Marshal Vasilevsky holds a meeting at the headquarters of the Red Army, demanding the liquidation of the Japanese chemical plant in Manchuria and to prevent the explosion of dangerous weapons depots. An echelon of soldiers arrives at the Far Eastern station, including a reconnaissance platoon, which will have to find the plant. The platoon includes Sergeant San Lee, nicknamed Sanya, and his colleague Kuzmin, a former student at the Institute of Oriental Languages. To get information about the location of the plant, the scouts need to get to Harbin and establish contact with the Soviet agent Rybak.