“And was there anything that tended to throw suspicion upon anyone?” asked Thorndyke.

“Why, yes,” said Mr. Lawley, with an uncomfortable glance at his client, “unfortunately there was.  It seemed that the person who abstracted the diamonds must have cut or scratched his thumb or finger in some way, for there were two drops of blood on the bottom of the safe and one or two bloody smears on a piece of paper, and, in addition, a remarkably clear imprint of a thumb.”  “Also in blood?” asked Thorndyke.

“Yes.  The thumb had apparently been put down on one of the drops and then, while still wet with blood, had been pressed on the paper in taking hold of it or otherwise.”

“Well, and what next?”

“Well,” said the lawyer, fidgeting in his chair, “to make a long story short, the thumb-print has been identified as that of Mr. Reuben Hornby.”

“Ha!” exclaimed Thorndyke.  “The plot thickens with a vengeance.  I had better jot down a few notes before you proceed any further.”

He took from a drawer a small paper-covered notebook, on the cover of which he wrote “Reuben Hornby,” and then, laying the book open on a blotting-pad, which he rested on his knee, he made a few brief notes.

“Now,” he said, when he had finished, “with reference to this thumb-print.  There is no doubt, I suppose, as to the identification?”

“None whatever,” replied Mr. Lawley.  “The Scotland Yard people, of course, took possession of the paper, which was handed to the director of the finger-print department for examination and comparison with those in their collection.  The report of the experts is that the thumb-print does not agree with any of the thumb-prints of criminals in their possession; that it is a very peculiar one, inasmuch as the ridge-pattern on the bulb of the thumb—­which is a remarkably distinct and characteristic one—­is crossed by the scar of a deep cut, rendering identification easy and infallible; that it agrees in every respect with the thumb-print of Mr. Reuben Hornby, and is, in fact, his thumb-print beyond any possible doubt.”

“Is there any possibility,” asked Thorndyke, “that the paper bearing the thumb-print could have been introduced by any person?”

“No,” answered the lawyer.  “It is quite impossible.  The paper on which the mark was found was a leaf from Mr. Hornby’s memorandum block.  He had pencilled on it some particulars relating to the diamonds, and laid it on the parcel before he closed up the safe.”

“Was anyone present when Mr. Hornby opened the safe in the morning?” asked Thorndyke.

“No, he was alone,” answered the lawyer.  “He saw at a glance that the diamonds were missing, and then he observed the paper with the thumb-mark on it, on which he closed and locked the safe and sent for the police.”

“Is it not rather odd that the thief did not notice the thumb-mark, since it was so distinct and conspicuous?”