“It’s a lesson to you that you can’t deceive me, Constable MacPherson,” said Lestrade, with dignity. “No doubt you thought that your breach of duty could never be discovered, and yet a mere glance at that drugget was enough to convince me that someone had been admitted to the room. It’s lucky for you, my man, that nothing is missing, or you would find yourself in Queer Street. I’m sorry to have called you down over such a petty business, Mr. Holmes, but I thought the point of the second stain not corresponding with the first would interest you.”

“Certainly, it was most interesting. Has this woman only been here once, constable?”

“Yes, sir, only once.”

“Who was she?”

“Don’t know the name, sir. Was answering an advertisement about typewriting and came to the wrong number⁠—very pleasant, genteel young woman, sir.”