The story surrounds the baffling double murder of Madame L'Espanaye and her daughter in the Rue Morgue, a fictional street in Paris. Newspaper accounts of the murder reveal that the mother's throat is so badly cut that her head is barely attached and the daughter, after being strangled, has been stuffed into the chimney. The murder occurs in an inaccessible room on the fourth floor locked from the inside. Neighbors who hear the murder give contradictory accounts, each claiming that he heard the murderer speaking a different language. The speech was unclear; the witnesses say and they admit to not knowing the language they are claiming to have heard.Paris natives Dupin and his friend, the unnamed narrator of the story, read these newspaper accounts with interest. The two live in seclusion and allow no visitors. They have cut off contact with "former associates" and venture outside only at night. "We existed within ourselves alone", the narrator explains. When a man named Adolphe Le Bon has been imprisoned though no evidence exists pointing to his guilt, Dupin is so intrigued that he offers his services to "G–", the prefect of police.Because none of the witnesses can agree on the language the murderer spoke, Dupin concludes they were not hearing a human voice at all. He finds a hair at the scene of the murder that is quite unusual; "this is no human hair", he concludes. Dupin puts an advertisement in the newspaper asking if anyone has lost an "Ourang-Outang". The ad is answered by a sailor who comes to Dupin at his home. The sailor offers a reward for the orangutan's return; Dupin asks for all the information the sailor has about the murders in the Rue Morgue. The sailor reveals that he had been keeping a captive orangutan obtained while ashore in Borneo. The animal escaped with the sailor's shaving straight razor. When he pursued the orangutan, it escaped by scaling a wall and climbing up a lightning rod, entering the apartment in the Rue Morgue through a window.Once in the room, the surprised Madame L'Espanaye could not defend herself as the orangutan attempted to shave her in imitation of the sailor's daily routine and in doing so accidentally slits the woman's throat with the razor. The bloody deed incited it to fury and it squeezed the daughter's throat until she died. The orangutan then became aware of its master's whip, which it feared, and it attempted to hide the body by stuffing it into the chimney. The sailor, aware of the "murder", panicked and fled, allowing the orangutan to escape. The prefect of police, upon hearing this story, mentions that people should mind their own business. Dupin responds that G– is "too cunning to be profound".