Sabine (Ursula Karven) heads off to a sunny holiday resort with her son and her friend, leaving her unsuspecting husband, Andreas, behind at home. While unwinding, she meets Thierry (Bruno Eyron), a handsome, charismatic globetrotter, and gives in to temptation, embarking on a intense summer affair. When the vacation ends, Sabine cuts ties and returns home to resume her stable family life. However, Thierry refuses to be forgotten. He follows her back to Hamburg, systematically manipulating his way into her domestic circle and befriending her completely oblivious husband, turning Sabine's life into a tense, terrifying nightmare as he threatens to dismantle her entire world.