Based on the novel of the same name by Leonid Leonov. 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 Gratsiansky. Now, when Vikhrov is already not young and lonely, the professor mentally returns to the past...