"I will answer your question by another. Why was he so interested in the Ko-Katana?" "That is hardly what I told you, Mr. Brett. He professed to be interested in the crime itself. But now I come to think of it, he did ask me to let him see the thing." "And did you?" "Yes; I wanted all the information I could get." "My position exactly. Let us go to Scotland Yard." The famous Black Museum has so often been the subject of articles in the public press that no detailed description is needed here. It contains, in glass cases, or hanging on the walls, a weird collection of articles famous in the annals of crime. It is not open to the public, and Brett, who had not seen the place before, examined its relics with much curiosity. The detective exhibited a pardonable pride in some of them, but his companion damped his enthusiasm by saying: "This is a depressing sight." "In what way?" "British rogues are evidently of low intelligence in the average. A bludgeon and a halter make up their history." "There's more than that in a good many cases." "Ah, I forgot the handcuffs." "Well, here is the Ko-Katana," said Winter shortly. The barrister took the fateful weapon, not more deadly than a paper-knife in appearance, and scrutinised it closely. "It has not been cleaned," he said. "No, it was left untouched after the doctor withdrew it from the poor young fellow's breast." Brett produced a magnifying glass. Beneath the rust on the blade he thought he could distinguish some Japanese characters in the quaint pictorial script adapted by that singular people from the Chinese system of writing. He brought the knife nearer to the window and carefully focussed it. Then he produced a note-book and made a pencil drawing of the following inscription: [Illustration] Winter watched him with quiet agony. He had never noticed the signs before. "Mr. Okasaki did not tell you what these scratches meant?" inquired the barrister. "No. He did not see them." "Sure?" "Quite positive. Of course, it is very smart on your part to hit upon them so quickly, but what possible purpose can it serve to find out the meaning of something carved in Japan more than fifty years ago, at the very least?" "I do not know. It is very stupid of me, I admit, but I have not the faintest notion." "Does it make the finding of Okasaki more important?" "To a certain extent. We want to have everything explained. At present we have so little of what I regard as really definite evidence." "May I ask what that little is?" "Sir Alan Hume-Frazer was murdered with a knife produced by a man like David Hume, whom 'Rabbit Jack' saw standing beneath the yews. Not much, eh?" Winter shook his head dubiously. "If Sir Alan were shot instead of stabbed," went on the barrister, "the first thing you would endeavour to determine would be the calibre and nature of the bullet. Why not be equally particular about the knife?"