Montresor is the narrator of "the Cask of Amontillado" by Edgar Allan Poe, and he holds a serious grudge against his friend Fortunato. Montresor is intent on getting his revenge against Fortunato for some imagined insult, and to do that he creates an elaborate plan to kill Fortunato.
Montresor is not a sane man but he is clever, and the plan he devises necessitates some creative thinking on his part. First of all, Montresor must hide his feelings of hatred for Fortunato. He does this so successfully that throughout the entire plan, and even at the end, Fortunato has no clue that Montresor wants to kill him.
Second, Montresor chooses Carnival time to enact his plan; this guarantees that Fortunato will not be immediately missed, buying Montresor some time if he needs it. Brilliant.
Third, Montresor must be able to bring Fortunato to his empty house. To do that, he does the simplest and most clever thing he can think of to do during Carnival time:
I had told them [the servants] that I should not return until the morning and had given them explicit orders not to stir from the house. These orders were sufficient, I well knew, to insure their immediate disappearance, one and all, as soon as my back was turned.
It is an ingenious move to tell the servants that he will not be home but he does not want them to go anywhere; it is human nature for them to disobey under such circumstances, and they do.
Next Montresor has to lure Fortunato away from the Carnival festivities. Montresor determines that the only way he can get Fortunato to leave the celebration is to appeal to his pride as a wine connoisseur. Montresor lies and tells Fortunato he has a cask of Amontillado, a nearly impossible feat during Carnival time. When Fortunato is dismissive of the claim, Montressor argues that he needs someone to test it and then suggests Luchesi, Fortunato's rival, should be the one to test the wine. Of course Fortunato does not want to be outdone by his competition, so he insists on going to taste the wine. Every time Fortunato wavers, Montresor mentions Luchesi and that is enough to keep Fortunado moving. It is an ingenious strategy.
Finally, Montresor has to lure Fortunato into the lowest point in his home, the crypt. To do that, he feigns (pretends) concern for Fortunato's health and keeps giving him medicinal draughts of wine. This keeps Fortunato drunk or tipsy enough to keep moving without too many questions or hesitations.
In short, Montresor is successful in developing and executing a clever plan to lure Fortunato to his death; however, it may have been just a bit too clever, since Fortunato never realized why Montresor wanted him dead.