“I had better,” said he, “give you a general outline of the case as it presents itself to the legal mind, and then my client, Mr. Reuben Hornby, can fill in the details if necessary, and answer any questions that you may wish to put to him.

“Mr. Reuben occupies a position of trust in the business of his uncle, John Hornby, who is a gold and silver refiner and dealer in precious metals generally.  There is a certain amount of outside assay work carried on in the establishment, but the main business consists in the testing and refining of samples of gold sent from certain mines in South Africa.

“About five years ago Mr. Reuben and his cousin Walter ­another nephew of John Hornby ­left school, and both were articled to their uncle, with the view to their ultimately becoming partners in the house; and they have remained with him ever since, occupying, as I have said, positions of considerable responsibility.

“And now for a few words as to how business is conducted in Mr. Hornby’s establishment.  The samples of gold are handed over at the docks to some accredited representative of the firm ­generally either Mr. Reuben or Mr. Walter ­who has been despatched to meet the ship, and conveyed either to the bank or to the works according to circumstances.  Of course every effort is made to have as little gold as possible on the premises, and the bars are always removed to the bank at the earliest opportunity; but it happens unavoidably that samples of considerable value have often to remain on the premises all night, and so the works are furnished with a large and powerful safe or strong room for their reception.  This safe is situated in the private office under the eye of the principal, and, as an additional precaution, the caretaker, who acts as night-watchman, occupies a room directly over the office, and patrols 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 for the inspection of the experts at Scotland Yard.  He pointed out that the procedure was really necessary, not only in the interests of justice but in the interests of the young men themselves, who were regarded with considerable suspicion by the police, which suspicion would be completely removed if it could be shown by actual comparison that the thumb-print could not have been made by either of them.  Moreover, it seemed that both the young men had expressed their willingness to have the test applied, but had been forbidden by their uncle.  Then Mrs. Hornby had a brilliant idea.  She suddenly remembered the ‘Thumbograph,’ and thinking to set the question at rest once for all, fetched the little book and showed it to the detective.  It contained the prints of both thumbs of Mr. Reuben (among others), and, as the detective had with him a photograph of the incriminating mark, the comparison was made then and there; and you may imagine Mrs. Hornby’s horror and amazement when it was made clear that the print of her nephew Reuben’s left thumb corresponded in every particular with the thumb-print that was found in the safe.

“At this juncture Mr. Hornby arrived on the scene and was, of course, overwhelmed with consternation at the turn events had taken.  He would have liked to let the matter drop and make good the loss of the diamonds out of his own funds, but, as that would have amounted practically to compounding a felony, he had no choice but to prosecute.  As a result, a warrant was issued for the arrest of Mr. Reuben, and was executed this morning, and my client was taken forthwith to Bow Street and charged with the robbery.”

“Was any evidence taken?” asked Thorndyke.

“No.  Only evidence of arrest.  The prisoner is remanded for a week, bail having been accepted in two sureties of five hundred pounds each.”

Thorndyke was silent for a space after the conclusion of the narrative.  Like me, he was evidently not agreeably impressed by the lawyer’s manner, which seemed to take his client’s guilt for granted, a position indeed not entirely without excuse having regard to the circumstances of the case.

“What have you advised your client to do?” Thorndyke asked presently.

“I have recommended him to plead guilty and throw himself on the clemency of the court as a first offender.  You must see for yourself that there is no defence possible.”

The young man flushed crimson, but made no remark.

“But let us be clear how we stand,” said Thorndyke.  “Are we defending an innocent man or are we endeavouring to obtain a light sentence for a man who admits that he is guilty?”

Mr. Lawley shrugged his shoulders.

“That question can be best answered by our client himself,” said he.

Thorndyke directed an inquiring glance at Reuben Hornby, remarking ­

“You are not called upon to incriminate yourself in any way, Mr. Hornby, but I must know what position you intend to adopt.”  Here I again proposed to withdraw, but Reuben interrupted me.

