gone to deuce five times.

Tom made his robot jump the net to congratulate the winning giant and the audience clapped in appreciation of the show.

Tom was pleased with the co-ordination of his metal men and told Bud only one thing remained to be done now before the giants would be ready for shipment to the Citadel.

"What's that?"

The inventor said that the television cameras, which would be the "eyes" of the robot to report what was happening inside the atomic energy plant, worked well enough under ordinary circ.u.mstances.

ROBOT TENNIS 157.

But the phosphors on the screens of the camera tubes were sensitive to the invisible but powerful radiation produced by the radioactive materials in the pile.

This intense radiation would fog the picture on the iconoscope face and literally blind the robot.

Throughout the late afternoon and early evening, Tom labored over the problem. The cameras themselves were protected by asbestalon. The problem was how to keep the radiation from entering through the lens. A few experiments with niters proved fruitless.

Finally, the young inventor set up a series of mirror light baffles. These caught the visible light and reflected it into the tube while absorbing and deflecting the harmful radiation. Thus the screen was protected. After several hours of adjustments, the reflection principle was fully perfected!

Tom was now satisfied with the "eyes" of his robot. Excitedly he closed the laboratory with the thought of going home and telling his mother. She must be the first to know of his success!

As he started down the corridor he heard his telephone ring. Unlocking the door, he picked up the receiver.

A strained, faraway voice said, "Tom Swift?"

"Yes."

"This is Marco. Please," the man said in a pleading tone, "if you'll promise not to punish me, I'll lead you to the person who is back of all your troubles-the man who's after your robot."

CHAPTER 19.

THE WATCHMAN'S CONFESSION.

THE UNEXPECTED WORDS of the night watchman startled Tom. Perhaps Marco was not a traitor after all!

"How soon can you be at my office?" Tom asked.

"I don't dare come to the plant, Tom," the trembling voice whispered in reply.

"I'm afraid that someone might see me."

"Why did you spy against us, Marco?" Tom asked, trying to draw the elderly man out while he was in contact with him.

"He-he hypnotized me. He put me under a-a spell, so I had to help him."

"Who put you under a spell, Marco?"

"Please, Tom," the man pleaded. "I don't want to say any more over the telephone. I'm terribly afraid. I'm sorry if I've done you or your father any harm. I'll do anything to make it up."

158.

THE WATCHMAN'S CONFESSION 159.

Tom checked his wrist watch. "Go to the York Hotel in downtown Shopton,"

he instructed. "Take a room there and wait for me. I'll be up at eleven o'clock."

"Right, Tom. I'll do just that," the man promised.

Tom broke the connection and signaled the operator. In rapid order he placed a double-circuit call to Radnor on one line and Bud on another.

"I'm not absolutely sure that Marco is on the level," he said, after reporting his conversation with the watchman. "For all we know, it could be another ambush."

"Do you think they'd risk an attack on a crowded street?" Bud asked.

"I told Marco to take a hotel room," Tom replied.

"Just the same," Radnor broke in, "I wouldn't put anything past those bank robbers."

Tom arranged to have both Bud and Radnor follow him to the hotel.

"We'll meet a block away and you two amble along behind me," he instructed. "In that way we'll be ready for any attack."

The arrival was timed accurately and Tom's every move was covered precisely according to plan. There were no attempts on Tom during the walk to the York Hotel. He entered the lobby through a revolving door and reached the room-clerk's desk without being stopped.

Bud and Radnor followed him up a stairway to Marco's room but remained in the corridor. The 160 .

security officer held the toe of one shoe against the door to keep it open a crack.

The guard was in tears and almost cringed as he began the tale of his misdeeds.

"He mesmerized me, that's what he did. Talked on and on in a low voice till he had me in a trance. I couldn't help carrying out his commands. When I started obeying him I couldn't stop. Till now, that is. I'm through with him."

"Who was this person?" Tom asked.

"Raymond Turnbull."

The escaped mental patient!

Marco continued, "He was waiting outside my house one night when I got home. I live alone, you know. He came every night after that and we talked. I'd get sleepier and sleepier.

"Somehow I fell under his power. Turnbull made me bring him the model of the Flying Lab, and he put the recording machine in it. Every night I'd change the tape. Sometimes I'd bring it to a board-inghouse. Other times I'd mail it to a box number. When Mr. Billing called you about locating the shack, I overheard him and phoned Raymond at the boardinghouse."

"What's the address of the house?" Tom asked.

The old watchman thought for a moment. "I can't remember-I think it's Bond Street. But I can take you there. It's on the outskirts of town to the south."

"We'll go there at once," Tom decided.

When the two came out of the room, Bud and THE WATCHMAN'S CONFESSION 161.

Radnor were hidden in an alcove, but the shadowing arrangement continued as soon as they all left the hotel.

The watchman and Tom went directly to the neighborhood where the boardinghouse was located. At Bond Street they turned onto the quiet residential street.

Behind, Bud and Radnor kept a sharp lookout for signs of a trap. Bud was trailing in the shadows of trees and houses, while Radnor came up the block on the other side.

It was exceptionally dark and they had to depend on a few street lights, s.p.a.ced at wide intervals, for illumination. Tom instinctively slowed down as he approached the house, which had a porch across the front. He listened carefully to judge when Bud and Rad would be in the best position to cover his entrance.

There was no sound except that of his friends' footsteps. Then the stillness was broken by a high-pitched scream. It seemed to have come from the boardinghouse toward which they were heading!

"It sounded like a woman 1" Tom cried, then called, "Bud, you and Rad stay under cover till I signal you."

Bud and Radnor darted for concealment into some bushes across the street.

They heard the front door of the boardinghouse slam shut and saw a porch light flash on.

A man began to pound on the door. His features 162 .

were clearly visible in the light. The next second Marco cried out: "I know that man! He's one of the doctors from Blackstone."

The man heard him and turned to look. As Marco and Tom ran up, the doctor exclaimed, "Marco! What are you doing here?"

Stammering in confusion, Marco introduced Tom and Dr. Morrow and said they were looking for Raymond Turnbull.

"So am I," said Dr. Morrow. "The hospital finally traced him to this address, but when I spoke to the landlady, she became hysterical and shut the door in my face. She claims Turnbull's gone and she wants nothing to do with any more gangsters."

"Maybe I can help," Tom said. He rapped on the door and called out: "It's all right to let us in. This is Tom Swift of Swift Enterprises."

The woman peered at him from behind a curtain in the hall window. Then, evidently recognizing the young inventor from newspaper pictures, she opened the door and invited the callers into her living room.

Dr. Morrow introduced himself again and told why he had come. "Raymond Turnbull escaped from our mental hospital about a month ago," he said. "Will you please tell us what you know about him and where I may find him."

"I can't tell you where he is," said the woman, adding that her name was Mrs.

Riley. She apologized for her hysteria and explained, "I've been THE WATCHMAN'S CONFESSION 163.

terribly upset by what's happened. When Mr. Turn-bull first took the room he told me he was a professor. I never paid much attention to him. He spent all his time with his papers and studies. I thought he was a fine gentleman.

"Then he began to have callers. One night a swarthy-looking man with a mustache came. I kept thinking he looked familiar. The next morning I remembered seeing his picture in a newspaper. He was a member of that Briggin gang. The one they call Slick."

Mrs. Riley held her handkerchief to her nose and began to sniffle. "Oh, I was so upset. I started to call the police. Just then, one of my other boarders told me he'd left in the middle of the night. Took all his things with him-even the funny tape machine he had. I was so relieved to have him gone that I didn't bother to notify the police."