When the body of a postman is found on Lake Neusiedl, the investigation shows that it is probably a robbery, and several of the villagers fall into the circle of suspects: Five young men now need an alibi. Walter was with Elisabeth on the night of the murder, but cannot rely on her support. She is not only the sister of Stephan, who is also suspected, but also the fiancée of the gendarme who is leading the investigation into the case.