After news of the future birth of a child, Sergei split from his wife, Natasha, and settled in the company of young architects, who occupied a room in a big house. As a result of a chain of unforeseen events, brought by one of the tenants found a child, Sergei finds a newborn son. Friends are doing everything possible to find a lost mother, but Sergei does not disclose their affiliation and tries to give the baby the wrong hands.

The film takes place in 1921 on the Soviet-Finnish border. Shyutskorov detachments broke into Karelia, killed Soviet activists, burned houses ... In the rear of the enemy with a special task - to destroy the headquarters of the White Finns on the Kimas Lake - a detachment of Soviet cadets under the command of Toivo Antikainen (Oleg Zhakov) was sent.