Montressor had been insulted by fortunato (friend) previously. Montressor already hated Fortunato so he wanted to kill him. They meeted each other in a carnvial, Fortunato was drunk, so Montressor saw the chance to kill him but he wanted to do in inputy.
Montressor knew Fortunato weakness was wine. So he asked him if if could reassure the amontillado he had purchased was official. Montressor implied that he could ask Luchersi as a way to manipulate Fortunato to go down catacombs in his own will.
As they walked into the catacomb, Montressor noticed Frontunato was sick, so he would cough very often. Montressor would ask Fortunato if he wanted to go back it wasnt to late and he would ask Luchersi. When he would cough Montressor would hand him whiskey to sooth his throat while getting him more drunk.
When they finally reach to the end of the catacomb, Fortunato was full on drunk. They both go into a super small room where Montressor chains him up to the wall. Fortunato believes it is a joke so he laughs.
Montressor begans to stack bricks together. Fortunato begans to sober while he exclaims to Montressor to leave now. Montressor mocks him and wants him to continue crying out.
Montressor then calls out to him to see if he responds to him but does not hear anything. It has be over 50 decades and the body was never found so he had gotten away with murder in a purity way.