February 1941, wartime Berlin. Brilliant, idealistic young detective Georg Heuser joins the Murder Squad in the midst of the biggest manhunt the city has ever seen. A serial killer is slaughtering women on S-Bahn trains and leaving their battered bodies by the tracks. Heuser must confront evil eye-to-eye as he helps track down the murderer. July 1959, peacetime West Germany: a pioneering young lawyer, Paula Siebert, is in a federal unit investigating men who have committed crimes of unimaginable magnitude and horror. Their leader has just been arrested. His name is Georg Heuser. Siebert is sure of his guilt. But how could a once decent man have become a sadistic monster?