The grotesque playfulness of the narrator allows Poe to tease out the latent horror of his theme in "The Cask of Amontillado." For instance, Montesor, who has "vowed revenge" states that when he is "accosted with excessive warmth" by Fortunato, he
was so pleased to see him that I thought I should never have done wringing his hand.
As his "own fancy grew warm with the Medoc," Montesor playfully asks Fortunato if he is a mason, waving a trowel in the air as he demonstrates his pun. Continually, Montesor, much like a cat playing and torturing a mouse, feigns concern for Fortunato's health by acting as though they should turn back instead of completing his nefarious plan. But, his gothic arabesques completed, Montesor fetters his victim and walls him in.
Thus, the psychological horror of this tale of revenge parallels the physical is Poe's pattern of "arabesque," as he termed it. The various turnings and returnings in Poe's story develop the horror and cause it to crescendo at the ending with the narrator's perverse "Yes, for the love of God." In a final insanely playful remark Montesor says after he hears the jingling of the unfortunate enemy, "My heart grew sick--on account of the dampness of the catacombs." With no remorse for his act, Montesor proudly states that for a half of a century no one has disturbed Fortunato's tomb' his revenge is complete.
Since the primary themes of "The Cask of Amontillado" are revenge and madness, the emotional makeup of the narrator Montressor certainly seems to fit the bill. He is completely obsessed with his carefully plotted act of revenge upon Fortunato. His sanity has to be questioned, since the unnamed offense seems not to have been equal to the final result, and Montressor takes pleasure in his act of vengeance and in the suffering that Fortunato must endure when he realizes the true nature of the visit to the catacombs. Montressor's cold heart is exposed in his calculating and ruthlessly unsympathetic treatment to his one-time friend.