“No reports of any stranger seen?”

“No, sir. Down at the station they are certain that no stranger either came or went yesterday.”

“Have you had inquiries made at inns and lodgings?”

“Yes, sir: there is no one that we cannot account for.”

“Well, it’s only a reasonable walk to Chatham. Anyone might stay there or take a train without being observed. This is the garden path of which I spoke, Mr. Holmes. I’ll pledge my word there was no mark on it yesterday.”

“On which side were the marks on the grass?”

“This side, sir. This narrow margin of grass between the path and the flower-bed. I can’t see the traces now, but they were clear to me then.”

“Yes, yes: someone has passed along,” said Holmes, stooping over the grass border. “Our lady must have picked her steps carefully, must she not, since on the one side she would leave a track on the path, and on the other an even clearer one on the soft bed?”

“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 brasswork 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?”

“Yes, sir.”

“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.”