A wealthy man murders his wife, then marries a young woman who becomes suspicious of him.

Operetta (German: Operette) is a 1940 musical film directed by Willi Forst and starring Forst, Maria Holst and Dora Komar. The film was made by Wien-Film, a Vienna-based company set up after Austria had been incorporated into Greater Germany following the 1938 Anschluss. It is the first film in director Willi Forst's "Viennese Trilogy" followed by Vienna Blood (1942) and Viennese Girls (1945). The film portrays the life of Franz Jauner (1832–1900), a leading musical figure in the city. It is both an operetta film and a Wiener Film.

After a shady collector of paintings has been murdered, adept Dr. Sebastian Ott discovers a big organised fraud with fake paintings. His twin brother Ludwig is responsible for it, kidnaps him and locks him away in his house. He uses Otts ID and 'replaces' him...

In this convoluted melodrama, an elderly thespian falls for a rising young starlet. He admits his love for her and then announces that he will retire. The young woman pretends she loves him too, but her real motive is to give her struggling lover, also an aspiring actor, a break.