Having stolen a large sum of money, Mary Crane arrives at The Bates Motel on her way to meet her lover. The initial interest is firmly focused on Mary's story and whether she will return the money or not. Norman Bates, the middle-aged motel manager, seems to be quite ordinary, if not slightly odd and somewhat of a drinker, but this could be because of his lonely lifestyle. When Mary shows up at his motel and is murdered, in a totally horrific way, made famous by the film, the interest is shifted onto her killer, which becomes the first major twist in this shocking plot.
Bloch was influenced by some of the horrific practices, which were revealed when multiple murderer, Ed Gein, was caught. The Wisconsin farmer dismembered the bodies of his victims but had kept his mother's body in the house. The idea of having a double identity, of being a "normal" member of the community and yet a crazed psychopath at the same time, was fused into Bloch's novel.
With Psycho, Bloch was reflecting the growing contemporary interest in the complexities of the human mind and the ways in which it can go wrong. This example of the thriller genre marked a move away from concern with horror from external factors to the internal horrors of the mind. The novel gives us far more detailed and, and for that reason, more frightening insight into Norman's psychopathic condition than a film can render and is, in its own medium, just as memorable.
