The Temple clock had announced in soft and confidential tones that it was a quarter to seven, in which statement it was stoutly supported by its colleague on our mantelpiece, and still there was no sign of Thorndyke. It was really a little strange, for he was the soul of punctuality, and moreover, his engagements were of such a kind as rendered punctuality possible. I was burning with impatience to impart my news to him, and this fact, together with the ghostly proceedings of Polton, worked me up to a state of nervous tension that rendered either rest or thought equally impossible. I looked out of the window at the lamp below, glaring redly through the fog, and then, opening the door, went out on to the landing to listen.

At this moment Polton made a silent appearance on the stairs leading from the laboratory, giving me quite a start; and I was about to retire into the room when my ear caught the tinkle of a hansom approaching from Paper Buildings.

The vehicle drew nearer, and at length stopped opposite the house, on which Polton slid down the stairs with the agility of a harlequin. A few moments later I heard his voice ascending from the hall—

"I do hope, sir, you're not much hurt?"

I ran down the stairs and met Thorndyke coming up slowly with his right hand on Polton's shoulder. His clothes were muddy, his left arm was in a sling, and a black handkerchief under his hat evidently concealed a bandage.

"I am not really hurt at all," Thorndyke replied cheerily, "though very disreputable to look at. Just came a cropper in the mud, Jervis," he added, as he noted my dismayed expression. "Dinner and a clothes-brush are what I chiefly need." Nevertheless, he looked very pale and shaken when he came into the light on the landing, and he sank into his easy-chair in the limp manner of a man either very weak or very fatigued.

"How did it happen?" I asked when Polton had crept away on tip-toe to make ready for dinner.

Thorndyke looked round to make sure that his henchman had departed, and said—

"A queer affair, Jervis; a very odd affair indeed. I was coming up from the Borough, picking my way mighty carefully across the road on account of the greasy, slippery mud, and had just reached the foot of London Bridge when I heard a heavy lorry coming down the slope a good deal too fast, considering that it was impossible to see more than a dozen yards ahead, and I stopped on the kerb to see it safely past. Just as the horses emerged from the fog, a man came up behind and lurched violently against me and, strangely enough, at the same moment passed his foot in front of mine. Of course I went sprawling into the road right in front of the lorry. The horses came stamping and sliding straight on to me, and, before I could wriggle out of the way, the hoof of one of them smashed in my hat—that was a new one that I came home in—and half-stunned me. Then the near wheel struck my head, making a dirty little scalp wound, and pinned down my sleeve so that I couldn't pull away my arm, which is consequently barked all the way down. It was a mighty near thing, Jervis; another inch or two and I should have been rolled out as flat as a starfish."

"What became of the man?" I asked, wishing I could have had a brief interview with him.

"Lost to sight though to memory dear: he was off like a lamplighter. An alcoholic apple-woman picked me up and escorted me back to the hospital. It must have been a touching spectacle," he added, with a dry smile at the recollection.

"And I suppose they kept you there for a time to recover?"

"Yes; I went into dry dock in the O. P. room, and then old Langdale insisted on my lying down for an hour or so in case any symptoms of concussion should appear. But I was only a trifle shaken and confused. Still, it was a queer affair."

"You mean the man pushing you down in that way?"

"Yes; I can't make out how his foot got in front of mine."

"You don't think it was intentional, surely?" I said.

"No, of course not," he replied, but without much conviction, as it seemed to me; and I was about to pursue the matter when Polton reappeared, and my friend abruptly changed the subject.

After dinner I recounted my conversation with Walter Hornby, watching my colleague's face with some eagerness to see what effect this new information would produce on him. The result was, on the whole, disappointing. He was interested, keenly interested, but showed no symptoms of excitement.

"So John Hornby has been plunging in mines, eh?" he said, when I had finished. "He ought to know better at his age. Did you learn how long he had been in difficulties?"

"No. But it can hardly have been quite sudden and unforeseen."

