the building periodically through the night.
"Now a very strange thing has occurred with regard to this safe. It happens that one of Mr. Hornby's customers in South Africa is interested in a diamond mine, and, although transactions in precious stones form no part of the business of the house, he has, from time to time, sent parcels of rough diamonds addressed to Mr. Hornby, to be either deposited in the bank or handed on to the diamond brokers.
"A fortnight ago Mr. Hornby was advised that a parcel of stones had been despatched by the Elmina Castle, and it appeared that the parcel was an unusually large one and contained stones of exceptional size and value. Under these circumstances Mr. Reuben was sent down to the docks at an early hour in the hope the ship might arrive in time for the stones to be lodged in the bank at once. Unfortunately, however, this was not the case, and the diamonds had to be taken to the works and locked up in the safe."
"Who placed them in the safe?" asked Thorndyke.
"Mr. Hornby himself, to whom Mr. Reuben delivered up the package on his return from the docks."
"Yes," said Thorndyke, "and what happened next?"
"Well, on the following morning, when the safe was opened, the diamonds had disappeared."
"Had the place been broken into?" asked Thorndyke.
"No. The place was all locked up as usual, and the caretaker, who had made his accustomed rounds, had heard nothing, and the safe was, outwardly, quite undisturbed. It had evidently been opened with keys and locked again after the stones were removed."
"And in whose custody were the keys of the safe?" inquired Thorndyke.
"Mr. Hornby usually kept the keys himself, but, on occasions, when he was absent from the office, he handed them over to one of his nephews—whichever happened to be in charge at the time. But on this occasion the keys did not go out of his custody from the time when he locked up the safe, after depositing the diamonds in it, to the time when it was opened by him on the following morning."
"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?"
"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."
"Well, that is not material," said Mr. Lawley (though I observed that Thorndyke made a note of the fact in his book); "at any rate, Mrs. Hornby became possessed of one of these appliances and proceeded to fill it with the thumb-prints of her friends, including her two nephews. Now it happened that the detective in charge of this case called yesterday at Mr. Hornby's house when the latter was absent from home, and took the opportunity of urging her to induce her husband to consent to have the thumb-prints of her nephews taken
