An unnamed narrator begins this tale of murder and criminal detection with a discussion of the analytic mind. He describes the analyst as driven paradoxically by both intuition and the moral inclination to disentangle what confuses his peers. He adds that the analyst takes delight in mathematical study and in the game of checkers, which allows the calculating individual to practice the art of detection—not only of the moves integral to the game, but also the demeanor of his opponent. The narrator argues, however, that analysis is not merely ingenuity. He states that while the ingenious man may, at times, be analytic, the calculating man is, without fail, always imaginative.

The narrator then describes the circumstances in which he met a man named C. Auguste Dupin. Both men were searching for the same book at an obscure library in the Rue Montmartre, in Paris, and began to converse. Soon, they became friends and decided to share the expenses of a residence together. The narrator then relays an anecdote illustrating Dupin’s brilliant powers of analysis: one night, while walking together, Dupin describes an actor whom the narrator is pondering. Amazed, the narrator asks Dupin to explain his method, and we witness Dupin’s capacity to work backward and observe the importance of seemingly insignificant details in order to reach ingenious conclusions.

Soon thereafter, the narrator and Dupin read newspaper headlines about a horrible murder in the Rue Morgue. One night at three a.m., eight or ten neighbors of Madame L’Espanaye and her daughter, Mademoiselle Camille, wake to shrieks from their fourth-floor apartment. The neighbors hear two voices, then silence. The neighbors and two policemen finally break into the locked apartment to find utter disorder and multiple pieces of evidence of a crime, including a blood-smeared razor, locks of gray human hair, bags of money, and an opened safe. They find no traces of the older woman. However, the noticeable traces of soot in the room lead them to the chimney, where they find the corpse of Mademoiselle Camille. They reason that the murderer must have choked Camille to death and then thrust her body up into the chimney. Expanding the search, the neighbors and police discover the body of Madame L’Espanaye in a courtyard in the rear of the building. They find her badly beaten, with her throat severely cut. When the police move the body, in fact, her head falls off. The 4,000 francs that Madame L’Espanaye had just withdrawn from the bank are still in the apartment, ruling out robbery as a motive for the grisly crime.

The newspaper then recounts the depositions of witnesses concerning the voices they heard. They all agree that they heard two voices: one, a deep Frenchman’s voice; and the other, a higher voice of uncertain ethnic origin, though speculated to be Spanish. The gender of the second speaker is uncertain. The same newspaper reports the findings of the medical examiner, who confirms that Camille died from choking and that Madame L’Espanaye was beaten to death with immense violence, most likely by a club. The evening edition of the paper reports a new development. The police have arrested Adolphe Le Bon, a bank clerk who once did Dupin a favor.

With the arrest of Le Bon, Dupin becomes interested in pursuing the investigation and obtains permission to search the crime scene. Dupin is eager to survey the setting because the newspaper reports portray the apartment as impossible to escape from the inside, which makes the case so mysterious. Dupin suggests that the police have been so distracted by the atrocity of the murder and the apparent lack of motive that, while they have been attentive to what has occurred, they have failed to consider that the present crime could be something that has never occurred before. Producing two pistols, Dupin reveals that he awaits the arrival of a person who will prove his solution to the crime.

Dupin also names those elements of the crime scene that he believes the police have mishandled. For example, the shrill voice remains unidentifiable in its gender and its nationality, but it also cannot be identified as emitting words at all, just sounds. He also explains that the police have overlooked the windows in the apartment, which operate by springs and can be opened from the inside. Though the police believe the windows to be nailed shut, Dupin discovers a broken nail in one window, which only seemed to be intact. Dupin surmises that someone could have opened the window, exited the apartment, and closed the window from the outside without raising suspicion.