At the beginning of the story it's in an old man's room in the middle of the night. The narrator says he's not mad just nervous. Then he tells us how calmly he can tell us the story.
The narrator wants to prove us his sanity. For a whole week he's kind to the old man. Then for eight days at midnight he would look in on the man. While he looked in on him he would open the lantern to see if the old mans vulture like eye was open. In the morning the narrator would ask the old man how he sleep to see if he heard anything at night.
On the eighth night the narrator wakes the old man but keeps going to the room. For a hole hour neither for them moved. The narrator open's the lantern and see's the eye. Then the narrator starts to hear a low, dull quick sound and thinks its the old man heart beat. He thinks the noise keeps getting louder. His anxiety make the narrator think the noise will be heard.
"I did it !"
On the eighth night the narrator finds the courage to smother the old man to death. To smother him the narrator used the old mans mattress.
The narrator dismembers the body by cutting it up in the bathtub. To hide the body he puts in under the wood floor. Later the police arrive because a neighbor heard a loud screech. The Police search the house and the narrator invites them in. When they sit down the narrator puts his chair on the boards on top of the body. The narrator starts to hear the old mans heart beat again. Then he flips out because the sound keeps getting louder.
The narrator confesses to the crime because he cant stand the sound of beating heart. the heart beat was his own and was getting faster because of guilt.