Alyosha Ptitsyn, a third-grader decides that he wants to improve his personality and immediately starts to act.

Sasha Rumyantsev, a long-range driver, becomes an unwitting accomplice in a crime committed by the head of the motor depot where he works. The honest guy is accused of stealing a car of a hard-to-find product. The collective of the motor depot amicably stands up to protect their comrade and helps the investigator, Colonel Afanasyev, to find and expose the true criminals.

Maxim Perepelitsa is a cheerful, mischievous and resourceful young man from a Ukrainian village. He loves to make up stories and invent practical jokes. When he is drafted into the Russian Army, he doesn't stop his antics.

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.