In "The Black Cat", what did the second cat (with the patch on his neck) remind the narrator about?The black cat,

The white mark on the second cat takes the shape of the gallows and reminds the narrator of the hanging of the first cat. The gallows is the place where a person is executed by hanging. The narrator actually hung the cat, which he had mutilated by gouging out one eye, from a tree. Being reminded of this perverse act stings his conscience, he begins to be paranoid about the second cat. He believes it is tormenting him.