In the exposition, the narrator is the antagonist. He tells us he is very nervous and that he is not mad and can tell us the story calmly. The disease the narrator had sharpened his senses. He loves the old man but wants to kill him because of his eye.
i got you now.
The narrator wants to prove his sanity. He is kind to the old man for a whole week (Poe uses suspense by the narrator watching the old man). At midnight he looks in at the old man ( uses personification because the narrator is death stalking the old man). The narrator opens the lantern and wants to see if the old man's eye will open or not. He asks how he slept during the night.
On the eighth night the narrator wakes up the old man by slipping his finger on the lantern. The narrator opens the lantern and sees the old man's eye open. The narrator starts hearing a low, dull, quick sound and it gets louder and louder (symbolism tells us he is increasing anxiety). He thinks its the old man's heartbeat but it is his (using internal conflict). He doesn't want the neighbor to hear the sound and thinks it will be head by them.
The narrator uses the "dead hour of the night" to show foreshadowing. On that night the narrator kills the old man by suffocating him with the mattress.
The narrator dismembers the body in the bathtub and hides the body under the floorboards. The police arrive because the neighbor heard a shriek. He invites the police in to sit and talk and the police search the house. The narrator sits on a chair on top of the body and starts to hear the "old man's heartbeat". The sound gets louder and louder.
The narrator confesses to the police because he can't stand the sound of the heartbeat. He had overwhelming guilt for doing the crime.