In Edgar Allan Poe's short story The Tell Tale Heart, the narrator's sanity is repeatedly called into question. The narrator is responsible for taking care of an old man who has a filmy, clouded eye. Haunted by this "vulture-like" eye, the narrator resolves to murder the old man in his sleep. Every night, the narrator creeps into the old man's bedroom and attempts to muster the will to kill him, but because the old man's filmy eye is closed, the narrator is unable to commit the murder. Finally, on the eighth night, the old man awakens. After catching a glimpse of the "Evil Eye," the narrator suffocates the old man and hides the body under the floorboards of the bedroom.
After the narrator conceals the body, the police knock at the door. They inform the narrator that a neighbor reported a scream coming from the house. Confident that the police will not suspect his crime, the narrator invites them in for a tour of the house. As the police enjoy a cup of tea in the old man's bedroom, the narrator begins to hear a noise that he believes is the old man's heart beating from beneath the floorboards. The noise intensifies, and the narrator grows frantic. Although the police act as though they hear nothing, the narrator becomes convinced that they are mocking his terror. The narrator's paranoia overcomes him, and he confesses the murder.