"I should think not," Thorndyke agreed. "A sudden slump often proves disastrous to the regular Stock Exchange gambler who is paying differences on large quantities of unpaid-for stock. But it looks as if Hornby had actually bought and paid for these mines, treating them as investments rather than speculations, in which case the depreciation would not have affected him in the same way. It would be interesting to know for certain."

"It might have a considerable bearing on the present case, might it not?"

"Undoubtedly," said Thorndyke. "It might bear on the case in more ways than one. But you have some special point in your mind, I think."

"Yes. I was thinking that if these embarrassments had been growing up gradually for some time, they might have already assumed an acute form at the time of the robbery."

"That is well considered," said my colleague. "But what is the special bearing on the case supposing it was so?"

"On the supposition," I replied, "that Mr. Hornby was in actual pecuniary difficulties at the date of the robbery, it seems to me possible to construct a hypothesis as to the identity of the robber."

"I should like to hear that hypothesis stated," said Thorndyke, rousing himself and regarding me with lively interest.

"It is a highly improbable one," I began with some natural shyness at the idea of airing my wits before this master of inductive method; "in fact, it is almost fantastic."

"Never mind that," said he. "A sound thinker gives equal consideration to the probable and the improbable."

Thus encouraged, I proceeded to set forth the theory of the crime as it had occurred to me on my way home in the fog, and I was gratified to observe the close attention with which Thorndyke listened, and his little nods of approval at each point that I made.

When I had finished, he remained silent for some time, looking thoughtfully into the fire and evidently considering how my theory and the new facts on which it was based would fit in with the rest of the data. At length he spoke, without, however, removing his eyes from the red embers—

"This theory of yours, Jervis, does great credit to your ingenuity. We may disregard the improbability, seeing that the alternative theories are almost equally improbable, and the fact that emerges, and that gratifies me more than I can tell you, is that you are gifted with enough scientific imagination to construct a possible train of events. Indeed, the improbability—combined, of course, with possibility—really adds to the achievement, for the dullest mind can perceive the obvious—as, for instance, the importance of a finger-print. You have really done a great thing, and I congratulate you; for you have emancipated yourself, at least to some extent, from the great finger-print obsession, which has possessed the legal mind ever since Galton published his epoch-making monograph. In that work I remember he states that a finger-print affords evidence requiring no corroboration—a most dangerous and misleading statement which has been fastened upon eagerly by the police, who have naturally been delighted at obtaining a sort of magic touchstone by which they are saved the labour of investigation. But there is no such thing as a single fact that 'affords evidence requiring no corroboration.' As well might one expect to make a syllogism with a single premise."

"I suppose they would hardly go so far as that," I said, laughing.

"No," he admitted. "But the kind of syllogism that they do make is this—

"'The crime was committed by the person who made this finger-print.

"'But John Smith is the person who made the finger-print.

"'Therefore the crime was committed by John Smith.'"

"Well, that is a perfectly good syllogism, isn't it?" I asked.

"Perfectly," he replied. "But, you see, it begs the whole question, which is, 'Was the crime committed by the person who made this finger-print?' That is where the corroboration is required."

"That practically leaves the case to be investigated without reference to the finger-print, which thus becomes of no importance."

"Not at all," rejoined Thorndyke; "the finger-print is a most valuable clue as long as its evidential value is not exaggerated. Take our present case, for instance. Without the thumb-print, the robbery might have been committed by anybody; there is no clue whatever. But the existence of the thumb-print narrows the inquiry down to Reuben or some person having access to his finger-prints."

"Yes, I see. Then you consider my theory of John Hornby as the perpetrator of the robbery as quite a tenable one?"

"Quite," replied Thorndyke. "I have entertained it from the first; and the new facts that you have gathered increase its probability. You remember I said that four hypotheses were possible: that the robbery was committed either by Reuben, by Walter, by John Hornby, or by some other person. Now, putting aside the 'some other person' for consideration only if the first three hypotheses fail, we have left, Reuben, Walter, and John. But if we leave the thumb-print out of the question, the probabilities evidently point to John Hornby, since he, admittedly, had access to the diamonds, whereas there is nothing to show that the others had. The thumb-print, however, transfers the suspicion to Reuben; but yet, as your theory makes evident, it does not completely clear John Hornby. As the case stands, the balance of probabilities may be stated thus: John Hornby undoubtedly had access to the diamonds, and therefore might have stolen them. But if the thumb-mark was made after he closed the safe and before he opened it again, some other person must have had access to them, and was probably the thief.

