Montresor gets mad at Fortunato for calling him names in public. Montresor sees Fortunato at the circus and Forunato is drunk dressed as a jester so, Montresor is trying to lead him to his house. (Fortunato loves wine)
Fortunato goes to Montraso's house and sees a huge barrel of wine and two glasses. His house is also empty because he h as let his staff off for the night so it´s just them for the night.
Montresor is leading Fortunato into a catacomb under his house. They go deep into the catacomb and Fortunato is too drunk to even realize what is happening. They go deep into the catacombs and come up on a hole where Montresor pushes Fortunato into the hole.
He buries him in the alive in the hole and walks out like nothing has happened.
He lives his life normally as if nothing had ever happened.