Max Müller, an underemployed private detective is asked by his beautiful but secretive client, Ingrid Bergmann to look for her fiancé who is disappeared. With his assistant Larry, Müller 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 Fräulein Schick, Müller´s secretary who is in love with him. Müller solves the case although the entire underworld is after him.