Cases of infected animals appear near one of villages in Sumava region. Virologist Pavel Rogl, that is in his thirties, has task to inspect the situation, supervise the vaccination and find the source of infection. He is also charged to elaborate an expertise for team of police detectives, who are investigating mysterious double homicide, that happened in nearby forests. It is possible, that murders are connected to infection. Young scientists get in touch with his former classmate Gabriela and her sister Tana. As their father is suspected from commitment of brutal murders, they start their own investigation. The more they discover, the more they attract attention of murderer, that neither wants to be revealed, nor arrested. Body count grows and burdensome secret from post war history of village is being slowly revealed.