“When will you come to the Black Museum?”

“At once, if you like.  But before we set out I want to discuss Mr. Okasaki with you.  What sort of person is he?”

“A genuine Jap, small, lively, and oval-faced.  His eyes are like tiny slits in a water melon, and when he laughs his grin goes back to his ears.”

“Really, Winter, I did not credit you with such a fund of picturesque imagery.  Would you know him again?”

“I can’t be certain.  All Japs are very much alike, to my thinking, but if I heard him talk I would be almost sure.  Why do you ask?”

“Because I have been looking up a little information with reference to the Ko-Katana and its uses.  Now, Okasaki is the name of a Japanese town.  Family names almost invariably have a topographical foundation, referring to some village, river, street, or mountain, and there may be thousands of Okasakis.  Then, again, it was the custom some years ago for a man to be called one name at birth, another when he came of age, a third when he obtained some official position, and so on.  For instance, you would be called Spring when you were born, Summer when you were twenty-one, Autumn when you became a policeman, and Winter when you reached your present rank.”

“Oh, Christopher!” cried the detective.  “And if I were made Chief Inspector?”

“Then your title would be ‘Top Dog’ or something of the sort.”

Mr. Winter assimilated the foregoing information with a profound thankfulness that we in England do these things differently.

“Why are you so interested in Mr. Okasaki?” he inquired.

“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.