Pluto is the first cat that the narrator of "The Black Cat" by Edgar Allan Poe owns and claims to have loved. That narrator is obviously not a sane man, but we do get some information from him both about Pluto and the replacement cat which is probably true.
Pluto is "a remarkably large and beautiful animal, entirely black, and sagacious to an astonishing degree." He is the narrator's favorite pet (among many), and the cat follows the narrator everywhere he goes. This proves to be a fatal mistake for Pluto once the narrator begins drinking. Every day the man grows more terrible and mean, and soon his wife and every other animal keep their distance from the cruel and unkind man. Shamefully, Pluto is the only creature the man seems to have any regard for (and that includes his wife), but even that changes after a time.
One night the narrator comes home in a drunken rage and imagines that Pluto is trying to ignore him. In a fury, the man takes a knife and cuts out one of Pluto's eyes. In time the animal heals, but of course he does not trust the man any longer. The spirit of perverseness is strong in the man, however, and everything the cat does not do begins to infuriate him.
One morning, in cool blood, I slipped a noose about its neck and hung it to the limb of a tree;--hung it with the tears streaming from my eyes, and with the bitterest remorse at my heart;--hung it because I knew that it had loved me, and because I felt it had given me no reason of offence;--hung it because I knew that in so doing I was committing a sin--a deadly sin that would so jeopardize my immortal soul as to place it--if such a thing were possible--even beyond the reach of the infinite mercy of the Most Merciful and Most Terrible God.
The man is haunted by this deed and by the image of the cat with a noose about its neck, an image which survives the fire which burned his house after he committed this foul deed.
The narrator continues to drink, and one day he sees another black cat at one of his disreputable drinking spots.
It was a black cat--a very large one--fully as large as Pluto, and closely resembling him in every respect but one. Pluto had not a white hair upon any portion of his body; but this cat had a large, although indefinite splotch of white, covering nearly the whole region of the breast.
The man does not want anything to do with the cat; in fact, just the thought of it causes him great outrage and perturbation. He does not want the cat, but the cat wants him.
This unnamed cat becomes part of the man's family and, like Pluto had done, attaches himself to the man. The narrator is horrified to discover, the next morning, that this cat also has one eye missing. This cat and his fawning grows so detestable to the man that he is constantly enraged at the sight of it.
Even more appalling to the man is the change that happens over time to the white splotch of hair on the new cat's chest, the white spot that was the only difference between this cat and its predecessor both in looks and in deed. The white hairs are now shaped in the form of a gallows, and the man is horrified.
In the rest of the story the man wants to kill the cat, but the cat seems to outwit the man at every turn. In fact, he unknowingly walled the cat into the wall tomb where he placed his dead wife, and it is of course the cat's wailing howls (in addition to the man's arrogant actions) which cause the narrator's foul deed to be discovered.