"The thumb-mark is that of Reuben Hornby, a fact that establishes a prima facie probability that he stole the diamonds. But there is no evidence that he had access to them, and if he had not, he could not have made the thumb-mark in the manner and at the time stated.

"But John Hornby may have had access to the previously-made thumb-mark of Reuben, and may possibly have obtained it; in which case he is almost certainly the thief.

"As to Walter Hornby, he may have had the means of obtaining Reuben's thumb-mark; but there is no evidence that he had access either to the diamonds or to Mr. Hornby's memorandum block. The prima facie probabilities in his case, therefore, are very slight."

"The actual points at issue, then," I said, "are, whether Reuben had any means of opening the safe, and whether Mr. Hornby ever did actually have the opportunity of obtaining Reuben's thumb-mark in blood on his memorandum block."

"Yes," replied Thorndyke. "Those are the points—with some others—and they are likely to remain unsettled. Reuben's rooms have been searched by the police, who failed to find any skeleton or duplicate keys; but this proves nothing, as he would probably have made away with them when he heard of the thumb-mark being found. As to the other matter, I have asked Reuben, and he has no recollection of ever having made a thumb-mark in blood. So there the matter rests."

"And what about Mr. Hornby's liability for the diamonds?"

"I think we may dismiss that," answered Thorndyke. "He had undertaken no liability and there was no negligence. He would not be liable at law."

After my colleague retired, which he did quite early, I sat for a long time pondering upon this singular case in which I found myself involved. And the more I thought about it the more puzzled I became. If Thorndyke had no more satisfactory explanation to offer than that which he had given me this evening, the defence was hopeless, for the court was not likely to accept his estimate of the evidential value of finger-prints. Yet he had given Reuben something like a positive assurance that there would be an adequate defence, and had expressed his own positive conviction of the accused man's innocence. But Thorndyke was not a man to reach such a conviction through merely sentimental considerations. The inevitable conclusion was that he had something up his sleeve—that he had gained possession of some facts that had escaped my observation; and when I had reached this point I knocked out my pipe and betook myself to bed.

CHAPTER IX
THE PRISONER

On the following morning, as I emerged from my room, I met Polton coming up with a tray (our bedrooms were on the attic floor above the laboratory and workshop), and I accordingly followed him into my friend's chamber.

"I shan't go out to-day," said Thorndyke, "though I shall come down presently. It is very inconvenient, but one must accept the inevitable. I have had a knock on the head, and, although I feel none the worse, I must take the proper precautions—rest and a low diet—until I see that no results are going to follow. You can attend to the scalp wound and send round the necessary letters, can't you?"

I expressed my willingness to do all that was required and applauded my friend's self-control and good sense; indeed, I could not help contrasting the conduct of this busy, indefatigable man, cheerfully resigning himself to most distasteful inaction, with the fussy behaviour of the ordinary patient who, with nothing of importance to do, can hardly be prevailed upon to rest, no matter how urgent the necessity. Accordingly, I breakfasted alone, and spent the morning in writing and despatching letters to the various persons who were expecting visits from my colleague.

Shortly after lunch (a very spare one, by the way, for Polton appeared to include me in the scheme of reduced diet) my expectant ear caught the tinkle of a hansom approaching down Crown Office Row.

"Here comes your fair companion," said Thorndyke, whom I had acquainted with my arrangements, "Tell Hornby, from me, to keep up his courage, and, for yourself, bear my warning in mind. I should be sorry indeed if you ever had cause to regret that you had rendered me the very valuable services for which I am now indebted to you. Good-bye; don't keep her waiting."

I ran down the stairs and came out of the entry just as the cabman had pulled up and flung open the doors.

"Holloway Prison—main entrance," I said, as I stepped up on to the footboard.

