A family is having a great time at the amusement park, but when the parents return to the hotel room after dinner, their eight-year-old daughter is missing. A little later, the girl is found dead in a torrent on the site. Lena Odenthal and Mario Kopper quickly track down two suspects: Tom Heye, a carpenter who was convicted of abusing a girl, and lawyer Werner Rahn, who died last night before his weddingspent alone in the amusement park. But then the case takes a surprising turn and the mother herself becomes the focus of the investigation. An extreme situation that puts more and more strain on Lena, because she knows that she must hurt the mother endlessly with her questions - but she doesn't know whether she is sitting opposite an innocent mother who has just lost her only child, or a murderess who killed her own child.