Sudba barabanshchika

In the life of Sergei Batashov, a young drummer of a pioneer organization, trouble comes. His father, an engineer at a secret factory, is arrested for losing documents. Guilty of this his stepmother marries and leaves Sergei alone. Using the trustfulness of the boy left to himself in the Batashovs' apartment, a criminal espionage organization was established. Introducing themselves as distant relatives of the boy, they use it for their own purposes, forcing them to acquaint them with his father's colleagues. A young boy, a drummer for a pioneer organization, discovers that his stepmother is cheating on his father, but does not tell him so as not to harm him. Believing that an envelope may contain information that will reveal his secret, the stepmother steals the from her husband's wallet, a military engineer. The envelope is accidentally lost. With the father imprisoned for the loss of important military secrets, the stepmother leaves the boy alone in order to have an adventure in another city with her lover. The innocent boy ends up falling into the hands of a criminal organization that wants to take over the project of the engineer with whom his father worked. One of them pretends to be the stepmother's brother and drags the boy along. He makes him believe that he actually is trying to save him from being arrested for having sold his stepmother's clothes to survive. The false uncle uses him to get close to the engineer, who also has a child, and to get hold of the project.