Although the subject matter of Poe's story is a murder, "The Cask of Amontillado" is not a tale of detection like "The Murders in the Rue Morgue" or "The Purloined Letter"; there is no investigation of Montresor's crime and the criminal himself explains how he committed the murder. The mystery in "The Cask of Amontillado" is in Montresor's motive for murder. Without a detective in the story, it is up to the reader to solve the mystery. From the beginning of the story, it is made clear that Montresor has exaggerated his grievances towards Fortunato. The reader is led to assume that much like his exaggerated grievances, the punishment he chooses will represent what he believes is equal justice, and in turn, going to the extreme.