How does narrator feel immediately after he commits the murder? Do his feeling change? If so how and why?

When the narrator stops hearing the beating of the Old man's heart, he examines the corpse before dismembering it and concealing it beneath the floorboards. He laughs somewhat hysterically as he describes how the tub caught all the blood, leaving no stains on the floor.

By the time he finishes the clean-up, it is four in the morning, and someone knocks on the door. In a cheerful mood, the narrator answers the door only to find three policemen who have come to investigate because a neighbor heard the old man's shriek and alerted the police to the possibility of foul play. The narrator invites them inside, knowing that he has nothing to fear, and he explains that he had been the one to yell as a result of a bad dream and that the old man is currently out visiting the country. He shows the policemen the house and confidently allows them to search it before bringing out chairs which he, in his assurance, places on top of the floorboards that hide the corpse.

The narrator's lack of suspicious behavior convinces the policemen that nothing is wrong, and they sit down on the chairs and chat with him. However, after a while, the narrator begins to wish that the policemen would leave, as his head aches and he hears a ringing in his ears. The ringing increases in volume, for which the narrator compensates by chatting more jovially, but it finally turns into a dull beating which also begins to rise in volume. The narrator becomes more and more agitated in his behavior, gesturing wildly and pacing back and forth, but the policemen hear and suspect nothing.

Soon, the narrator begins to suspect that the pleasantries of the policemen are merely a ruse to ridicule his distress. However, he cannot stand the intensity of the beating and grows tired of what he perceives as the mockery of the policemen. He feels that he "must scream or die," so he finally shrieks the truth, telling the policemen to tear up the floorboards and reveal the beating of the old man's heart.