Marco had begun to shake. It was evident that he had had no idea Raymond Turnbull was mixed up with bank robbers!

"Oh," the watchman wailed, "I never thought-"

He was interrupted by Tom, whose eyes were riveted on a metal picture frame that hung opposite one of the opened living-room windows. As he stared, the frame began to glow dimly with an orange light.

"Quick!" he cried, as the picture gla.s.s suddenly shattered with a loud crack.

"Hit the floor, everybody I"

CHAPTER 20.

THE MASKED INTRUDER.

AS TOM SHOUTED the warning, he ducked below the window sash. Dr.

Morrow followed suit. Marco and Mrs. Riley seemed fl.u.s.tered by Tom's sudden orders. The watchman lost his balance and sprawled aimlessly beneath a large oak table, while the woman froze, her eyes bulging at the sight of the orange light still playing on the picture frame.

"I think someone in the yard is trying to knock us out with a heat ray," Tom whispered. "Get down! Play dead!" He crumpled into an inert heap near the door, setting an example for the others.

The announcement was too much for the frightened landlady who immediately fainted, making the situation even more realistic. Marco and the doctor lay motionless.

Out of the corner of one eye, Tom watched the 164.

THE MASKED INTRUDER 165.

front door. In a moment he heard a click and the door opened.

A masked man stood there. He was of medium height with dark hair. In one hand he carried what Tom a.s.sumed to be the knockout weapon-a monochromatic infrared beamer.

Stepping into the living room, he paused and surveyed the limp bodies.

Apparently satisfied, he started for the stairway.

As soon as the masked intruder had vanished up the steps, Tom crawled along the floor to the front door. Cautiously he opened it. Luck was with him. The hinges did not squeak.

Tom reached for the flashlight in his pocket and held it at arm's length out the door. He blinked the beam three times in rapid succession. Then he sent three longer flashes, following these with three more short ones-the international signal of distress. He hoped Bud and Radnor were watching carefully and that they realized from the silence of his plea the need for extreme caution.

Tom left the door ajar, removed his shoes, and tiptoed to the stairway. He took each step with extreme care, knowing that one chance creak of a board and the intruder would come running and use the ray at close range.

"Who can he be?" Tom wondered. "Raymond Turnbull?"

Reaching the head of the stairs, he looked down 166 .

a narrow hallway. A few feet ahead of him the masked stranger was kneeling before a vent in the building's air-heating system. He had lifted the vent grill and was reaching inside, apparently groping for something.

The man withdrew his hand, obviously satisfied. By the hall light Tom could see that he was holding a small metal panel with a red b.u.t.ton on it. Several wires dangled free at one end.

With the man intensely absorbed in the device and the beamer lying on the floor beside him, Tom knew this was the moment for action.

He leaped, caught the man off balance, and knocked him to the floor, rolling him away from the beamer. A scuffle followed, but finally both got to their feet.

The masked man swung furiously at Tom and kicked him viciously.

Tom retaliated with three quick uppercuts that staggered his opponent. In desperation the man dived at Tom, slammed him against the banister, and lunged for the beamer.

Tom grabbed his ankles with a flying tackle that sent the masked man sprawling. Bud, with Radnor at his heels, charged up the stairs and grabbed the beamer while Radnor unmasked the man.

"Slick Steck!" Radnor cried.

While the prisoner glared in hatred at his captors, Steck was marched downstairs, where Mrs. Riley was being revived by Dr. Morrow. She opened her eyes and gazed in terror.

THE MASKED INTRUDER 167.

"Oh!" she screamed. "That's the man! It's that Slick fellow!"

"Start talking, Slick!" Radnor barked at the bank robber.

"I'm not saying a word," replied the man. "You've got nothing on me."

"Okay. We'll let the police do it." Tom turned away.

A cunning light came into the prisoner's eyes. "I might trade a little information for my freedom," he said. "Just what is it you're interested in finding out, Swift?"

"We're interested in all your dealings with Raymond Turnbull."

He expected the mention of the name to surprise the bank robber. Instead, Tom was the surprised one.

"Are you crazy?" Slick Steck snarled. "I haven't been working with Raymond Turnbull. You've got your names mixed. I've been-er-conducting business arrangements with the professor himself, Robert Turnbull."

The disclosure electrified his listeners. Before they recovered their composure, Steck continued.

"Sure I worked with the prof. It was a two-way venture. He was going to make bank robbing a safe and easy proposition for us-a sure thing. In return, the gang would take care of a few little matters for him, here in Shopton, while he was out of town on some other business."

168 .

"At the atom plant, no doubt," thought Tom.

Radnor prodded Steck with another question. "Just how would these holdups be accomplished?"

"With a robot," he replied. "It was going to be great. He promised to get us one of Tom Swift's robots. It would have a machine gun mounted on the end of one arm." Steck laughed hollowly. "The thing would have been rigged up like a walking tank. No bank-guard's bullets or tear-gas bombs could have stopped it.

The robot would just walk right out with the money."

Tom, although enraged at this scheme, was intrigued by its ingenious idea.

"Where was the robot going to be controlled from?"

Steck replied, "The whole operation would have been worked from an innocent-looking car."

