The mystery of Denson's death remained a mystery, despite all the police could do. The coroner's jury returned a verdict of "Murder by some person or persons unknown"—which, indeed, was all that could be expected of them; for they had no more before them than the bare fact that the body, disguised in the clothes of a labourer, had been found on the steps near the Duke of York's column, just before midnight, by a police constable. But for the housekeeper's identification, even the name of the victim would have been unknown. The jury certainly wasted some time in idle speculation as to the strange triangular mark found on the forehead, without a speck of evidence to help them; but in the end they returned their verdict, and went home.

But the police knew a little more than the jury, though that little rather confused than helped them. They exercised their judgment at the inquest in withholding all evidence of the theft of diamonds on which the victim had been engaged, the curious particulars of which I have already related. In this they followed their usual course in cases where the evidence withheld could give the jury no help in arriving at their verdict, and at the same time might easily hamper further investigations if revealed. For the theft had been frustrated by Martin Hewitt's exertions, as we have seen, and in any case the thief was now dead and beyond the reach of human punishment. The one matter now remaining for the police was inquiry into the murder of this same thief, and the one object of their exertions the apprehension of the murderer or murderers.

The case, as I have already said, was in the hands of Inspector Plummer, an intelligent officer and an old friend of Hewitt's. A few days' work after the inquest yielded Plummer so little result that he called at Hewitt's office to talk matters over.

"I suppose," Plummer began, "it's no use asking if you've heard anything more of that matter of Denson's murder?"

Hewitt shook his head. "I haven't heard a word," he said. "If I had, it would have come on to you at once. But I hope you've had some luck yourself?"

"Not a scrap; time wasted; and the few off-chance clues I tried have led nowhere, so that I'm where I was at the start. The thing is quite the oddest in all my experience. See how we stand. Here's a man, Denson, who has just pulled off one of the cleverest jewel robberies ever attempted. He so arranges it that he walks safely off with fifteen thousand pounds' worth of diamonds, leaving the victim, Samuel, stuck patiently in an office for an hour or two before he even begins to suspect anything is wrong, and then unable to set the police after him, for the reasons you discovered. But this Denson doesn't carry the plunder off straightway, as he so easily might have done—he conceals it in the very house where the robbery was committed, taking with him a key by aid of which he may return and get it. Why? As you explained, it was probably because he feared somebody—feared being stopped and searched on the day of the robbery—not after, since it was plain he meant to return for his booty at night. Who could this have been, and why did Denson fear him? Mystery number one. Then this Denson is found dead that same night disguised in the clothes of a labourer, in a most conspicuous spot in London—the last place in the world one would expect a murderer to select for depositing his victim's body, for it is evidently not the place where the murder was committed. More, on the forehead there is this extraordinary impressed mark of a Red Triangle. Now, what can all that mean? Robbery, perhaps one thinks. But the body isn't robbed! There are three five-pound notes on it, besides a sovereign or two and some small change, a watch and chain, keys and all the rest of it. Then one guesses at the diamonds. Perhaps it was an accomplice in the robbery, who finds that Denson is about to bolt with the whole lot. But if there's one thing plain in this amazing business it is that Denson had no accomplice; he did the whole thing alone, as you discovered, and he needed no help. More than that, if this were the work of an accomplice why didn't he get the jewels? There were the keys to his hand and he left them! And would such a person actually go out of his way to put the body where it must be discovered at once, instead of concealing it till he could himself get away with the diamonds? Of course not. But there was no accomplice, and it's useless to labour that farther. All these arguments apply equally against the theory that it was the work of some criminal gang. They would have taken all they could get, notes, keys, diamonds and all, and they wouldn't have been so foolish as to exhibit the body with that extraordinary mark; criminal gangs are not such fools as to take unnecessary chances and gratuitously leave tracks behind them, as you know well enough. Well then, there we stand. So far, do you see any more in it than I do?"

Hewitt shook his head. "No," he said, "I can't say I do. All the considerations you have mentioned have already occurred to me. I talked them over, in fact, with my friend Brett. My connection with the case ceased, of course, with the discovery of the jewels, and about the murder I know no more than has been told me. I never saw the body, and so had no opportunity of picking up any overlooked clue; though doubtless you have seen to that. I know not a tittle more than you have just summarised, and on that alone the thing seems mystery pure and unadulterated."

"All there is beyond that was ascertained by the divisional surgeon on examination of the body. The man died from strangulation, as you know, and the natural presumption from that was that the murderer must have been a powerful man. But the surgeon is of the positive opinion—he is certain, in fact—that Denson was strangled with an instrument—a tourniquet."

