The robber knight Ratzfatz instills fear and terror throughout the region. Together with his companions, he ambushes trade caravans and robs coaches. Gundis, the daughter of Baldur von Beulenstein, has heard much about the notorious robber knight. One day, while eavesdropping on a conversation between Baldur and two other knights, she learns that none other than her father is the robber knight Ratzfatz. Now she understands why he always returns so battered from his "tournaments." On the next raid, Baldur brings home a captured lady, whom he locks in the cellar. Secretly, Gundis sneaks to the dungeon and wants to help the lady - named Klara Mälzer - escape. However, Klara does not want to flee, as she is to marry an old and miserly Spanish wine merchant whom she has never seen. Thus, Gundis allies herself with Klara.