The narrator or antagonist tells us he is not mad but just nervous and diseased. He claims that this disease has sharpen his senses. He then says he can tell the whole story calmly, the story that deals with the murder of the old man and his "vulture eye". Even though the old man was nice, the internal conflict was the old man's eye.
The Narrator continues to say he's not crazy. He is kind to the old man the week before he kills him. At midnight he'd look in on the old man. He does this continuously creating suspense. The Narrator would open a lantern to see if the old man's eye was open. The next day he would ask how the old man how he slept. Little did the old man know... Death, in approaching him had stalked with his black shadow before him, and enveloped the victim. The personification in this sentence is foreshadowing the old man's death.
I'm so wise to have dismembered his body here.
On the 8th night at the narrator accidentally wakes up the old man, but continues into his room. The old man sits up in his bed as The Narrator continues into his room. The narrator opens the lantern and sees the old man's eye open... the vulture eye. The narrator then hears a low dull quick sound and thinks it's the old mans heartbeat. The narrator thinks the heartbeat is getting louder and louder. He then has anxiety, thinking the sound will be heard by a neighbor.
So the narrator kills the old man. He kills him by suffocating the old man with his mattress.
The narrator dismembers the old man's body in the bathtub. He then hides the dismembered body underneath the floorboards. A neighbor called the police because they heard a shriek. The police come to the house and the narrator invites them in. The narrator sits on a chair above the old mans body. The narrator starts to hear the old man's heartbeat. It gets louder and louder, as the narrator flips out.
The narrator confesses to the murder of the old man. He confessed because he couldn't stand the sound of the heartbeat, which is symbolism of his own quilt.