The film tells about the childhood and youth of the wife, friend and military ally of the founder of the country of the Soviets Nadezhda Konstantinovna Krupskaya. The main attention in the film is paid to the participation of a young revolutionary in the organization of the struggle of the workers of St. Petersburg for their rights, against the autocracy.

The young officer Sergei Lukonin faced severe trials: the war in Spain, an injury, escape from captivity, and the battles at Khalkhin Gol. Yet, he overcomes all hardships, showing courage and conviction in the justice of the cause he is fighting for.