In the middle of winter, little Sabine is found dead in an outdoor pool. Coroner Dr. Graf confirms Moser's suspicion: It was not an accident, the location is not identical to the crime scene. The child was killed in another bath. In the changing rooms, Rex finds a trace: Sabine's wallet. With his help, Moser wants to lure the perpetrator into a trap. And indeed, after a long nightly wait, a man enters the swimming pool. But he has an alibi for the time of the crime. However, another suspect confesses to the murder shortly afterwards – the case seems closed. But Moser still has doubts and continues to investigate. Then Rex finds another child on the grounds of the swimming pool – buried, but still alive. Rex is on his own...