This is a story about two detectives from different social classes who are destined to investigate crimes together in the Russian capital during the post-revolutionary period. Numerous ruthless criminals and dangerous criminal groups terrorize the city's residents. Former investigator of the Tsarist police, Nikolai Varaksin, and Baltic sailor, Petr Sokolov, are tasked with dealing with this. However, the main characters, being very different, do not immediately find understanding with each other.