Janet Leigh plays Marion Crane, an officeworker who steals a large sum of money from her employer, so she can run off with her lover, Sam (John Gavin). On the way to meet Sam, she stops at the Bates Motel, where she meets a nerdy, young innkeeper (Anthony Perkins), whose hobby is taxidermy and whose relationship with his mother is, well, a bit unusual. The majority of the movie revolves around Sam and Marion's sister (Vera Miles), who go to the Bates Motel after Marion disappears (three guesses what happened to her).
The shower scene isn't as scary as you might expect-mostly because it's hard to be surprised by such a famous scene. There are other scenes in the movie that will make you jump a little more, but overall "Psycho" is more impressive as a well-crafted movie than as a "scary" movie.
How Hitchcock linked together shots from a variety of camera angles and implied the action without truly showing it in the infamous scene makes the movie memorable, but will hardly keep you from bathing.