Mortal is ready to do anything to obtain a divorce from his wife Nadia. To compromise her, he needs to find her a lover. He thinks he has found the ideal candidate in the person of a manly private detective by the name of Robert Arnaud. But the experience gets out of Mortal's control as, on the one hand, Robert and Nadia fall in love for good, and, on the other hand, Robert, assisted by resourceful young Toto, manages to expose Mortal as the jewel thief he is.

A German-language film loosely based on the 1883 operetta Eine Nacht in Venedig (A Night in Venice) by Johann Strauss II. The film was also made into separate Hungarian-language version Egy éj Velencében based on the same screenplay. The two versions were shot simultaneously. The Hungarian version was co-directed by Wiene and Géza von Cziffra and used a separate cast of Hungarian actors. From Wikipedia.