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."