"What about after the robbery?" said Bud. "Wouldn't the robot be followed?"

"Turnbull thought of everything," their prisoner explained. "The banks chosen to be robbed would always be near a river and the robot would disappear into the water and walk under the surface to a secret meeting place miles away. You know how fast those things can go if you want them to. Then he'd come up and we'd get the money."

Astounded at the disclosure, Tom felt that he should get in touch with his father at once. But first he must learn all he could from the prisoner.

"The prof was teaching my friends and me a lot of scientific stuff," said the ex-convict, smirking. "He THE MASKED INTRUDER 169.

showed us how to use all sorts of small machines like the monochromatic infrared beamer you took away from me. That gimmick I took out of the vent upstairs is a new type of electrical control b.u.t.ton. A swivel switch, he calls it."

Tom examined the gadget. Its sliding segment enabled the single b.u.t.ton to do the work normally accomplished by an entire bank of toggle switches.

"I was supposed to hold on to it until Turnbull came to my house," Steck explained.

"And just where is that?" asked Radnor.

The gangster grew sullen. "I've told you all I'm going to tell you."

"Why did you tell us this much?" Bud asked, puzzled.

Steck was silent for a few seconds. Then he took a deep breath. "The reason I told you all this," he said, "is because you got nothing to hold me on. And furthermore, I'm through with Robert Turnbull. I think the guy's nuts. He's got a twin who's crazy, but I think Robert's worse."

CHAPTER 21.

TWIN TROUBLE.

THE POLICE were summoned by Radnor. Manacled and snarling, Slick Steck was taken by them to the Shopton jail. After they had gone, Bud turned to Tom.

"I don't get this about Robert Turnbull," he said. "You and your father thought he was perfectly sane, didn't you?"

"Yes, Bud, and that gives me an idea," said Tom. He turned to Marco. "Did you ever see Mr. Raymond Turnbull's twin brother?"

"Yes. Once about eight months ago when I was working at Blackstone. He came to visit Raymond. He's an identical twin."

"Then the man you thought was Raymond could have been Robert?" Tom asked.

"Oh, no. I couldn't be fooled. Anyway, Raymond talked about things that happened at Blackstone that his brother wouldn't know."

170.

TWIN TROUBLE 171.

"Then there's only one answer," Tom said. "Raymond must be impersonating his brother to avoid detection. The Briggin gang doesn't know that Robert is engaged in secret work at our atomic plant, so they wouldn't suspect Raymond's impersonation."

Dr. Morrow nodded. "And Raymond, as Robert, would not be in danger of being sent back to Black-stone."

"He even fooled the Briggin gang," Radnor added.

"It's tragic the way a fine mind will snap under the pressure of overwork,"

Tom remarked.

The doctor placed a hand on Tom's shoulder and said in a serious voice, "Raymond Turnbull's confinement at Blackstone was not due to overwork."

"What do you mean?"

"Well, his condition is one we run into quite often at the hospital. It developed like this. Raymond once made some incorrect calculations in a nuclear experiment, an understandable mistake in research of such a crucial nature.

"On the basis of that error a fellow physicist brought together a near-critical ma.s.s of plutonium, and, as a result, was subjected to radiation. Fortunately he recovered. However, Raymond, an extremely sensitive person, felt totally responsible and brooded over it so much that his mind snapped."

"Why didn't we hear any news of his escape?" Radnor asked.

"Because of the top-secret work he was doing prior 172 .

to his misfortune, our search for Raymond has been carried on without any publicity," the doctor replied.

"And would this condition explain his recent criminal a.s.sociations?" Tom queried.

"It's very likely," Dr. Morrow answered. "Physicians can never predict to what lengths such an obsession will drive a person. Almost any action is possible."

After a pause the doctor added, "I hope that you people will help the hospital authorities find this patient before he carries out the dire schemes we overheard him planning while he was at Blackstone. Oh, one thing I didn't make clear. His case isn't hopeless, but he needs further care and treatment."

"We'll sure do our best to find him," declared Bud, memories of his experience on the mesa still fresh in his mind.

Wishing to communicate with his father at once and give him the complete story, Tom said good-by to the others and went to his office. There he called the Citadel and gave Mr. Swift the full details.

The elder scientist was grave, remarking that the situation called for extreme care. Raymond Turn-bull's actions would doubtless be cunning and unpredictable.

"I'll have another talk with Robert Turnbull," he told his son. "It's possible that Raymond may communicate with him. I must admit, Tom, I won't feel comfortable until he's back at Blackstone."

TWIN TROUBLE 173.

"Do you think we should delay putting the pile into operation until we do know where he is, Dad?"

"I can't do that, Tom. It may be months or years before Raymond is located, and we can't postpone the official opening." Then he changed the subject, asking, "In the morning, will you find out about the two cybernetic arms and hands that are scheduled for shipment out here tomorrow?"

Mr. Swift was referring to the large mechanical sets which he had designed himself for use at the Citadel. Compared to similar ones on the market, however, these were smaller and lighter, yet equally dexterous. They would be suspended from an overhead rail at the point where radioactive slugs came from the oven.