"A tourniquet?"

"Yes, a surgeon's tourniquet, such as is used to compress a leg or arm and so stop a flow of blood. He considers the marks unmistakable. Now that might point to the murderer being a medical man."

"Conjecturally, yes; though, of course, it justifies nothing more than conjecture."

"Precisely. Well, that was something, but precious little. A tourniquet is a common thing enough—no more than a band with screw fittings, and there was nothing to show that the tourniquet used was any different from a thousand others; and I can see no particular reason why a doctor should commit a murder like this any more than any other man; in which the divisional surgeon agreed with me. And doctor or none, that Red Triangle was altogether unaccounted for. About that, too, by the way, the divisional surgeon told me a little, but a very useless little. The mark was not properly dried, owing to its slightly greasy nature, and although it was almost impossible to remove it wholly, it was possible to scrape off a little of the ink, or colour. Here is a little of it on a paper—quite dried now, of course."

Plummer carefully took from his pocket a small folded paper, unfolded it, and revealed a smaller paper within. On this were two little smears of a bright red colour. "There—that's the stuff," he said. "The surgeon examined it, and he reports it to be rather oddly constituted—so as to bear some affinity of meaning, possibly, to the triangle. For the stuff is a compound of three substances—animal, vegetable and mineral; there is a fine vegetable oil, he says, some waxy preparation, certainly of animal origin, and a mineral—cinnabar: vermilion, in fact. But though there may be some connection between the triangle and the substances representing the three natural kingdoms, it gives nothing practical—nothing to go on."

Martin Hewitt had been closely examining the marks on the paper, and now he answered, "I'm not so sure of that, though, Plummer. I think at least that it gives us another conjecture. I should guess that the man you want, as well as being acquainted with the use of the tourniquet, has at some time travelled in, or to, China."

"Why?"

"Unless I am wider of the mark than usual, this is the pigment used on Chinese seals. A Chinaman's seal acts for his signature on all sorts of documents; it is impressed or printed by hand pressure from a little engraved stone die, precisely as this triangle seems to have been, and the ink or colour is almost always red, compounded of vermilion, wax, and oil of sesamum."

Plummer sat up with a whistle. "Phew! Then it may have been done by a Chinaman!"

Hewitt shrugged his shoulders. "It's possible," he said; "of course, though, the sign, the triangle, is not a Chinese character. As a character, of course it is the Greek Delta. But it may be no character at all. In the signs of the ancient Cabala, the triangle, apex upward as it was in this case, was the symbol of fire; apex downward, it signified water."

Plummer patted the side of his head distractedly. "Heavens!" he said, "don't tell me I'm to search all China, and Greece, and—wherever the cabalistic pundits come from!"

"Well, no," Hewitt answered with a smile. "I think I should, at any rate, begin in this country. I rather think you might make a beginning at Denson. That is what I should do if the case were mine. See if anything can be ascertained of his previous life—probably under another name or names. He may have been in China. Yes, certainly, as we stand at present, I should begin at Denson."

"I think I will," the inspector replied, "though there's precious little to begin on there. I'd like to have you with me on this job, but, of course, that's impossible, since it's purely a police matter. But something, some information, may come your way, and in that case you'll let me know at once, of course."

"Of course I shall—it's a serious matter, as well as a strange one. I wish you all luck!"

Plummer departed to grapple with his difficulties, but in fact it was Hewitt who first heard fresh news of the Red Triangle, and that from a wholly unexpected quarter.

It was, indeed, only two days after Plummer's visit that Kerrett brought into Hewitt's private room the card of the Rev. James Potswood, with a request for a consultation. Mr. Potswood's name was known to Hewitt, as, indeed, it was to many people, as that of a most devoted clergyman, rector of a large parish in north-west London, who devoted not only all his time and personal strength to his work, but also spent every penny of his private income on his parish. It was not a small income that Mr. Potswood spent in this unselfish way, for he came of a wealthy family, and though a good part of his parish was inhabited by well-to-do people, there was quite enough poverty and distress in the poorer quarters to cause this excellent man often to regret that his resources were not even larger. He was a spare active grey-whiskered man of nearly sixty, with prominent and not very handsome features, though his face was full of frank and simple kindliness.