"There ain't no back door there, sir," the man responded, with a grin; and I was glad that neither the answer nor the grin was conveyed to my fellow-passenger.

"You are very punctual, Miss Gibson," I said. "It is not half-past one yet."

"Yes; I thought I should like to get there by two, so as to have as long a time with him as is possible without shortening your interview."

I looked at my companion critically. She was dressed with rather more than her usual care, and looked, in fact, a very fine lady indeed. This circumstance, which I noted at first with surprise and then with decided approbation, caused me some inward discomfort, for I had in my mind a very distinct and highly disagreeable picture of the visiting arrangements at a local prison in one of the provinces, at which I had acted temporarily as medical officer.

"I suppose," I said at length, "it is of no use for me to re-open the question of the advisability of this visit on your part?"

"Not the least," she replied resolutely, "though I understand and appreciate your motive in wishing to do so."

"Then," said I, "if you are really decided, it will be as well for me to prepare you for the ordeal. I am afraid it will give you a terrible shock."

"Indeed?" said she. "Is it so bad? Tell me what it will be like."

"In the first place," I replied, "you must keep in your mind the purpose of a prison like Holloway. We are going to see an innocent man—a cultivated and honourable gentleman. But the ordinary inmates of Holloway are not innocent men; for the most part, the remand cases on the male side are professional criminals, while the women are either petty offenders or chronic inebriates. Most of them are regular customers at the prison—such is the idiotic state of the law—who come into the reception-room like travellers entering a familiar hostelry, address the prison officers by name and demand the usual privileges and extra comforts—the 'drunks,' for instance, generally ask for a dose of bromide to steady their nerves and a light in the cell to keep away the horrors. And such being the character of the inmates, their friends who visit them are naturally of the same type—the lowest outpourings of the slums; and it is not surprising to find that the arrangements of the prison are made to fit its ordinary inmates. The innocent man is a negligible quantity, and no arrangements are made for him or his visitors."

"But shall we not be taken to Reuben's cell?" asked Miss Gibson.

"Bless you! no," I answered; and, determined to give her every inducement to change her mind, I continued: "I will describe the procedure as I have seen it—and a very dreadful and shocking sight I found it, I can tell you. It was while I was acting as a prison doctor in the Midlands that I had this experience. I was going my round one morning when, passing along a passage, I became aware of a strange, muffled roar from the other side of the wall.

"'What is that noise?' I asked the warder who was with me.

"'Prisoners seeing their friends,' he answered. 'Like to have a look at them, sir?'

"He unlocked a small door and, as he threw it open, the distant, muffled sound swelled into a deafening roar. I passed through the door and found myself in a narrow alley at one end of which a warder was sitting. The sides of the alley were formed by two immense cages with stout wire bars, one for the prisoners and the other for the visitors; and each cage was lined with faces and hands, all in incessant movement, the faces mouthing and grimacing, and the hands clawing restlessly at the bars. The uproar was so terrific that no single voice could be distinguished, though every one present was shouting his loudest to make himself heard above the universal din. The result was a very strange and horrid illusion, for it seemed as if no one was speaking at all, but that the noise came from outside, and that each one of the faces—low, vicious faces, mostly—was silently grimacing and gibbering, snapping its jaws and glaring furiously at the occupants of the opposite cage. It was a frightful spectacle. I could think of nothing but the monkey-house at the Zoo. It seemed as if one ought to walk up the alley and offer nuts and pieces of paper to be torn to pieces."

"Horrible!" exclaimed Miss Gibson. "And do you mean to say that we shall be turned loose into one of these cages with a herd of other visitors?"

"No. You are not turned loose anywhere in a prison. The arrangement is this: each cage is divided by partitions into a number of small boxes or apartments, which are numbered. The prisoner is locked in one box and his visitor in the corresponding box opposite. They are thus confronted, with the width of the alley between them; they can see one another and talk but cannot pass any forbidden articles across—a very necessary precaution, I need hardly say."

"Yes, I suppose it is necessary, but it is horrible for decent people. Surely they ought to be able to discriminate."

"Why not give it up and let me take a message to Reuben? He would understand and be thankful to me for dissuading you."

