The nightmarish, disturbing film's themes of corruptibility, confused identities, voyeurism, human vulnerabilities and victimization, the deadly effects of money, Oedipal murder, and dark past histories are realistically revealed. The master of suspense skillfully manipulates and guides the audience into identifying with the main character Marion, and then with that character's murderer Norman - voyeuristically implicating the audience with the universal, dark evil forces and secrets present in the film. Marion Crane becomes a secondary MacGuffin after her murder. The film's screenplay by Joseph Stefano was adapted from a novel of the same name by Robert Bloch. Like many of Hitchcock's films, Psycho is so very layered and complex that multiple viewings are necessary to capture all of its subtlety.
Symbolic imagery involving stuffed birds and reflecting mirrors are ever-present.
Although it's one of the most frightening films ever made, it has all the elements of very dark, black comedy. Audiences assumed that something horrible would happen in the first few minutes. Violence is present in only two shocking murder scenes, the first about a third of the way through. The remainder of the horror and suspense is created in the mind of the audience, although the tale does include such taboo topics as transvestism, implied incest, and hints of necrophilia. Sam speaks the first line of dialogue, referring to the uneaten lunch food on the stand - on many levels, she has lost her appetite for their ungratifying relationship and mutual poverty.