The narrator wants to prove he his not crazy, even though he killed a man because of his bionic eye.
The narrator runs into a man with a "deformed eye that looks like a vulture eye" that lives in the same building as him. The narrator is now frightened.
Each night the narrator enters the old mans room and sees his bionic eye. He plots to kill him for the next eight straight days.
One night the old man wakes up and sees the narrator in his room and screams. The narrator knocked the old man off the bed and smothers him with the bed intill he can no longer hear his heart beating.
The neighbor calls the police and they soon arrive claiming they heard a loud scream. The narrator then tries to cover up saying he screamed and the old man is out of town.