At the very beginning of The Cask of Amontillado Montresor takes Fortunato down to his families tomb to get Fortunato some Amontillado(expensive wine). Little does Fortunato know he will die soon after entering the tomb.
Before entering the tomb Montresor gives Fortunato a drink to keep him drunk so Fortunato doesnt realize what Montresor is doing.
Now they enter to find the Amontillado but Fortunato insists to keep going on even though he is coughing badly due to how damp the tomb is.
At this point there is no turning back to leave the tomb so Montresor's plan must work now. Fortunato is still coughing but doesn't want to leave. So they continue.
Now Montresor tells Fortunato to go inside this hole and says the Amontillado is at the end. Then Montresor chains Fortunato to the wall. Fortunato doesn't realize what is happening cause he is to drunk to.
In the end Fortunato dies behind a wall that Montresor mason-ed together to keep Fortunato from leaving. The last thing you hear is the bells on Fortunato's hat before he dies. Montresor did all this for revenge because Fortunato disrespected Montresor's family name.