The narrator of "The Black Cat" introduces the tale by saying the events of his story have terrified him and represent "little but Horror," but he thinks the story may seem quite ordinary to other people. He also claims he is not "mad," or insane, which seems like a red flag from the beginning. Why would a sane man introduce himself by saying he is not insane?
The narrator goes on to describe his childhood. He says he was known for being "docile" and for his particular love of animals. He preferred spending time with pets to being in human company. This information is ironic given what happens later in the story.
He continues by discussing his wife, who has a similar personality to his own. They have numerous pets, including a beautiful black cat named Pluto, who is described as "sagacious to an astonishing degree." The narrator's wife is superstitious about black cats, so the narrator takes care of the cat himself. He and the cat have an intense bond and are nearly inseparable.
Years pass in this way until the narrator becomes an alcoholic. His "intemperance" leads to changes in the narrator's moods and behavior; he notes that he has even mistreated some of their pets, but not the black cat. However, Pluto, who is also growing older, is affected by the narrator's changed demeanor. One night, the narrator comes home drunk and Pluto bites his hand. The narrator describes himself seizing the cat and cutting one of its eyes out. He also explains he felt his old self leave his body, that alcohol supposedly makes him a completely different person.
The cat recovers but fears the narrator. One morning, inspired by what he calls "perverseness" and the knowledge that he is committing a sin, the narrator hangs the cat with a noose. He describes himself as crying and feeling remorseful but also says he committed the act "because I knew that it had loved me." That night, there is a fire at the narrator's house. In the ruins, on one wall, there is an image of a cat hanging from a noose. Although the narrator comes up with a "reasonable" explanation for the phenomenon, he still feels haunted by it.
Later, on another night when the narrator is drunk, a black cat nearly identical to Pluto approaches him. The narrator pets the cat, and it follows him home. The narrator's wife loves the cat, but the narrator soon begins to hate the "beast." He notices the cat is missing an eye, the same eye he cut from Pluto's eye socket. The cat stalks the narrator, who is basically driven to dread and insanity by its attentions.
The narrator's wife repeatedly draws his attention to the patch of white hair that distinguishes this cat from Pluto. The white mark changes over time, eventually becoming what the narrator interprets as an image of his previous crime against Pluto. This puts the narrator over the edge, and he murders his wife in the cellar. He walls her body up in the cellar to hide the evidence of his crime. The narrator looks for the cat for several days in vain. Just when the police come to investigate the missing woman's disappearance, a cat meow can be heard from behind the cellar wall. The narrator accidentally walled the cat in with his wife's body, and the cat exposes him as the murderer.