Fortunato insulted Montresor and Montresor made plans to get revenge on him. During the carnival, Montresor ran into Fortunato, and offered to share a bottle of amontillado with him, which was down in the catacombs.
Montresor got Fortunato to go down into the wine vault even though Fortunato was sick.
They kept walking down in the vault, towards the catacombs. Montresor kept suggesting to go back, because Fortunato's cough kept getting worse.
May he rest in peace
When they got to their destination, Montresor chains Fortunato to a niche, and plans to trap him there.
Montresor starts to wall up Fortunato, in the niche, with stones and a mortar.
Montresor put the last stone in place and walks away knowing Fortunato is dead. Montresor got away with his revenge and no one disturbed the vault for a half of a century.