The spirit of the evil Dr. Mabuse takes over the body of a famous professor. The professor/Dr. Mabuse then begins a new crime wave that terrorizes the city.
While working as an accountant in his uncle's factory, talented young pianist Peter dreams of becoming a famous composer. When he shows his work to a producer, he manages to convince him to give him a chance. From time to time he gets bigger contracts that keep him more and more away from home and his young wife Elisa. When he "discovers" and supports a pretty ballerina in Munich, a rumor starts that he's having an affair. He fails to realize that his marriage is threatened.
During a journey of the "Ceder", the Captain, von Moltmann, disappears. It looks like an accident, but it could also have been murder. Attorney Dr. Burger and superintendent Störensen discover quickly that two of the crewmen hated the Captain: Chief officer Rohlfs suspects an affair between his fianceé Gerda and von Moltmann. Chief engineer Sparkuhl thinks the Captain has seduced his niece, who later committed suicide. The court decides that the Captain has gone overboard without anyone else's "help", but the rumors don't come to an end.