Mild-mannered clerk Leon Dutilleul (Bourvil) is shocked to learn that he possesses the ability to walk through solid objects. His pals try to tell him that the possibilities are endless, but the timid Leon remains wary of his power -- that is, until he makes the acquaintance of Susan (Joan Greenwood), a lovely burglar. Hoping to win her over, he decides to pose as a famous criminal by using his special ability for thieving. However, the police are none to pleased with Leon's magic.