Police commissioner Gereon Rath is transferred from Cologne to Berlin, the epicenter of political and social change in the Golden Twenties. Shellshocked from his service during World War I, he uncovers a dangerous web of intrigue while investigating one of Berlin's biggest pornography rings. There's an even bigger conspiracy unfolding, though, when Soviet rebels hijack a train as part of a mission hatched by Trotsky supporters in the city.