“Supposing,” said Thorndyke, “I make it clear to you that those prints on the window-pane were not made by Belfield. Would you still execute the warrant?”
“What do you think?” exclaimed Miller. “Do you suppose we should go into court to have you come and knock the bottom out of our case, like you did in that Hornby affair—by the way, that was a finger-print case too, now I come to think of it,” and the superintendent suddenly became thoughtful.
“You have often complained,” pursued Thorndyke, “that I have withheld information from you and sprung unexpected evidence on you at the trial. Now I am going to take you into my confidence, and when I have proved to you that this clue of yours is a false one, I shall expect you to let this poor devil Belfield go his way in peace.”
The superintendent grunted—a form of utterance that committed him to nothing.
“These prints,” continued Thorndyke, taking up the frame once more, “present several features of interest, one of which, at least, ought not to have escaped you and Mr. Singleton, as it seems to have done. Just look at that thumb.”
The superintendent did so, and then pored over the official paper.
“Well,” he said, “I don’t see anything the matter with it. It’s exactly like the print on the paper.”
“Of course it is,” rejoined Thorndyke, “and that is just the point. It ought not to be. The print of the thumb on the paper was taken separately from the fingers. And why? Because it was impossible to take it at the same time. The thumb is in a different plane from the fingers; when the hand is laid flat on any surface—as this window-pane, for instance—the palmar surfaces of the fingers touch it, whereas it is the side of the thumb which comes in contact and not the palmar surface. But in this”—he tapped the framed glass with his finger—“the prints show the palmar surfaces of all the five digits in contact at once, which is an impossibility. Just try to put your own thumb in that position and you will see that it is so.”
The detective spread out his hand on the table and immediately perceived the truth of my colleague’s statement.
“And what does that prove?” he asked.