Young Polya comes to Moscow: she wants to find her father, Professor Vikhrov, and try to understand why her mother broke up with him. Vikhrov is a prominent scientist who has defended the forest from barbaric destruction all his life. The war begins. Professor Vikhrov continues to lecture, proving to students the need to protect the forest. Polya is trying to find out the reasons for the long-standing feud between her father and academician Gratsianskiy. Now, when Vikhrov is already not young and lonely, the professor mentally returns to the past.

Andrei Latonin had jumped with a parachute many times before, but on the day of the holiday he got scared and stayed in the cockpit of the plane. Deeply upset by his failure, Latonin decides to leave his homeland forever and joins a steamship as a sailor. On the way, Andrei meets an expedition group heading for the crater of an active volcano and joins the scientists.

After graduation, Nadia Kulagina comes to work in a school where she once studied. After her appearance, the most hopeless student Dimka Lopatin, who was even wanted to be expelled from school, becomes one of the best students and a faithful friend of the new class teacher.