The mood is psychologically disturbing as is made clear by Montresor's choice to sit "down upon the bones" and listen to the lament of Fortunato's "low moaning cry" and the "furious vibrations of the chain":
I laid the second tier, and the third, and the fourth; and then I heard the furious vibrations of the chain. The noise lasted for several minutes, during which, that I might hearken to it with the more satisfaction, I ceased my labours and sat down upon the bones. When at last the clanking subsided, I resumed the trowel,...
The narrator is obviously disturbed, bitter and hateful: "A thousand injuries I had suffered" he exclaims in the opening sentences. Then Montesor gives a psychotic justification for his actions against wrongs that must be redressed and avenged.
With his obsessive hatred he always explains to the reader how well he has prepared his plan. Then, when Fortunato makes the sign of a Mason, Montesor returns with a bizarre movement and laughs, enjoying his sick pun on stone mason. Later, as he gently lures his unsuspecting victim into a dark, narrow recess in the granite catacomb wall, Montesor fetters his victim to the granite rock wall with the steel of chain and padlock.