Berlin journalist Lydia is in a relationship with author Karl-Heinz. Lydia breaks up with Karl-Heinz, but shortly afterwards Sarah moves into her flat, and Karl-Heinz promptly falls in love with her. Lydia meets Walter at a party. Together the four of them go on a trip to the countryside, and Lydia likes it so much that she decides she would like to stay at the farm for a while. After the other three have left, Lydia receives an unexpected visitor. Marquard Bohm stands at her door with a cross, claiming to be Jesus Christ. Marquard Bohm's appearance in this film is considered to be one of the most whimsical guest appearances in German film history. Rudolf Thome's playful comedy "Das Geheimnis" ("Secret of Love") talks about relationships, and explains the secret of the universe along the way.