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. These extended lunch hours give my boss excess acid. It's Friday anyway - and hot. Well, you could laze around here a while longer.