Revealing mistake: When Norman drives Dukes car into the pond, it's obvious no one is in it.
Psycho III (1986)
1 revealing mistake
Directed by: Anthony Perkins
Starring: Anthony Perkins, Diana Scarwid, Jeff Fahey, Roberta Maxwell
Other mistake: Maureen cuts her wrists with a razor blade. Days later, no bandages or scars.
Norman Bates: Conservative clothes never go out of style.
Trivia: Diana Scarwid ab-libbed the famous opening line, "There is no God!".