The Cask of Amontillado is a psychological, creepy thriller. Perfect for October. Montressor has had his ego wounded badly by Fortunato. Looking for revenge Montressor waits until Fortunato is well in the drink and can be lured away to his death. The entire story is a study in human failings.
Montressor is able to convince Fortunato to come with him because Fortunato cannot bear the idea of another man playing the expert in identifying Montressor's Amontillado wine. Montressor uses this jealousy to spur Fortunato deeper into the catacombs. At the same time Montressor showers Fortunato with concerns for his health in an effort to steer Fortunato away from suspicion. For Fortunato cannot suspect a trap if he is the one insistent on continuing deeper into Montressor's underground chambers.
The reader never does find out what insults Montressor has suffered at the hands of Fortunato. The wrong doing is certainly not as important as the revenge. ( )