Secret, for All the World Only (1977)

Based on the book of Viktor Dragunsky "Deniskin's Stories".
Once upon a time there lived in Moscow the 1950's an October school student Deniska Korablyov. Every day he was terribly busy with the most ordinary children's activities: he did not prepare lessons, quarreled and put up with classmates, helped around the house and dabbled. He also planned a real murder, crossed paths with the criminal Fantômas, exposed the adult liars and thieves, participated in the selfless rescue of man...