Berlin, April 1929: Cologne police lieutenant Gereon Rath (Volker Bruch) joins his colleague Bruno Wolter (Peter Kurth) in the investigation against a porn ring in Berlin. After a raid his case turns into a new direction after stumbling over a photograph. He meets the stenographer Charlotte Ritter (Liv Lisa Fries) who feeds her family with work for the police. In a heist on a freight train russian revolutionaries append a wagon with explosive content to be smuggled to Berlin.