"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?"
"No, I think not," answered Mr. Lawley. "The paper was lying face downwards on the bottom of the safe, and it was only when he picked it up and turned it over that Mr. Hornby discovered the thumb-print. Apparently the thief had taken hold of the parcel, with the paper on it, and the paper had afterwards dropped off and fallen with the marked surface downwards—probably when the parcel was transferred to the other hand."
"You mentioned," said Thorndyke, "that the experts at Scotland Yard have identified this thumb-mark as that of Mr. Reuben Hornby. May I ask how they came to have the opportunity of making the comparison?"
"Ah!" said Mr. Lawley. "Thereby hangs a very curious tale of coincidences. The police, of course, when they found that there was so simple a means of identification as a thumb-mark, wished to take thumb-prints of all the employees in the works; but this Mr. Hornby refused to sanction—rather quixotically, as it seems to me—saying that he would not allow his nephews to be subjected to such an indignity. Now it was, naturally, these nephews in whom the police were chiefly interested, seeing that they alone had had the handling of the keys, and considerable pressure was brought to bear upon Mr. Hornby to have the thumb-prints taken.
"However, he was obdurate, scouting the idea of any suspicion attaching to either of the gentlemen in whom he had reposed such complete confidence and whom he had known all their lives, and so the matter would probably have remained a mystery but for a very odd circumstance.
"You may have seen on the bookstalls and in shop windows an appliance called a 'Thumbograph,' or some such name, consisting of a small book of blank paper for collecting the thumb-prints of one's friends, together with an inking pad."
"I have seen those devices of the Evil One," said Thorndyke, "in fact, I have one, which I bought at Charing Cross Station."
"Well, it seems that some months ago Mrs. Hornby, the wife of John Hornby, purchased one of these toys—"
"As a matter of fact," interrupted Reuben, "it was my cousin Walter who bought the thing and gave it to her."