The narrator watches the old man for seven nights. Every night, he watches the old man sleep and takes a long time to put his head in the room.
On the eighth night the narrator slips and wakes the old man. The old man stays up for a while and then the narrator opens the light and it shines the old man's eye, the narrator goes crazy and murders the man.
The police come to the house and the narrator invites them in. They start chatting and he starts to get nervous and starts hearing heartbeats. He finally goes crazy and turns himself in.