“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. His forgetfulness about the key would have mattered little upon any other occasion, but on this one day it has produced the most deplorable consequences.