“There is no need for you to go away, Dr. Jervis,” he said.  “My position is that I did not commit this robbery and that I know nothing whatever about it or about the thumb-print that was found in the safe.  I do not, of course, expect you to believe me in the face of the overwhelming evidence against me, but I do, nevertheless, declare in the most solemn manner before God, that I am absolutely innocent of this crime and have no knowledge of it whatever.”

“Then I take it that you did not plead ’guilty’?” said Thorndyke.

“Certainly not; and I never will,” replied Reuben hotly.

“You would not be the first innocent man, by very many, who has entered that plea,” remarked Mr. Lawley.  “It is often the best policy, when the defence is hopelessly weak.”

“It is a policy that will not be adopted by me,” rejoined Reuben.  “I may be, and probably shall be, convicted and sentenced, but I shall continue to maintain my innocence, whatever happens.  Do you think,” he added, turning to Thorndyke, “that you can undertake my defence on that assumption?”

“It is the only assumption on which I should agree to undertake the case,” replied Thorndyke.

“And ­if I may ask the question ­” pursued Reuben anxiously, “do you find it possible to conceive that I may really be innocent?”

“Certainly I do,” Thorndyke replied, on which I observed Mr. Lawley’s eyebrows rise perceptibly.  “I am a man of facts, not an advocate, and if I found it impossible to entertain the hypothesis of your innocence, I should not be willing to expend time and energy in searching for evidence to prove it.  Nevertheless,” he continued, seeing the light of hope break out on the face of the unfortunate young man, “I must impress upon you that the case presents enormous difficulties and that we must be prepared to find them insuperable in spite of all our efforts.”

“I expect nothing but a conviction,” replied Reuben in a calm and resolute voice, “and can face it like a man if only you do not take my guilt for granted, but give me a chance, no matter how small, of making a defence.”

“Everything shall be done that I am capable of doing,” said Thorndyke; “that I can promise you.  The long odds against us are themselves a spur to endeavour, as far as I am concerned.  And now, let me ask you, have you any cuts or scratches on your fingers?”

Reuben Hornby held out both his hands for my colleague’s inspection, and I noticed that they were powerful and shapely, like the hands of a skilled craftsman, though faultlessly kept.  Thorndyke set on the table a large condenser such as is used for microscopic work, and taking his client’s hand, brought the bright spot of light to bear on each finger in succession, examining their tips and the parts around the nails with the aid of a pocket lens.

“A fine, capable hand, this,” said he, regarding the member approvingly, as he finished his examination, “but I don’t perceive any trace of a scar on either the right or left.  Will you go over them, Jervis?  The robbery took place a fortnight ago, so there has been time for a small cut or scratch to heal and disappear entirely.  Still, the matter is worth noting.”

He handed me the lens and I scrutinised every part of each hand without being able to detect the faintest trace of any recent wound.

“There is one other matter that must be attended to before you go,” said Thorndyke, pressing the electric bell-push by his chair.  “I will take one or two prints of the left thumb for my own information.”

In response to the summons, Polton made his appearance from some lair unknown to me, but presumably the laboratory, and, having received his instructions, retired, and presently returned carrying a box, which he laid on the table.  From this receptacle Thorndyke drew forth a bright copper plate mounted on a slab of hard wood, a small printer’s roller, a tube of finger-print ink, and a number of cards with very white and rather glazed surfaces.

“Now, Mr. Hornby,” said he, “your hands, I see, are beyond criticism as to cleanliness, but we will, nevertheless, give the thumb a final polish.”

Accordingly he proceeded to brush the bulb of the thumb with a well-soaked badger-hair nail-brush, and, having rinsed it in water, dried it with a silk handkerchief, and gave it a final rub on a piece of chamois leather.  The thumb having been thus prepared, he squeezed out a drop of the thick ink on to the copper plate and spread it out with the roller, testing the condition of the film from time to time by touching the plate with the tip of his finger and taking an impression on one of the cards.

