Walter Mitty is a daydreaming comic book writer with an overprotective mother who likes to imagine himself as a hero experiencing great adventures. His dream becomes true when he accidentally meets a mysterious woman who hands him a little black book. According to her it contains the locations of the Dutch crown jewels hidden since World War II. Soon Mitty finds himself in the middle of a confusing conspiracy and has to admit that being a hero in real life isn't that easy.