Phoenix-based Marion Crane, who has for ten years worked as an assistant to real estate agent George Lowery, laments the fact she and her divorcé boyfriend, Sam Loomis, can't get married due to money issues, he a penniless hardware store clerk whose debt is a result of having to pay alimony. Marion senses an opportunity when one of Lowery's wealthy clients pays his account with $40,000 cash, Marion who is tasked with taking the money to the bank. Being a Friday afternoon, Marion believes she can slip out of town immediately undetected with the money to join Sam in Fairvale, California where he lives, before Lowery would even suspect that she has absconded with the money the earliest by Monday. Despite a number of close calls, Marion is able to make it to fifteen miles short of Fairvale at the Bates Motel where she stops on the rainy Saturday night. The isolated motel has had little business ever since the state highway was moved. The motel is run by friendly but lonely Norman Bates, who lives with with his invalid mother in the big, old house on the hill overlooking the motel. Although she doesn't meet Mrs. Bates, Marion knows that she is an angry, controlling woman based on an argument she overhears between her and Norman. Norman admits that his mother is mentally mad. That evening, Marion has a change of heart and contemplates returning to Phoenix to return the money. But she never makes it either to Phoenix or Fairvale. As such, several people come looking for her, including Sam - who is suspected of being in cahoots with Marion in stealing the money - Marion's worried sister Lila Crane who is able to convince Lowery not to press charges if Marion returns the money, and a private investigator named Arbogast who was hired by Lowery. At various times, they all make their way to the mysterious Bates Motel, where Mrs. Bates will do whatever required to maintain control of what happens at the motel and within her family.