In Edgar Allan Poe's short story "The Cask of Amontillado," Gothic conventions serve to create an atmosphere of terror; however, in Poe's story, it is not preternatural beings that the characters must fear. Instead, the real horror resides in the hearts of human beings themselves. At the end of Poe's gothic tale of revenge served in the niter-filled catacombs of the Montesor family, after the completion of his walling in of his adversary Fortunato who has committed "a thousand insults" against him, the narrator mentions that his "heart grew sick--on account of the dampness of the catacombs." This excuse of the dampness for the narrator's "sickness" is a rationalization of the narrator. For, the narrator's real sense of terror emanates from his comprehension of the real horror that lies within him, the horror of which human beings are capable.
As he has walled in Fortunato whom he has duped into entering the dank and dark catacombs of his family, Montesor contemplates the horrific act that he has committed against a fellow human being in the name of revenge for "a thousand insults." Perhaps he feels sick because he has a tinge of conscience at the last moment as he forces the final stone into position. But, it is more likely that he, like his victim, is terrorized by his act against nature in killing the hapless victim, Fortunato. Like Kurtz of Heart of Darkness, Montesor, too, could utter the words, "Oh, the horror! the horror!"