The Purloined Letter ; By Edgar Allan Poe

The narrator and his friend Dupin, from The Murders in the Rue Morgue, get another visit from the Prefect of police. He explains that the Minister D___ has stolen a letter from the royal lady, which he has been using to blackmail her.

The Prefect explains how thoroughly the police has searched the Minister’s apartment, but has found nothing. Dupin tells him to search again and the Prefect goes away disappointed.

 The next month, he comes back. He has performed another search but still found nothing. He admits that he will personally pay a lot of money to have the letter brought to him. Dupin surprises everybody by asking the Prefect to write him a check, and promises to produce the letter, which he does.

The Prefect rushes off to get his own reward from the royal lady, while Dupin explains to the narrator how he got the letter. He went to the Minister’s apartment in a pair of dark glasses and pretended to keep up conversation while he looked around, operating with the suspicion that the Minister has hidden the letter by not actually hiding it at all. 

 Eventually he spots it, a letter right on the Minister's desk that has been turned inside out. Dupin distracts the Minister, pockets the letter, and replaces it with a copy that contains a message from Dupin to the Minister. It turns out the Minister once wronged Dupin, and the message is a quote, warning that the first insult is always remembered.