Max Muller, an underemployed private detective is asked by his beautiful but secretive client, Ingrid Bergmann, to look for her fiancé who has disappeared. With his assistant Larry, Muller combs the underworld and meets an attractive but dangerous woman who is the boss of a band. He discovers that the father of his client is also entangled in the affair. There is also a mysterious background, compromising photographs of an important person, murders and Fraulein Schick, Muller's secretary who is in love with him. Muller solves the case although the entire underworld is after him. Musical comedy with slapstick and parodistic citations from well-known classic films of the crime movie genre.