The narrator's first cat, named Pluto, is described as "a remarkably large and beautiful animal, entirely black and sagacious to an astonishing degree." The narrator's wife is so impressed with the cat's sagacity, or wisdom, that she seems to suspect that it could, in accordance with "the ancient popular notion," be the spirit form of a witch. This suggestion of evil is compounded by the significance of the cat's name: Pluto is the name of the Roman god of the underworld.

The narrator's first cat, Pluto, at first follows the narrator everywhere, and the narrator is pleased to reciprocate the cat's love. However, the narrator soon becomes cruel and is seemingly possessed by a spirit of evil. He starts to violently abuse the cat. He cuts one of its eyes from the socket, and he then hangs the cat from the branch of a tree.

When he happens upon the second cat, the narrator notices that, in appearance, it is remarkably similar to Pluto. The second cat is "fully as large as Pluto, and closely resemble[s] him in every respect but one." The one difference between the appearance of Pluto and and the second cat is that the latter has "a large, although indefinite splotch of white, covering nearly the whole region of (its) breast." Pluto, by comparison, was black all over. The second cat also resembles Pluto physically, conspicuously, in that it too has only one eye.

In terms of its behavior, the second cat, like Pluto, at first follows the narrator everywhere. However, whereas Pluto followed its owner lovingly, like a companion, the second cat seems to follow the narrator ominously, like a ghost haunting its victim.

Indeed, the narrator remarks that the second cat would follow him with "a pertinacity...difficult to make the reader comprehend." The implication of the story is that this haunting, stalking pertinacity is because the second cat is a reincarnation of Pluto, returned from the dead to avenge its death.