"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.
