In the morning I was awakened by an impatient knocking at my bedroom door. Going to bed at two or three I was naturally a late riser, and this was about nine. I scrambled sleepily out of bed, and turned the key. Hewitt was standing in my sitting-room, with a newspaper in his hand.

"Sorry to break your morning sleep, Brett," he said, "but something interesting has happened in regard to that business you helped me with yesterday, and you may like to know. Crawl back into bed if you like."

But I was already in my dressing-gown, and groping for my clothes. "No, no, come in and tell me," I said. "What is it?"

Hewitt sat on the bed. "I'll tell you in due order," he said. "First, I saw Samuel again last night—after you had gone away. You remember I went back to my office; I had a letter or two to write which I had set aside in the afternoon. Well, I wrote the letters, shut up, and went downstairs. I opened the outer door, and there was Samuel, in the act of ringing the housekeeper's bell. He said he was very anxious, and couldn't sleep without coming to hear if I had made any progress; he had called before, but I was out. I half thought of taking him back to my office, but decided that it wasn't worth while. So I walked along to the corner of the Strand, till I got him well under the lights. Then I stopped and talked to him. 'You ask about the progress in your case, Mr. Samuel,' I said. 'Now, I have sometimes met people who seem to consider me a sort of prophet, seer, or diviner. As a matter of fact, I am nothing but a professional investigator, and even if I were possessed of such an amazing genius as I lay no claim to, I could never succeed in a case, nor even make progress in it, if my client started me with false information, or only told me half the truth. More, when I find that such is the state of affairs, and that if I am to succeed I must begin by investigating my client before I proceed with his case, I throw that case up on the instant—invariably. Do you understand that? Now I must tell you that I have made no progress with your case, none; for that very reason.'"

"He protested, of course—vowed he had told me the simple truth, and so forth. I replied by asking him certain definite questions. First, I asked him whose the diamonds were. He repeated that they were his own. To that I simply replied, 'Good evening, Mr. Samuel,' and turned away. He came after me beseechingly, and prevaricated. He said something about another party having an interest, but the matter being confidential. To that I responded by asking him with whom he had communicated before sending for me, and who was the person in the brougham which he had twice entered. That flabbergasted him. He said that he couldn't answer those questions without bringing other parties into the matter, to which I answered that it was just those other parties that I meant to know about, if I were to move a step in the matter. At this he got into a sad state—imploring, actually imploring, me not to desert him. He said he should do something desperate—something terrible—that night if I didn't relieve his mind, and undertake the case. What he meant he'd do I didn't know, of course, but it didn't move me. I said finally that I would deal only with principals, and that until I had the personal instructions of the actual owner of the diamonds, in addition to a complete explanation of the brougham incident, I should do nothing, and I recommended him to go to the police; and with that I left him."

"And you got nothing more from him than that?"

"Nothing more; but it was something, you see. He admitted, to all intents, that the diamonds were not his own. And now see here. I suppose I left him about ten o'clock. Here is a paragraph in one of this morning's newspapers. It is only in the one paper; the matter seems to have occurred rather late for press."

Hewitt gave me the paper in his hand, pointing to the following paragraph:

"Well," I said, "this certainly seems curious, especially in the matter of the mark on the forehead. But what has it all to do——"

"To do with Samuel and his diamonds, you mean? I'll tell you. That dead man is Denson!"

"Denson?" I exclaimed. "Denson? How?"

"I get it from the housekeeper next door. It seems that when the police came to examine the body they found, among other things—money and a watch, and the like—a piece of an addressed envelope, used to hold a few pins—the pins stuck in and the paper rolled up, you know. There was just enough of it to guess the address by—that of the office next door; and it was the only clue they had. So they came along here at once and knocked up the housekeeper. He went with them and instantly recognised Denson, disguised in labourer's clothes, but Denson, he says, unmistakably."

"And the mark on the forehead?"

"That is very odd. It is an outlined triangle, rather less than an inch along each side. It is quite red, he says, and seems to be done in a greasy, sticky sort of ink or colour."

"Was anything found—the diamonds?"

"No. He says there was money—two or three five-pound notes, I believe, some small change, a watch, keys and so forth; but there's not a word of diamonds."

