Dr. O’Connor came into the lighted square of screen slowly, looking all around him. “This is very fascinating,” he said, blinking in the lamplight. “I hadn’t realized that you people took so many precautions—”

He was, Malone thought, somewhere between fifty and sixty, tall and thin with skin so transparent that he nearly looked like a living X-ray. He had pale blue eyes and pale white hair, and, Malone thought, if there ever were a contest for the best-looking ghost, Dr. Thomas O’Connor would win it hands (or phalanges) down.

“This is all necessary for the national security,” Burris said, a little sternly.

“Oh,” Dr. O’Connor said quickly. “I realize that, of course. Naturally. I can certainly see that.”

“Let’s go ahead, shall we?” Burris said.

O’Connor nodded. “Certainly. Certainly.”

Burris said: “Well, then,” and paused. After a second he started again: “Now, Dr. O’Connor, would you please give us a sort of verbal run-down on this for our records?”

“Of course,” Dr. O’Connor said. He smiled into the video cameras and cleared his throat. “I take it you don’t want an explanation of how this machine works. I mean: you don’t want a technical exposition, do you?”

“No,” Burris said, and added: “Not by any means. Just tell us what it does.”

Dr. O’Connor suddenly reminded Malone of a professor he’d had in college for one of the law courses. He had, Malone thought, the same smiling gravity of demeanor, the same condescending attitude of absolute authority. It was clear that Dr. O’Connor lived in a world of his own, a world that was not even touched by the common run of men.

“Well,” he began, “to put it very simply, the device indicates whether or not a man’s mental — ah — processes are being influenced by outside — by outside influences.” He gave the cameras another little smile. “If you will allow me, I will demonstrate on the machine itself.”

He took two steps that carried him out of camera range, and returned wheeling a large heavy-looking box. Dangling from the metal covering were a number of wires and attachments. A long cord led from the box to the floor, and snaked out of sight to the left.

“Now,” Dr. O’Connor said. He selected a single lead, apparently, Malone thought, at random. “This electrode—”

“Just a moment, Doctor,” Burris said. He was eyeing the machine with a combination of suspicion and awe. “A while back you mentioned something about ‘outside influences.’ Just what, specifically, does that mean?”

With some regret, Dr. O’Connor dropped the lead. “Telepathy,” he said. “By outside influences, I meant influences on the mind, such as telepathy or mind-reading of some nature.”

“I see,” Burris said. “You can detect a telepath with this machine.”

“I’m afraid—”

“Well, some kind of a mind-reader anyhow,” Burris said. “We won’t quarrel about terms.”

“Certainly not,” Dr. O’Connor said. The smile he turned on Burris was as cold and empty as the inside of Orbital Station One. “What I meant was — if you will permit me to continue — that we cannot detect any sort of telepathy or mind-reader with this device. To be frank, I very much wish that we could; it would make everything a great deal simpler. However, the laws of psionics don’t seem to operate that way.”

“Well, then,” Burris said, “what does the thing do?” His face wore a mask of confusion. Momentarily, Malone felt sorry for his chief. He could remember how he’d felt, himself, when that law professor had come up with a particularly baffling question in class.

“This machine,” Dr. O’Connor said with authority, “detects the slight variations in mental activity that occur when a person’s mind is being read.”

“You mean, if my mind were being read right now—”

“Not right now,” Dr. O’Connor said. “You see, the bulk of this machine is in Nevada; the structure is both too heavy and too delicate for transport. And there are other qualifications—”

“I meant theoretically,” Burris said.

“Theoretically—” Dr. O’Connor began, and smiled again — “Theoretically, if your mind were being read, this machine would detect it, supposing that the machine were in operating condition and all of the other qualifications had been met. You see, Mr. Burris, no matter how poor a telepath a man may be, he has some slight ability — even if only very slight — to detect the fact that his mind is being read.”

“You mean, if somebody was reading my mind, I’d know it?” Burris said. His face showed, Malone realized, that he plainly disbelieved this statement.

“You would know it,” Dr. O’Connor said, “but you would never know you knew it. To elucidate: in a normal person — like you, for instance, or even like myself — the state of having one’s mind read merely results in a vague, almost sub-conscious feeling of irritation, something that could easily be attributed to minor worries, or fluctuations in one’s hormonal balance. The hormonal balance, Mr. Burris, is—”

“Thank you,” Burris said with a trace of irritation. “I know what hormones are.”

“Ah. Good,” Dr. O’Connor said equably. “In any case, to continue: this machine interprets those specific feelings as indications that the mind is being — ah — ‘eavesdropped’ upon.”

You could almost see the quotation marks around what Dr. O’Connor considered slang dropping into place, Malone thought.

“I see,” Burris said with a disappointed air. “But what do you mean, it won’t detect a telepath? Have you ever actually worked with a telepath?”

“Certainly we have,” Dr. O’Connor said. “If we hadn’t, how would we be able to tell that the machine was, in fact, indicating the presence of telepathy? The theoretical state of the art is not, at present, sufficiently developed to enable us to—”

“I see,” Burris said hurriedly. “Only wait a minute.”

“Yes?”

“You mean you actually got a real mind-reader? You’ve found one? One that works?”

Dr. O’Connor shook his head sadly. “I’m afraid I should have said, Mr. Burris, that we did once have one,” he admitted. “He was, unfortunately, an imbecile, with a mental age between five and six, as nearly as we were ever able to judge.”

“An imbecile?” Burris said. “But how were you able to—”

“He could repeat a person’s thoughts word for word,” Dr. O’Connor said. “Of course, he was utterly incapable of understanding the meaning behind them. That didn’t matter; he simply repeated whatever you were thinking. Rather disconcerting.”

“I’m sure,” Burris said. “But he was really an imbecile? There wasn’t any chance of—”

“Of curing him?” Dr. O’Connor said. “None, I’m afraid. We did at one time feel that there had been a mental breakdown early in the boy’s life, and, indeed, it’s perfectly possible that he was normal for the first year or so. The records we did manage to get on that period, however, were very much confused, and there was never any way of telling anything at all, for certain. It’s easy to see what caused the confusion, of course: telepathy in an imbecile is rather an oddity — and any normal adult would probably be rather hesitant about admitting that he was capable of it. That’s why we have not found another subject; we must merely sit back and wait for lightning to strike.”

Burris sighed. “I see your problem,” he said. “But what happened to this imbecile boy of yours?”

“Very sad,” Dr. O’Connor said. “Six months ago, at the age of fifteen, the boy simply died. He simply — gave up, and died.”

“Gave up?”

“That was as good an explanation as our medical department was able to provide, Mr. Burris. There was some malfunction — but — we like to say that he simply gave up. Living became too difficult for him.”

“All right,” Burris said after a pause. “This telepath of yours is dead, and there aren’t any more where he came from. Or if there are, you don’t know how to look for them. All right. But to get back to this machine of yours: it couldn’t detect the boy’s ability?”