"I must explain to you, Mr.Holmes, that to-morrow is the first day of the examination for the Fortescue Scholarship.I am one of the examiners.My subject is Greek, and the first of the papers consists of a large passage of Greek translation which the candidate has not seen.This passage is printed on the examination paper, and it would naturally be an immense advantage if the candidate could prepare it in advance.For this reason great care is taken to keep the paper secret.
"To-day about three o'clock the proofs of this paper arrived from the printers.The exercise consists of half a chapter of Thucydides.I had to read it over carefully, as the text must be absolutely correct.At four-thirty my task was not yet completed.I had, however, promised to take tea in a friend's rooms, so I left the proof upon my desk.I was absent rather more than an hour.
"You are aware, Mr.Holmes, that our college doors are double -- a green baize one within and a heavy oak one without.
As I approached my outer door I was amazed to see a key in it.
For an instant I imagined that I had left my own there, but on feeling in my pocket I found that it was all right.The only duplicate which existed, so far as I knew, was that which belonged to my servant, Bannister, a man who has looked after my room for ten years, and whose honesty is absolutely above suspicion.
I found that the key was indeed his, that he had entered my room to know if I wanted tea, and that he had very carelessly left the key in the door when he came out.His visit to my room must have been within a very few minutes of my leaving it.