I paused in my dressing. "Does that mean that the murderer has got them?" I asked. Hewitt pursed his lips and shook his head. "It may mean that," he said, "but does it look altogether like it when five-pound notes are left? On the other hand, there is the disguise; the only reason that we know of for that would be that he was bolting with the diamonds. But the really puzzling thing is the mark on the forehead. Why that? Of course, the picturesque and romantic thing to suppose is that it is the mark of some criminal club or society. But criminal associations, such as exist, don't do silly things like that. When criminals rob and murder, they don't go leaving their tracks behind them purposely—they leave nothing that could possibly draw attention to them if they can help it; also, they don't leave five-pound notes. But I'm off to have a look at that mark. Inspector Plummer is in charge of the case—you remember Plummer, don't you, in the Stanway Cameo case, and two or three others? Well, Plummer is an old friend of mine, and not only am I interested in this matter myself, but now that it becomes a case of murder, I must tell the police all I know, merely as a loyal citizen. I've an idea they will want to ask our friend Mr. Samuel some very serious questions."

"Will you go now?"

"Yes, I must waste no more time. You get your breakfast and look out for me, or for a message."

Hewitt was off to Vine Street, and I devoted myself to my toilet and my breakfast, vastly mystified by this tragic turn in a matter already puzzling enough.

---

It was not a messenger, but Hewitt himself, who came back in less than an hour. "Come," he said, "Plummer is below, and we are going next door, to Denson's office. I've an idea that we may get at something at last. The police are after Samuel hot-foot. They think he should be made sure of in any case without delay; and I must say they have some reason, on the face of it."

We joined Plummer at once—I have already spoken of Plummer in my accounts of several of Hewitt's cases in which I met him—and we all turned into the office next door. There we found a very frightened and bewildered office boy, whom Denson had given a holiday yesterday, after sending him down to Samuel. He had come to his work as usual, only to meet the housekeeper's tale of the murder of his master and the end of his business prospects. He had little or no information to impart. He had only been employed for a month or six weeks, and during that time his work had been practically nothing.

Plummer nodded at this information, and sniffed comprehensively at the office furniture. "I know this sort o' stuff," he said. "This is the way they fit up long firm offices and such. This place was taken for the job, that's plain, by one or both of 'em."

The boy's address was taken, and he was given a final holiday, and asked to send up the housekeeper as he went out. Plummer passed Hewitt a bunch of keys.

The housekeeper entered. "Now, Hutt," said Martin Hewitt, "you were saying yesterday, I think, that the main front door was the only entrance and exit for this building?"

"That's so, sir—the only one as anybody can use, except me."

"Oh! then there is another, then?"

"Well, not exactly to say an entrance, sir. There's a small private door at the back into the court behind, but that's only opened to take in coals and such, and I always have the key. This house isn't like yours, sir; you have no back way into the court as we have. It's a convenience, sometimes."

"Ah, I've no doubt. Do you happen to have the key with you?"

"It's on the bunch hanging up in my box, sir. Shall I fetch it?"

"I should like to see it, if you will."

The housekeeper disappeared, and presently returned with a large bunch of keys.

"This is the one, Mr. Hewitt," he explained, lifting it from among the rest.

Hewitt examined it closely, and then placed beside it one from the bunch Plummer had given him. "It seems you're not the only person who ever had a key exactly like that, Hutt," he said. "See here—this was found in Mr. Denson's pocket."

Plummer nodded sagaciously. "All in the plant," he said. "See—it's brand new; clean as a new pin, and file marks still on it."

"Take us to this back door, Hutt," Hewitt pursued. "We'll try this key. Is there a back staircase?"

There was a small back staircase, leading to the coal-cellars, and only used by servants. Down this we all went, and on a lower landing we stopped before a small door. Hewitt slipped the key in the lock and turned it. The door opened easily, and there before us was the little courtyard which I think I have mentioned in one of my other narratives—the courtyard with a narrow passage leading into the next street.

Martin Hewitt seemed singularly excited. "See there," he said, "that is how Denson left the building without passing the housekeeper's box! And now I'm going to make another shot. See here. This key on Denson's bunch attracted my attention because of its noticeable newness compared with most of the others. Most of the others, I say, because there is one other just as bright—see! This small one. Now, Hutt, do you happen to have a key like that also?"

Hutt turned the key over in his hand and glanced from it to his own bunch. "Why, yes, sir!" he said presently. "Yes, sir! It's the same as the key of the fire-hose cupboards!"

"Does that key fit them all? How many fire-hose cupboards are there?"

"Two on each floor, sir, one at each end, just against the mains. And one key fits the lot."

"Show us the nearest to this door."

A short, narrow passage led to the main ground-floor corridor, where a cupboard lettered "Fire Hose" stood next the main and its fittings. "We have to keep the hose-cupboards locked," the housekeeper explained apologetically, "'cause o' mischievous boys in the offices."

