Zakhar Psaltyrev went through many ordeals in the royal fleet, where massacres and bullying of people became a custom. Only thanks to his natural intelligence and perseverance, the illiterate peasant boy managed to avoid the fate of many of his comrades, who became drunkards and lost their human dignity. Captain 1st Rank Lezvin, commander of the cruiser "Svyatoslav", himself suffocating in the difficult atmosphere of the tsarist autocracy, fatherly fell in love with his messenger for his simple Russian soul, quick-witted mind, love for the homeland and hatred of oppression. Zakhar learned a lot from Lezvin, but soon they had to part. Zakhar becomes an active underground Bolshevik.

The film is about events which has happened with the "Potyomkin" ship.

A group of young scientists conducts an experiment, putting themselves in the conditions of the people of the Stone Age. With the help of stone tools, they procure food and fire, and make themselves comfortable in nature.