The hard days of August 1941. Enemy troops approached Zaporozhye, the island of Khortitsa was captured, and the Nazis shelled the city from its high banks. Our troops sought to recapture this bridgehead at all costs. Schoolchildren - fighters of the "Young Chapaevets" detachment - helped the Soviet soldiers.

A Soviet scientist creates a brilliant robot. This is a boy who is able to solve any mathematical problems, he writes the best essays and sings perfectly! And he is also an exact copy of schoolboy Seryozha Syroezhkin. A clever boy quickly shifts all his duties to an electronic double. He does his homework for him, goes to school and does household chores that his parents entrust to Syroezhkin...

Professor Gromov constructs a robot called Electronic, which looks exactly like Sergey Syroezhkibn, a 6-grader from one of Odessa (USSR) schools. The robot also acts a lot like a human, and its dream is to become a real man. Electronic escapes from the professor's lab and accidentally meets Sergey, his prototype. Meanwhile, a gang lead by Stump is trying to kidnap Electronic to make him steal pictures from museums. For this purpose they send their hitman Urrie.