Berlin, 1929. Inspector Rath was a successful officer in the Cologne homicide division before a shootout, during which he accidentally killed a man, changed his career. He was transferred to the vice squad in Berlin, a job he despises, although he finds a new friend in his chief, Chief Inspector Wolter. The city is bubbling with unrest, and the police president has tasked the vice squad with ruthlessly enforcing the ban on May Day celebrations. The result is catastrophic, with many dead and injured, and a state of emergency is declared in the communist strongholds of the city.