At the beginning of the story Montresor specifies his problem. He must satisfy all the requirements he describes in order to achieve a complete resolution. This is how he explains the problem:
I must not only punish but punish with impunity. A wrong is unredressed when retribution overtakes its redresser. It is equally unredressed when the avenger fails to make himself felt as such to him who has done the wrong.
Montresor succeeds in luring Fortunato through the crowded streets without being recognized as his companion. He succeeds in getting his victim down into his catacombs. He manages to get Fortunato into the narrow niche and to chain him against the granite wall. Fortunato sobers up quickly when he realizes what is happening. He cries: "For the love of God, Montresor!" This is important because it is the first time Fortunato has called Montresor by name. It shows that one of the requirements for revenge is satisfied: Montresor has made himself "felt as such to him who has done the wrong." It also shows that Fortunato is not in a drunken stupor and unable to understand what is happening to him.
Only one requirement is still to be met. "A wrong is unredressed when retribution overtakes its redresser." Poe must show the reader that Montresor has never been accused of killing Fortunato and has probably never been suspected. Montresor concludes his story with what is the true resolution:
Against the new masonry I re-erected the old rampart of bones. For the half of a century no mortal has disturbed them. In pace requiescat!
The body has not been discovered in fifty years. It will never be discovered. Nobody is looking. Fortunato has been forgotten. Montresor is completely safe. He has fulfilled the requirement he specified at the beginning: "I must not only punish but punish with impunity." He was never suspected because he took such pains to show Fortunato and everyone else that they were the best of friends. Montresor keeps addressing his victim as "My friend," and referring to him as "my friend" and "my poor friend" throughout the narrative. The Latin quotation at the very end, which means "Rest in peace," is not ironic. It is intended to show that Montresor has resolved his problem with such complete success and satisfaction that he has cleansed himself of all the hatred he felt for his victim. He has achieved what is so often described these days as "closure."