Based on a true case: Kappe and a series of murders in Niederbarnim. January 1920: A gruesome murder has occurred at Tegeler Fliess. A couple was attacked and killed, with the woman having been raped beforehand. This is already the fourth crime of this nature in over two years, during which a serial killer has been on the loose in the northern suburbs of Berlin. This is reason enough for the district of Niederbarnim to request reinforcements: Commissioner Hermann Kappe and his colleague Galgenberg are brought in to solve the murder cases. However, the investigation is hindered by the Kapp Putsch, which puts Berlin in a state of emergency for four days. Then another double murder occurs, and time is running out.