The Narrator Timeline and Summary

The narrator says he'll tell a story to prove he's sane.
During nights one through eight (of the narrator's story), the narrator spies on the old man while he sleeps.
On the eighth night, the narrator kills the old man, cuts up the body, and hides it.
The narrator hears a knock at the door and finds three policemen who are investigating the complaint of a suspicious neighbor.
The narrator invites them in and shows them around.
Eventually the narrator begins to hear a noise.
The noise grows so loud that the narrator directs the police to the body, and announces that the noise he's hearing is the heartbeat of the murdered old man.