When the ink had been rolled out to the requisite thinness, he took Reuben’s hand and pressed the thumb lightly but firmly on to the inked plate; then, transferring the thumb to one of the cards, which he directed me to hold steady on the table, he repeated the pressure, when there was left on the card a beautifully sharp and clear impression of the bulb of the thumb, the tiny papillary ridges being shown with microscopic distinctness, and even the mouths of the sweat glands, which appeared as rows of little white dots on the black lines of the ridges.  This manoeuvre was repeated a dozen times on two of the cards, each of which thus received six impressions.  Thorndyke then took one or two rolled prints, i.e. prints produced by rolling the thumb first on the inked slab and then on the card, by which means a much larger portion of the surface of the thumb was displayed in a single print.

“And now,” said Thorndyke, “that we may be furnished with all the necessary means of comparison, we will take an impression in blood.”

The thumb was accordingly cleansed and dried afresh, when Thorndyke, having pricked his own thumb with a needle, squeezed out a good-sized drop of blood on to a card.

“There,” said he, with a smile, as he spread the drop out with the needle into a little shallow pool, “it is not every lawyer who is willing to shed his blood in the interests of his client.”

He proceeded to make a dozen prints as before on two cards, writing a number with his pencil opposite each print as he made it.

“We are now,” said he, as he finally cleansed his client’s thumb, “furnished with the material for a preliminary investigation, and if you will now give me your address, Mr. Hornby, we may consider our business concluded for the present.  I must apologise to you, Mr. Lawley, for having detained you so long with these experiments.”

The lawyer had, in fact, been viewing the proceedings with hardly concealed impatience, and he now rose with evident relief that they were at an end.

“I have been highly interested,” he said mendaciously, “though I confess I do not quite fathom your intentions.  And, by the way, I should like to have a few words with you on another matter, if Mr. Reuben would not mind waiting for me in the square just a few minutes.”

“Not at all,” said Reuben, who was, I perceived, in no way deceived by the lawyer’s pretence.  “Don’t hurry on my account; my time is my own ­at present.”  He held out his hand to Thorndyke, who grasped it cordially.

“Good-bye, Mr. Hornby,” said the latter.  “Do not be unreasonably sanguine, but at the same time, do not lose heart.  Keep your wits about you and let me know at once if anything occurs to you that may have a bearing on the case.”

The young man then took his leave, and, as the door closed after him, Mr. Lawley turned towards Thorndyke.

“I thought I had better have a word with you alone,” he said, “just to hear what line you propose to take up, for I confess that your attitude has puzzled me completely.”

“What line would you propose?” asked Thorndyke.

“Well,” said the lawyer, with a shrug of his shoulders, “the position seems to be this:  our young friend has stolen a parcel of diamonds and has been found out; at least, that is how the matter presents itself to me.”

“That is not how it presents itself to me,” said Thorndyke drily.  “He may have taken the diamonds or he may not.  I have no means of judging until I have sifted the evidence and acquired a few more facts.  This I hope to do in the course of the next day or two, and I suggest that we postpone the consideration of our plan of campaign until I have seen what line of defence it is possible to adopt.”  “As you will,” replied the lawyer, taking up his hat, “but I am afraid you are encouraging the young rogue to entertain hopes that will only make his fall the harder ­to say nothing of our own position.  We don’t want to make ourselves ridiculous in court, you know.”

“I don’t, certainly,” agreed Thorndyke.  “However, I will look into the matter and communicate with you in the course of a day or two.”

He stood holding the door open as the lawyer descended the stairs, and when the footsteps at length died away, he closed it sharply and turned to me with an air of annoyance.

“The ‘young rogue,’” he remarked, “does not appear to me to have been very happy in his choice of a solicitor.  By the way, Jervis, I understand you are out of employment just now?”

“That is so,” I answered.

“Would you care to help me ­as a matter of business, of course ­to work up this case?  I have a lot of other work on hand and your assistance would be of great value to me.”

I said, with great truth, that I should be delighted.

“Then,” said Thorndyke, “come round to breakfast to-morrow and we will settle the terms, and you can commence your duties at once.  And now let us light our pipes and finish our yarns as though agitated clients and thick-headed solicitors had no existence.”