This key fitted as well as the other. A long coil of brown leather hose hung within, and in a corner lay a piece of chamois leather evidently used for polishing the brass fittings. This Hewitt pulled aside, and there beneath it lay another and cleaner piece of chamois leather, neatly folded and tied round with cord. Hewitt snatched it up. He unfastened the cord; he unrolled the leather, which was sewn into a sort of bag or satchel; and when at last he spread wide the mouth of this satchel, light seemed to spring from out of it, for there lay a glittering heap of brilliants!

"What!" cried Plummer, who first got his speech. "Diamonds! Samuel's diamonds!"

"Diamonds, at any rate," replied Hewitt, "whether Samuel's or somebody else's. But they can't have been there long. How often is this cupboard opened?"

"Every Saturday reg'lar, sir," replied the housekeeper; "just to dust it out and see things is right."

"Now, see here!" said Martin Hewitt, "I've had luck in my conjectures as yet, and I'll try again. Here is what I believe has happened. Every word that Samuel told me about the theft of those diamonds was true, except as to their ownership. Denson has planned all along to rob him of as big a collection of diamonds as he could prompt him to get together, and he has played up to this for months. His smaller dealings one way and another were ground-bait. Very artfully he let Samuel take the diamonds safely away once, in order that he should be less watchful and less suspicious the second time. This second time he does the trick exactly as we see. He hangs up the imaginary American's hat, he escapes by the fanlight, and he goes out by the back way to avoid the housekeeper's observation. He has arranged beforehand for this, too. He has seized an opportunity when the housekeeper has been out of his box to get wax impressions of these two keys, and he has made copies of them. And here we come on a curious thing. It is easy enough to understand why he should foresee and get himself a key for the back door, in order to make his escape. But why the key of the hose-cupboard? Why, indeed, should he leave the diamonds behind him at all? It is plain that he meant to come back for them—probably at night. He would have been wholly free from observation in that quiet courtyard, and he could let himself in, get the diamonds, and leave again without exciting the smallest alarm or suspicion. But why take all the trouble? Why not stick to the plunder from the beginning? The plain inference is that he feared somebody or something. He feared being stopped and searched, or he feared being waylaid sometime during yesterday. By whom? There's the puzzle, and I can't see the bottom of it, I confess. If I could, perhaps I might know something of last night's murder.

"As to Samuel's prevarications, there is only one explanation that will fit, now that the rest is made clear. He must have been entrusted with these diamonds by a private owner, for sale—secretly. Some lady of conspicuous position in difficulties, probably—perhaps unknown to her husband. Such things occur every day. A common expedient is to sell the stones and have good paste substituted, in the same settings. Samuel would be just the man to carry through a transaction of that sort. That would account for everything. The jewels are en suite, cut, but unset—taken from a set of jewellery, and paste substituted. Samuel arranges it all for the lady, finds a customer—Denson—who treats him exactly as he has told us. When he realises the loss Samuel doesn't know what to do. He mustn't call the police, being bound to secrecy on the lady's behalf. He sends her a hasty message, and remains keeping watch by Denson's office. She hurries to him with all possible secrecy, keeping her carriage blinds down; he dashes into the brougham to describe the disaster, taking his case with him in his frantic desire to explain things fully. The lady fears publicity, and won't hear of the police—she instructs him to consult me: and consequently, of course, when I recommend communicating with the police he won't listen to the suggestion. Samuel has arranged with the lady to hurry off and report progress as soon as he has consulted me, and this he does, the lady having appointed Manchester Square for the interview. Perhaps she hints some suspicion of Samuel's honesty—rather natural, perhaps, in the circumstances. That terrifies him more than ever, and leads to his frantic appeals to me when I throw the case up. Come, there's my guess at the facts of the case, and I'll back it with twopence and a bit more. Eh, Plummer?"

"I don't take your bet," answered Plummer. "The thing's plain enough; except the murder. There's something deeper there."

Hewitt became grave. "That's true," he said, "and something I can see no way into, as yet. But come—you take this parcel of diamonds, as representing the law. And here comes one of your men, I think."

We had been approaching the front door during this talk, and now a police constable appeared, and saluted Plummer. "Samuel's just been brought in, sir," he reported. "He's half dead with fright, and he's sent a message to Lady H—— in P—— Square; and he says he wants Mr. Martin Hewitt to come and speak for him."

"Poor Samuel!" Hewitt commented. "Come, we'll go and make him happy. Here are the diamonds, and, those safely accounted for, there's no evidence to connect him with the murder. We'll get him out of the mess as soon as possible."

