Ver en Cuevana. Ingmar, a young Swedish architect, is engaged to Monika but, marriage being paradoxically a serious thing in Sweden, he wants to put his future wife to the test. For this purpose, the couple made a trip to France during which Monika saw her former lover, Jean-Pierre, who is now married to Pauline, who assured her husband that, if he cheated on her, he would their marriage is over.