"My errand, Mr. Hewitt," he said, "is of a rather vague, not to say visionary, character, and I doubt if you can help me. But at any rate I will explain the trouble as well as I can. In the first place, am I right in supposing that you were in some way professionally engaged in connection with that extraordinary case of murder a week or so ago—the case in which a man named Denson was found dead on the steps by the Duke of York's column?"

"Yes—and no," Hewitt answered. "I was professionally engaged on a certain matter about which you will not wish me to particularise—since it is the business of a client—and in course of it I came upon the other affair."

"Then before I ask what you know of that mysterious event, Mr. Hewitt, I will tell you my story, so that you may judge whether you are able to reveal anything, or to do anything. Of course, what I say is in the strictest confidence."

"Of course."

"I have a parishioner, a Mr. Jacob Mason, of whom I have seen very little of late years—scarcely anything at all, in fact, till a few days ago. He is fairly well to do, I believe, living a somewhat retired life in a house not far from my rectory. For many years he has laboured at natural science—chemistry in particular—and he has a very excellently fitted laboratory attached to his house. He is a widower, with no children of his own, but his orphan niece, a Miss Creswick, lives under his guardianship. Mr. Mason was never a very regular church-goer, but years ago I saw much more of him than I have of late. I must be perfectly frank with you, Mr. Hewitt, if you are to help me, and therefore I must tell you that we disagreed on points of religion, in such a way that I found it difficult to maintain my former regard for Mr. Mason. He had a curiously fantastic mind, and he was constantly being led to tamper with things that I think are best left alone—what is called spiritualism, for instance, and that horrible form of modern superstition which we hear whispers of at times from the Continent—the alleged devil-propitiation or worship. It was not that he did anything I thought morally wrong, you understand—except that he dabbled. And he was always running after some new thing—animal magnetism, or telepathy, or crystal-gazing, or theosophy, or some one of the score of such things that have an attraction for a mind of that sort. And it was a characteristic of each new enthusiasm with him that it prompted him to try to convert me; and that in such terms—terms often applied to the doctrines of that religion of which I am a humble minister—as I could in nowise permit in my presence. So that our friendly intercourse, though not interrupted by any definite breaking off, fell away to almost nothing. For which reason I was a little surprised to receive a visit from Mr. Mason on the afternoon of the day on which the newspapers printed the report of the finding of the body of Denson. You may remember that only one morning paper mentioned the matter, and that very briefly; but there were full reports in all the evening papers."

"Yes, the discovery was made very late the previous night."

"So I gathered. Well, I was told that Mr. Mason had been shown into my study, and there I found him. He was in an extremely nervous and agitated state, and he had an evening paper in his hand. With scarcely a preliminary word he burst out, 'Have you seen this in the paper? This—this murder? There—there's the report.' And he thrust the paper into my hands.

"I had not seen or heard anything of the matter, in fact, till that moment, and now he gave me little leisure to read the report. He walked up and down the room, nervously clasping his hands, sometimes together, sometimes at his sides, sometimes before him, shaking his head in a shuddering sort of way, and bursting out once or twice as though the words were uncontrollable, 'What ought I to do? What can I do?'

"I looked up from the paper, and he went on, 'Have you read it? It's a murder—a horrid murder. The poor wretched fellow was trying to escape, but he couldn't. It's a murder!'

"'It certainly seems so,' I said. 'But what—did you know this man, Denson?'

"'No, of course not,' Mason replied, 'but there it is, plain enough, and here's another paper with just the same report, but a little shorter.' He pulled the second paper from his pocket. 'I got what different papers I could, but these are the two fullest. It's plain enough it's a brutal murder, isn't it? And the man was a merchant, or an agent, or something, in Portsmouth Street, but he was found in labourer's clothes—proof that he feared it and was trying to escape it; but he couldn't—he couldn't—no! nor anybody. It's awful, awful!'

"'But I don't understand,' I said. 'Won't you sit down?' For Mason continued to pace distractedly about the room. 'What is it you think this unfortunate man was trying to escape? And what am I to do in the matter?'

"He stopped, pressed both hands to his head, and seemed to control himself by a great effort. 'You must excuse me,' he said. 'I'm a bit run down lately, and my nerves are all wrong. I'm talking rather wildly, I'm afraid. I really hardly know why I came to you, except that I haven't a soul I can talk to about—well, about anything, scarcely.'

"He took a chair, and sat for a little while with his head forward on his hand and his eyes directed towards the floor. Then he said, in a musing way, rather as though he was thinking aloud than talking to me, 'You were right, after all, Potswood, and I was a fool to disregard your warnings. I oughtn't to have dabbled—I should have left those things alone.'