And so they did. Hewitt's reading of the case was correct to a tittle, as it turned out, and with very little delay Samuel was released. But with the message from the police station, the fat was in the fire as regarded Lady H——. Her husband necessarily became acquainted with everything, and there was serious domestic trouble.

Samuel was glad enough to get quit of the business with no worse than a bad fright, as may well be supposed. He showed himself most grateful to Hewitt in after times, giving him excellent confidential advice and information more than once in matters connected with the diamond trade. He is still in business, I believe, in a much larger way, and I have no doubt he is the wiser for his experience, and for the lesson which Hewitt did not forget to rub well in: that it is useless and worse to place a confidential matter in the hands of a man of Hewitt's profession, and at the same time withhold particulars of the case, however unessential they may appear to be.

---

But meantime, on the way to Vine Street I asked Hewitt what led him to suppose that the new key on Denson's bunch fitted a lock in that particular office building.

"Call it a lucky guess, if you like," Hewitt answered; "but as a matter of fact it was prompted by pure common sense. Plummer showed me the things found on the body, and I saw at once that the keys offered the only chance of immediate information. I went through them one by one. There was his latchkey—the key with which he had gone into his lodgings to fetch away the disguise. There was another largish key, equally old—probably the key of his office door. There were other smaller keys, also old—plainly belonging to bags and trunks and drawers and so forth. And then there was the large, perfectly new key. What was that? It was not the key of any bag or drawer, clearly—it was the key of a door—a door with a lever lock. What door? Had Denson some other office? Perhaps he had, but first it was best to begin by trying it on places we were already acquainted with. At once I thought of Denson's disappearance unobserved by the housekeeper. Could this be the key of some private exit from the office building? I resolved to test that conjecture first, and it turned out to be the right one. Being successful so far, of course I turned to the other new key and tried that, as you saw."

"But what of that triangular mark on the man's forehead?"

Martin Hewitt became deeply thoughtful. "That," he said, "is a matter wholly beyond me at present, as indeed is the whole business of the murder. Whether we shall ever know more I can't guess, but the matter is deep—deep and difficult and dark. As to the mark itself, that seems to have been impressed from an engraved stamp of some sort. It is a plain equilateral triangle in red outline, measuring about an inch on each side. It is in a greasy, sticky sort of red ink, which may be smeared, but is very difficult, if not impossible, to rub away. What it means I can't at present conjecture. I have told you my reasons for not thinking it the sign of any gang of criminals. But whose sign is it? Surely not that of some self-constituted punisher of crime? For such a person, with no risk to himself, could have handed Denson over to the police, if he knew of his offence. Can he have been murdered by an accomplice? But he used no accomplice; if one thing is plain in all that story of the stolen diamonds it is that Denson did the thing wholly by himself. Besides, an accomplice would have taken the keys and have gone and secured the diamonds for himself; else why the murder at all? But no keys were taken—nothing was taken, as far as we can tell. And why was the body placed in that conspicuous position? It is pretty certain that the crime cannot have happened where the body was found—somebody must have heard or seen a struggle in such a place as that. As it is, I should say, the body was probably brought quietly to the spot in a cab, or some such conveyance.

"But mystery envelops this crime everywhere. So far as I can see, there is no clue whatever beyond the Red Triangle, which, as yet, I cannot understand. The strangling points to the murder being committed by a powerful man, certainly, and it is a form of crime that may have been perpetrated silently. But beyond that I can see nothing. The apparent motivelessness of the thing makes the mystery all the darker, and the circumstances we are acquainted with, instead of helping us, seem to complicate the puzzle.

"What was it that Denson feared when he left those diamonds behind him, when he might have carried them away? And why should he fear it in daytime and not at night, since it would seem plain that he meant to have returned for the stones at night? Where did he go to disguise himself yesterday—we know it was not in his lodgings—and where has he left the clothes he discarded?"

All these doubts and mysteries were destined to be cleared up, in more or less degree; but it was not till Hewitt and I had witnessed other singular adventures that the answer came to the problem, the real meaning of the Red Triangle was made apparent, and its connection with the theft of Samuel's diamonds grew clear. For indeed the connection proved in the end to be very intimate indeed. Once, a little later, we were allowed to see a shade farther into the mystery, as I shall tell in the proper place; but even then the real secret remained hidden from us till the appointed end.

So ended the case of Samuel's diamonds, so far as concerned Samuel himself and the owner; but the case of the Red Triangle had only begun.

---