"No, no," she said quickly; "the more repulsive it is the greater the necessity for me to go. He must not be allowed to think that a trifling inconvenience or indignity is enough to scare his friends away. What building is that ahead?"

We had just swung round from Caledonian Road into a quiet and prosperous-looking suburban street, at the end of which rose the tower of a castellated building.

"That is the prison," I replied. "We are looking at it from the most advantageous point of view; seen from the back, and especially from the inside, it is a good deal less attractive."

Nothing more was said until the cab drove into the courtyard and set us down outside the great front gates. Having directed the cabman to wait for us, I rang the bell and we were speedily admitted through a wicket (which was immediately closed and locked) into a covered court closed in by a second gate, through the bars of which we could see across an inner courtyard to the actual entrance to the prison. Here, while the necessary formalities were gone through, we found ourselves part of a numerous and very motley company, for a considerable assemblage of the prisoners' friends was awaiting the moment of admission. I noticed that my companion was observing our fellow-visitors with a kind of horrified curiosity, which she strove, however, and not unsuccessfully, to conceal; and certainly the appearance of the majority furnished eloquent testimony to the failure of crime as a means of worldly advancement. Their present position was productive of very varied emotions; some were silent and evidently stricken with grief; a larger number were voluble and excited, while a considerable proportion were quite cheerful and even inclined to be facetious.

At length the great iron gate was unlocked and our party taken in charge by a warder, who conducted us to that part of the building known as "the wing"; and, in the course of our progress, I could not help observing the profound impression made upon my companion by the circumstance that every door had to be unlocked to admit us and was locked again as soon as we had passed through.

"It seems to me," I said, as we neared our destination, "that you had better let me see Reuben first; I have not much to say to him and shall not keep you waiting long."

"Why do you think so?" she asked, with a shade of suspicion.

"Well," I answered, "I think you may be a little upset by the interview, and I should like to see you into your cab as soon as possible afterwards."

"Yes," she said; "perhaps you are right, and it is kind of you to be so thoughtful on my account."

A minute later, accordingly, I found myself shut into a narrow box, like one of those which considerate pawnbrokers provide for their more diffident clients, and in a similar, but more intense, degree, pervaded by a subtle odour of uncleanness. The woodwork was polished to an unctuous smoothness by the friction of numberless dirty hands and soiled garments, and the general appearance—taken in at a glance as I entered—was such as to cause me to thrust my hands into my pockets and studiously avoid contact with any part of the structure but the floor. The end of the box opposite the door was closed in by a strong grating of wire—excepting the lower three feet, which was of wood—and looking through this, I perceived, behind a second grating, Reuben Hornby, standing in a similar attitude to my own. He was dressed in his usual clothes and with his customary neatness, but his face was unshaven and he wore, suspended from a button-hole, a circular label bearing the characters "B.31"; and these two changes in his exterior carried with them a suggestiveness as subtle as it was unpleasant, making me more than ever regretful that Miss Gibson had insisted on coming.

"It is exceedingly good of you, Dr. Jervis, to come and see me," he said heartily, making himself heard quite easily, to my surprise, above the hubbub of the adjoining boxes; "but I didn't expect you here. I was told I could see my legal advisers in the solicitor's box."

"So you could," I answered. "But I came here by choice because I have brought Miss Gibson with me."

"I am sorry for that," he rejoined, with evident disapproval; "she oughtn't to have come among these riff-raff."

"I told her so, and that you wouldn't like it, but she insisted."

"I know," said Reuben. "That's the worst of women—they will make a beastly fuss and sacrifice themselves when nobody wants them to. But I mustn't be ungrateful; she means it kindly, and she's a deuced good sort, is Juliet."

"She is indeed," I exclaimed, not a little disgusted at his cool, unappreciative tone; "a most noble-hearted girl, and her devotion to you is positively heroic."

The faintest suspicion of a smile appeared on the face seen through the double grating; on which I felt that I could have pulled his nose with pleasure—only that a pair of tongs of special construction would have been required for the purpose.

"Yes," he answered calmly, "we have always been very good friends."

