The falling action and resolution are the final two pieces of a story's dramatic structure, usually following closely after the climax. The falling action begins the process of wrapping up any loose ends that may still exist at the finale of a story, and it is usually a more subdued section than the more-exciting climax that precedes it. The resolution (or denouement) is the final part of a story's structure in which
Conflicts are resolved, creating normality for the characters and a sense of catharsis, or release of tension and anxiety, for the reader. (Wikipedia, Dramatic Structure)
In "The Cask of Amontillado," the climax comes when Montresor surprises Fortunato, staples him to the floor, and procedes to wall the man up. The falling action occurs after Fortunato is securely chained and Montresor painstakingly completes the final tiers of the wall. It includes the maniacal laughter by Fortunato and the two men's final responses. The resolution can be found in the final sentences when the narrator reveals to the reader that he has gotten away with the murder: That Fortunato's remains were never found and that
For the half of a century no mortal has disturbed them. In pace requiescat!