The setting takes place in Paris, France. Dupin and our narrator of the story are following the case of the Murders in the Rue Morgue and the reader learns about the witnesses testimonies.
Dupin and the narrator go to the crime scene to investigate the murder of Madame L' Esponye and look for clues.
Adolphe Le Bon is falsely accused and arrested by the police for the murders. Adolhpe had delivered Francs to Madame L' Esponye 3 days prior to the crime.
Dupin finds a man with evidence that reinforces the proof Dupin has, they meet and discuss the clues. We find out the killer is an Orangotang.
The sailor had brought the orangotang to Paris for the purpose of selling it, the orangotang escaped and killed using a razor blade. The sailor feared being blamed for the murders and so he remained silent during the investigation.
The police chief releases Adolphe Le Bon from jail after Dupin explains the sailor's story to him. Dupin feels satisfied with himself for solving the mystery.