Karin is in love and believes she has found the man of her life. But she is worried when her new boyfriend, the doctor Harry Brenndorfer, sets off for a week to relax at the Schloss Mühldorf horse farm. There is only one thing she can do: her mother Hella also has to stay at the horse farm to keep an eye on the passionate rider. As soon as she arrives, she sees Harry and the attractive Sabine getting ready for a ride. As she cannot ride herself, the resolute lady follows the two in a one-horse carriage. During the fast-paced chase, the carriage overturns and Hella is left lying unconscious. Kurt Schleyer finds the injured woman and takes care of her. When Kurt brings her back to the horse farm, everything is in a state of excitement: Marga Lex's horse came back from the ride alone, and the rider herself was found dead in the forest. Hella finds evidence of outside influence and begins to investigate discreetly.