It is clear that the narrator is Montresor who open the story by stating the he was insulted by his acquaintance, Fortunto, and that he seeks revenge on him. Poe sets the story during the carnival season where he places both characters in costumes. Montresor is dressed in black with a veil which we later find out could signify death. Fortunto is dressed in a colorful jester costume making him seem almost foolish and laughable.
The setting moves to the catacombs beneath the ground where Montresor leads Fortunto to taste a bottle of Amontillado that he has acquired. Along the way they pass the Montresor family remains. The dust from the walk makes Fortunto cough. Montresor offers him some brandy to sooth his cough. By the time they get to their destination, Fortunto is drunk. Montresor chains the drunken Fortunto to a stone and begins to brick him closing off all exits.
Montresor had no concept of law. He had planned this out knowing that he would never be caught. He even sent his servants away to the carnival. In the last few lines of the story it does say that Montresor’s heart grew sick. This could be a small amount of guilt or sympathy but he continues to place the last stone in the new wall he created. The perfect murder.