"Yes, sir, she must have been a cool hand."
I saw an intent look pass over Holmes's face.
"You say that she must have come back this way?"
"Yes, sir; there is no other."
"On this strip of grass?"
"Certainly, Mr. Holmes."
"Hum! It was a very remarkable performance -- very remarkable. Well, I think we have exhausted the path. Let us go farther. This garden door is usually kept open, I suppose? Then this visitor had nothing to do but to walk in. The idea of murder was not in her mind, or she would have provided herself with some sort of weapon, instead of having to pick this knife off the writing-table. She advanced along this corridor, leaving no traces upon the cocoanut matting. Then she found herself in this study. How long was she there? We have no means of judging."
"Not more than a few minutes, sir. I forgot to tell you that Mrs. Marker, the housekeeper, had been in there tidying not very long before -- about a quarter of an hour, she says."
"Well, that gives us a limit. Our lady enters this room and what does she do? She goes over to the writing-table. What for? Not for anything in the drawers. If there had been anything worth her taking it would surely have been locked up. No; it was for something in that wooden bureau. Halloa! what is that scratch upon the face of it? Just hold a match, Watson. Why did you not tell me of this, Hopkins?"
The mark which he was examining began upon the brass work on the right-hand side of the keyhole, and extended for about four inches, where it had scratched the varnish from the surface.
"I noticed it, Mr. Holmes. But you'll always find scratches round a keyhole."
"This is recent, quite recent. See how the brass shines where it is cut. An old scratch would be the same colour as the surface. Look at it through my lens. There's the varnish, too, like earth on each side of a furrow. Is Mrs. Marker there?"
A sad-faced, elderly woman came into the room.
"Did you dust this bureau yesterday morning?"
"Did you notice this scratch?"
"No, sir, I did not."
"I am sure you did not, for a duster would have swept away these shreds of varnish. Who has the key of this bureau?"
"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. Before I got down the stair I'd have seen anyone in the passage. Besides, the door never opened, for I would have heard it."
"That settles this exit. Then no doubt the lady went out the way she came. I understand that this other passage leads only to the Professor's room. There is no exit that way?"