"I said nothing, thinking it best not to disturb him, but to leave him free to say what he wanted to say in his own way. He remained quiet for a minute or two more, and then sat up with an appearance of much greater composure. 'You mustn't mind me, Potswood,' he said. 'As I've told you, I'm in a bad state of nerves, and at best I'm an impulsive sort of person, as you know. I needn't have bothered you like this—I came rushing round here without thinking, and if the house had been a bit farther off I should have come to my senses before I reached you. After all, there's nothing so much to disturb one's-self about, and this man—this Denson—may very well have deserved his fate. Don't you think that likely?'

"He added this last question with an involuntary eagerness that scarcely accorded with the indifferent tone with which he had begun. I answered guardedly. I said of course nobody could say what the unhappy man's sins might have been, but that whatever they were they could never justify the fearful sin of murder. 'And,' I added, 'if you know anything of the matter, Mason, or have the smallest suspicion as to who is the guilty person, I'm sure you won't hesitate in your duty.'

"'My duty?' he said. 'Oh yes, of course; my duty. You mean, of course, that any law-abiding citizen who knows of evidence should bring it out. Just so. Of course I haven't any evidence—that paper gave me the first news of the thing.'

"'I think,' I rejoined, 'that anybody who was possessed of even less than evidence—of any suspicion which might lead to evidence—should go at once and place the authorities in possession of all he knows or suspects.'

"'Yes,' he said—very calmly now, though it seemed at cost of a great effort—'so he should; so he should, no doubt, in any ordinary case. But sometimes there are difficulties, you know—great difficulties.' He stopped and looked at me furtively and uneasily. 'A man might fear for his own safety—he might even know that to say what he knew would be to condemn himself to sudden death; and more, perhaps, more. Suppose—it might be, you know—suppose, for instance, a man was placed between the alternatives of neglecting this duty and of breaking a—well an oath, a binding oath of a very serious—terrible—character? An oath, we will say, made previously, without any foreknowledge of the crime?'

"I said that any such oath taken without foreknowledge of the crime could not have contemplated such an event, and that however wrong the taking of such an oath might have been in itself, to assist in concealing such a crime as this murder was infinitely worse—infinitely worse than taking the oath, and infinitely worse than breaking it. Though as to the latter, I repeated that any such engagement made without contemplation or foreknowledge of such a crime would seem to be void in that respect. I went further—much further. I conjured him to make no secret of anything he might know, and not to burden his conscience with complicity—for that was what concealment would amount to—in such a terrible crime. I added some further exhortations which I need not repeat now, and presently his assumed calmness departed utterly, and he became even more agitated than when first he came. He would say nothing further, however, and in the end he went away, saying he would 'think over the matter very seriously.'

"It was quite plain to me that my poor friend was suffering acutely from the burden of some terrible secret, and that in his impulsive way he had rushed to confide in me at the first shock of the news of this murder, and that afterwards his courage had failed him. But I conceived it my duty not to allow such a matter to stand thus. Therefore, giving Mason a few hours for calm consideration, I called on him in the evening. I was told that he was not very well and had gone to bed; he had, however, left a message, in case I should call, to the effect that he would come and see me in the morning. I waited the whole of that next morning and the whole of the afternoon, and saw nothing of him. In the evening urgent parish work took me away, but next morning I called again at Mason's house and saw him. This time he avoided the subject—tried to dodge it, in fact. But I was not to be denied, and the result was another scene of alternate agitation and forced calmness. I will not weary you, Mr. Hewitt, with useless repetition, but I may say that I have seen Mason twice since then without bringing him to any definite resolve. As a matter of fact, I believe that he is restrained from saying anything further by fear—sheer terror. He has even gone so far as to deny absolutely that he knows anything of the matter—and then has contradicted himself a minute afterwards. At last, this morning, I have brought him a degree further. In the last few days I made it my business to acquaint myself, as far as possible, with the exact circumstances of the tragedy, so far as they are known, and in course of my inquiries I saw the housekeeper of the offices next door—the man who identified the body as Denson's. He either could not, or would not, tell me very much, but he did say that you had been working in some way in connection with the case, and that you knew as much of it as anybody. That gave me an idea. This morning I told Mason that not only he, but I also had a duty in respect to this matter, and my duty was to see that nothing in connection with such a crime as this should be hushed up on any consideration or for anybody's fancies. I said that if he liked he need tell me no more, but might take you into consultation professionally, as your client, allowing me first to see you and to assure you that, consistently with his own safety, he was anxious to further the ends of justice. I said that, as your client, your first duty would be to protect him, that your professional practice would keep your mouth absolutely sealed, and that you already knew a good deal about the crime—perhaps more than he suspected. I protested that this seemed to me the very least he could do, and I warned him that if he refused to do even this, I should have to consider whether it was consistent with my character, as a clergyman and a loyal citizen, any longer to conceal the fact that he was keeping back information that might lead to the apprehension of the murderer. This frightened him, and between the fear of the threat and the fear that you might already know more than he suspected, he authorised me—he was even eager about it—to come and see you; always, of course, under a pledge of strict professional secrecy."

