Before going on leave an experienced magistrate assigns to his assistant a case that has been all but concluded. Everything has been proved. The facts are clear: a brutal murder has been committed. The suspect is a young, beautiful girl, who does not deny or remorse the murder. The only thing that remains to be done is to refer the case to the public prosecutor's office. The case is rather strange though. The murdered man had been a criminal blackmailer; the murderess is a timid girl of 17. The young magistrate tries to discover certain vital truth concealed beneath the obvious facts. The girl has pleaded guilty and the bulk of evidence is against her. The only question that has not been answered concerns the motive of the crime. The detective carefully questions the girl to find her real motives. From her story he learns that the girl is real victim. She arrived from the country and due to her naivety ended up in the apartment of a sexual maniac.
After spending decades living in the shadow of his more famous and successful sibling, Consulting Detective Sigerson Holmes (Wilder) is called upon to help solve a crucial case that leads him on a hilarious trail of false identities, stolen documents secret codes.