"The Tell-Tale Heart" is a short story by Edgar Allan Poe. The narrator tells the story of living with a man who had never harmed him, but who had a "cloudy blue eye" that drove the narrator insane—though he insists as he tells the story that he is not insane.
As time passes, the narrator decides that he must kill the old man, but only when his "evil eye" is open. So the narrator sneaks into the old man's bedroom one night, and when the man wakes in terror, the narrator kills him and buries his body beneath the floor boards. The problem the narrator now has is that he can still hear the man's beating heart. It makes him so crazed, that when the police come to investigate the old man's scream, the narrator eventually admits to the deed because he can no longer stand to listen to the beating of the heart...which obviously only exists in his mind.
In the film Psycho, directed by Alfred Hitchcock (an iconic American horror classic), the main character, Norman Bates runs a motel with his mother. When a guest, Marion Crane—a fugitive from the law, having stolen a lot of money—stays over one night, Norman becomes drawn to her.
The most famous scene in the movie is the shower scene where an unknown female assailant stabs Marion to death. When Norman finds out what has happened, he hides all evidence that Marion was ever there.
An investigator for the police, Arbogast, comes to the house to find the missing woman, and he is also stabbed by the unknown female. However, when he does not return, Marion's sister Lila and Marion's boyfriend Sam, who have been working with Arbogast, go to the police. They report having seen Norman's mother in the window, but the police say this is impossible as she had, years before, killed her lover and herself.
Meanwhile, Norman has forced his mother into the fruit cellar so no one will find her. Lila and Sam check into the motel as newlyweds. When Sam confronts Norman, Lila hides in the fruit cellar, where she discovers the mummified corpse of Norman's long-dead mother. Norman knocks Sam unconscious and attempts to kill Lila, dressed in his mother's clothes and a wig. Sam overpowers Norman.
It is discovered that "Norman" has murdered two other women. It was actually Norman who killed his mother and her lover, and in his guilt, he recreated his dead parent in his mind, having developed a multiple-personality disorder. And whenever Norman likes a girl, the "mother" side of his brain murders her out of jealousy.
At the end, Norman is institutionalized, believing he is Mrs. Bates; in his cell he talks in her voice, insisting that her son was the culprit all along, and that she will not be blamed for what he has done.
The similarities are that a man commits murder in both stories. Both men are insane.
The differences are that in Poe's story, the narrator murders one man, and it drives him to admit to what he has done; he is aware of his deed.
In Psycho, Norman Bates murders six people: his mother and her lover, three women, and the investigator. He is unaware of what he has done, burying his mother's murder in his mind, and becoming his mother mentally—sharing his body and psyche with the psyche of his mother.