The Rue Morgue Culprit is an APE, as indicated by the 3-letter solution to the crossword. The Rue Morgue Culprit is a character from Edgar Allan Poe's short story 'The Murders in the Rue Morgue'. In the story, a mysterious murderer kills two women in Paris and the police are unable to solve the crime. It is eventually revealed that the murderer is an escaped orangutan, owned by a sailor who had recently returned from the East Indies.