"That's right," Malone said. "Where'd an imbecile get words like 'psychocerebral?' I don't think I know what that means, myself." "Ah," Dr. O'Connor said. "But that's not _his_ vocabulary, you see. What Charlie is doing is simply repeating the thoughts of those around him. He jumps from mind to mind, simply repeating whatever he receives." His face assumed the expression of a man remembering a bad taste in his mouth. "That's how we found him out, Mr. Malone," he said. "It's rather startling to look at a blithering idiot and have him suddenly repeat the very thought that's in your mind." Malone nodded unhappily. It didn't seem as if O'Connor's information was going to be a lot of help as far as catching a telepath was concerned. An imbecile, apparently, would give himself away if he were a telepath. But nobody else seemed to be likely to do that. And imbeciles didn't look like very good material for catching spies with. Then he brightened. "Doctor, is it possible that the spy we're looking for really isn't a spy?" "Eh?" "I mean, suppose he's an imbecile, too? I doubt whether an imbecile would really be a spy, if you see what I mean." Dr. O'Connor appeared to consider the notion. After a little while he said: "It is, I suppose, possible. But the readings on the machine don't give us the same timing as they did in Charlie's case--or even the same sort of timing." "I don't quite follow you," Malone said. Truthfully, he felt about three miles behind. But perhaps everything would clear up soon. He hoped so. On top of everything else, his feet were now hurting a lot more. "Perhaps if I describe one of the tests we ran," Dr. O'Connor said, "things will be somewhat clearer." He leaned back in his chair. Malone shifted his feet again and transferred his hat from his right to his left hand. "We put one of our test subjects in the insulated room," Dr. O'Connor said, "and connected him to the detector. He was to read from a book-- a book that was not too common. This was, of course, to obviate the chance that some other person nearby might be reading it, or might have read it in the past. We picked _The Blood is the Death_ by Hieronymus Melanchthon, which, as you may know, is a very rare book indeed." "Sure," Malone said. He had never heard of the book, but he was, after all, willing to take Dr. O'Connor's word for it. The telepathy expert went on: "Our test subject read it carefully, scanning rather than skimming. Cameras recorded the movements of his eyes in order for us to tell just what he was reading at any given moment, in order to correlate what was going on in his mind with the reactions of the machine's indicators, if you follow me." Malone nodded helplessly.