The Soviet boys, Vadik and Yura, together with the mischievous little girl Tosha, are children with a kind heart and good life philosophy. One day they find money on the street, which must be returned to the owner without fail. But where to find an inattentive citizen who has lost not only money, but also a booklet with quite important information. So, begins the time of exciting adventures, breathtaking moments, high-quality humor and instructive-entertaining ideological line.

In 1920s Moscow, shortly after the October Revolution, a stray dog named Sharik is taken in by Professor Preobrazhensky, a wealthy and respected surgeon. The professor performs a daring medical experiment on the dog that changes him into a human being. As the newly transformed Sharikov begins to navigate life in the professor’s apartment, his crude behavior and revolutionary ideas turn the household upside down.

1934. After the suppression of the uprising of the Schutzbund workers, engineer Hans Müller leaves Austria and emigrates to the USSR. In Russia Hans finds his love. His relationship with Galina is not simple. Her son Sanka agonizes over the arrival of a stranger in the house. But, in the end, Hans wins the boy's trust. When in Spain begins the Frankist rebellion, Hans voluntarily goes to fight in the ranks of the interbrigade. And after the liberation of Vienna, he returns to his homeland.