A rejoinder of the most extreme acidity was on my lips. Damn the fellow! What did he mean by speaking in that supercilious tone of the loveliest and sweetest woman in the world? But, after all, one cannot trample on a poor devil locked up in a jail on a false charge, no matter how great may be the provocation. I drew a deep breath, and, having recovered myself, outwardly at least, said—

"I hope you don't find the conditions here too intolerable?"

"Oh, no," he answered. "It's beastly unpleasant, of course, but it might easily be worse. I don't mind if it's only for a week or two; and I am really encouraged by what Dr. Thorndyke said. I hope he wasn't being merely soothing."

"You may take it that he was not. What he said, I am sure he meant. Of course, you know I am not in his confidence—nobody is—but I gather that he is satisfied with the defence he is preparing."

"If he is satisfied, I am," said Reuben, "and, in any case, I shall owe him an immense debt of gratitude for having stood by me and believed in me when all the world—except my aunt and Juliet—had condemned me."

He then went on to give me a few particulars of his prison life, and when he had chatted for a quarter of an hour or so, I took my leave to make way for Miss Gibson.

Her interview with him was not as long as I had expected, though, to be sure, the conditions were not very favourable either for the exchange of confidences or for utterances of a sentimental character. The consciousness that one's conversation could be overheard by the occupants of adjacent boxes destroyed all sense of privacy, to say nothing of the disturbing influence of the warder in the alley-way.

When she rejoined me, her manner was abstracted and very depressed, a circumstance that gave me considerable food for reflection as we made our way in silence towards the main entrance. Had she found Reuben as cool and matter-of-fact as I had? He was assuredly a very calm and self-possessed lover, and it was conceivable that his reception of the girl, strung up, as she was, to an acute pitch of emotion, might have been somewhat in the nature of an anticlimax. And then, was it possible that the feeling was on her side only? Could it be that the priceless pearl of her love was cast before—I was tempted to use the colloquial singular and call him an "unappreciative swine!" The thing was almost unthinkable to me, and yet I was tempted to dwell upon it; for when a man is in love—and I could no longer disguise my condition from myself—he is inclined to be humble and to gather up thankfully the treasure that is rejected of another.

I was brought up short in these reflections by the clank of the lock in the great iron gate. We entered together the gloomy vestibule, and a moment later were let out through the wicket into the courtyard; and as the lock clicked behind us, we gave a simultaneous sigh of relief to find ourselves outside the precincts of the prison, beyond the domain of bolts and bars.

I had settled Miss Gibson in the cab and given her address to the driver, when I noticed her looking at me, as I thought, somewhat wistfully.

"Can't I put you down somewhere?" she said, in response to a half-questioning glance from me.

I seized the opportunity with thankfulness and replied—

"You might set me down at King's Cross if it is not delaying you;" and giving the word to the cabman, I took my place by her side as the cab started and a black-painted prison van turned into the courtyard with its freight of squalid misery.

"I don't think Reuben was very pleased to see me," Miss Gibson remarked presently, "but I shall come again all the same. It is a duty I owe both to him and to myself."

I felt that I ought to endeavour to dissuade her, but the reflection that her visits must almost of necessity involve my companionship, enfeebled my will. I was fast approaching a state of infatuation.

"I was so thankful," she continued, "that you prepared me. It was a horrible experience to see the poor fellow caged like a wild beast, with that dreadful label hanging from his coat; but it would have been overwhelming if I had not known what to expect."

As we proceeded, her spirits revived somewhat, a circumstance that she graciously ascribed to the enlivening influence of my society; and I then told her of the mishap that had befallen my colleague.

"What a terrible thing!" she exclaimed, with evidently unaffected concern. "It is the merest chance that he was not killed on the spot. Is he much hurt? And would he mind, do you think, if I called to inquire after him?"

I said that I was sure he would be delighted (being, as a matter of fact, entirely indifferent as to his sentiments on the subject in my delight at the proposal), and when I stepped down from the cab at King's Cross to pursue my way homewards, there already opened out before me the prospect of the renewal of this bitter-sweet and all too dangerous companionship on the morrow.