«Do you remember how Germont laughed when I said the mystery was difficult for him to solve because it was so simple?» Dupin filled his pipe with tobacco and lit it. «Well, the more I thought about it, the more I realized the police could not find the letter because D'Arcy had not hidden it at all. So I went to visit D'Arcy in his apartment. I took a pair of dark green eyeglasses with me. I explained to him that I was having trouble with my eyes and needed to wear the dark glasses at all times. He believed me. The glasses permitted me to look around the apartment while I seemed only to be talking to him. I paid special attention to a large desk where there were a lot of papers and books. However, I saw nothing suspicious there. After a few minutes, however, I noticed a small shelf over the fireplace. A few postcards and a letter were lying on the shelf. The letter looked very old and dirty. As soon as I saw this letter, I decided it must be the one I was looking for. It must be, even though it was completely different from the one Germont had described. This letter had a large green stamp on it. The address was written in small letters in blue ink. I memorized every detail of the letter while I talked to D'Arcy. Then when he was not looking, I dropped one of my gloves on the floor under my chair.