"So far your account is quite clear, Mr. Potswood," Hewitt said. "You have done your best, now I must do mine. You wish me to see Mason at once, no doubt?"

"I arranged to bring you to his house, if you were willing and your engagements permitted, at three this afternoon. Will that do? I have been keeping you, I see—it is past one already. Will you lunch with me at my club?"

"With great pleasure—more especially as I have a few questions to ask as we go along. Is it far?"

"Just at this end of Pall Mall—we will walk, if you like."

"Tell me now," said Hewitt as they went, "anything you know about Mr. Mason's habits, family connections, and so forth, as fully and as minutely as you please. Has he any friends connected with China, for instance?"

"China? Why, no, I think not; except—but I'll tell you all I know. Mr. Mason has no family connections, so far as I am aware—at any rate, in London—except his niece, Miss Creswick. She is within a few months of twenty-one, a charming girl, but horribly shut in, for Mason has almost no visitors. Miss Creswick was his sister's daughter; she lost her mother first and then her father, and was left to the guardianship of her uncle. He was also trustee under the will, and he has, I believe, discretion to keep charge of her property, if he thinks fit, till she reaches the age of twenty-five; though in case of his death she is to inherit in the ordinary way, on coming of age. She is a very dutiful and, indeed, an affectionate niece; though I must say he is scarcely fair to her, keeping her, as he does, so completely secluded from the society of young people of her own age. Mere thoughtlessness, I think; he has had no children of his own, his mind is wholly occupied with his science and his fads, and he makes himself a recluse without a thought of the girl. And that brings me to what I was about to say at first, when you asked me if Mr. Mason had any friends connected with China. There is a young doctor—Lawson is his name—some very distant connection of the family, I think, who had a professional appointment of some sort in Shanghai for a year or two, but who is now in London trying to work up a small practice of his own. If you hadn't mentioned China I shouldn't have thought of him, since he never goes to the house now—or, at any rate, is supposed not to go."

"Doesn't go to the house? And why is that?"

"Well, there was a disagreement. What it was I don't quite know, but in the first place it had some connection with some of Mason's experiments—something which Lawson declined to help him with for professional reasons, or else something he declined to do for Lawson, I don't know which. But the thing went further, for, as a matter of fact, there was something between the young people—Lawson is only twenty-eight—and Mason put an end to that. It had been something like a formal engagement, I think, but in the quarrel—Mason was always quarrelling with somebody when he had friends, and that's why he has so few now—in the quarrel things were said that ended in a rupture. Whether young Lawson was fortune-hunting or not I cannot say, but Mason certainly accused him of it, and promised to keep back the girl's money as long as he could. In the meantime Mason declared an end to the engagement, and poor Helen was broken-hearted; for as I have said, she is an affectionate girl, and she hadn't a friend to confide in. But I'm boring you—you don't want to know all these things, surely?"

"On the contrary, I can't possibly know too much, and the particulars can't possibly be too minute. Nine cases out of ten I bring to an issue by means of a triviality. You were saying a little while back that there were almost no visitors at Mr. Mason's house; but you said 'almost,' and that means there are some. Who are they?"

"Very occasionally—rarely, in fact—there are one or two members of learned societies with whom he had been in correspondence, or who are old friends. There is a Professor Hutton and a Dr. Burge, I believe; but they don't appear once in six months; and there is Mr. Everard Myatt, who is more frequent. He does not profess to be a great man of science, but he is interested in chemistry as an amateur, and is, I fancy, a sort of disciple of Mason's. He has noticed a sad difference in Mason just lately, and he even called on me yesterday, though I hardly knew him by sight, in the hope that I would back up his urgent suggestion that Mason should go off for a change and a rest. Beyond these I don't think I know of a single visitor. But here we are at the Megatherium."