"The Professor keeps it on his watch-chain."
"Is it a simple key?"
"No, sir, it is a Chubb's key."
"Very good. Mrs. Marker, you can go. Now we are making a little progress. Our lady enters the room, advances to the bureau, and either opens it or tries to do so. While she is thus engaged, young Willoughby Smith enters the room. In her hurry to withdraw the key, she makes this scratch upon the door. He seizes her, and she, snatching up the nearest object, which happens to be this knife, strikes at him in order to make him let go his hold. The blow is a fatal one. He falls and she escapes, either with or without the object for which she has come. Is Susan, the maid, there? Could anyone have got away through that door after the time that you heard the cry, Susan?"
"No sir, it is impossible
