On a November morning, the body of young Russian Sonja Achmatova is found in a water ditch on a riding stable on the outskirts of Bremen. A suspect is quickly identified: a stablehand who had an affair with the victim - a routine case for Chief Detective Heiner Hölzle. However, during the investigation, Hölzle and his colleagues initially discover parallels to two unsolved murder cases from the 1970s and eventually uncover a lead that dates back to 1943.