Pluto — this was the cat’s name — was my favorite pet and playmate. I alone fed him, and he attended me wherever I went about the house. It was even with difficulty that I could prevent him from following me through the streets.

Here the narrator introduces Pluto, explaining why this particular pet out of all the others has such a profound effect on the narrator’s psyche. The narrator has earlier explained that he considers animals more loving and loyal than humans, and this description of Pluto appears to illustrate exactly this principle. Pluto matters so much to the narrator because Pluto loves him best. The narrator’s wife also loves animals, but Pluto still prefers the narrator. Pluto’s loyalty appearing to waver is what ultimately sends the narrator into a spiral because he relies on Pluto’s unconditional love.

Who has not, a hundred times, found himself committing a vile or a silly action, for no other reason than because he knows he should not?

This quotation comes from the narrator’s description of what he calls “the spirit of perversity,” or the desire to do something because it is wrong. The narrator uses this spirit of perversity as an explanation for why he murders Pluto, claiming that the desire to do wrong is a fundamental human trait. The narrator blames perversity as a way of deflecting some of the blame he has for his actions. Whether perversity is a universal human trait or not, the narrator’s mental state, with his inhibitions lowered by alcohol and his worldview becoming more and more self-serving, allows him to act upon this perversity.

It was now, I say, the image of a hideous — of a ghastly thing — of the GALLOWS! — oh, mournful and terrible engine of Horror and of Crime — of Agony and of Death!

The narrator here describes the striking transformation of the white spot on the second black cat’s chest from an indistinct blur into a gallows. The image of the gallows clearly refers to the noose with which the narrator hangs Pluto, a visual reminder of his crime. However, the word gallows, as distinct from a noose, evokes the gallows which execute criminals. Be it the spirit of Pluto or the narrator’s own repressed guilt, something is calling for justice. The narrator is overcome by terror at this image, as shown by the multiple pauses the em-dashes indicate.

Upon its head, with red extended mouth and solitary eye of fire, sat the hideous beast whose craft had seduced me into murder, and whose informing voice had consigned me to the hangman.

This sentence is the final sentence in the story, where the police excavate the wall to find the corpse of the narrator’s wife and the black cat, still alive, perched upon her. If we read this moment symbolically, the narrator, who has projected his feelings of guilt and shame onto the black cat, is not entirely wrong in his assessment. His inability to handle his guilt has made him violent. His guilt causes him to rap on the wall, revealing the cat. Psychologically, the narrator’s deflection of blame is the ultimate result of his alcoholism, which has made him more and more selfish throughout the story.