Schoolboy Petya Ivanov receives a letter from a famous scientist and 20 grains of a new high-yield variety of wheat. Petya and his schoolmates decide to create an experimental plot. Fearing that adults will take the seeds away from them, the children do everything in secret.
The film is set in old Yuzovka on the eve of 1905. After searching the Kolchugins' apartment, where money from the strike fund was hidden, the police arrest Anna Kolchugina and her lodger, the miner and revolutionary Kuzma. Anna's teenage son, Stepan, is forced to go to work in the mine. There he learns about the existence of the revolutionary underground and joins its struggle.
