In the town of Zatonsk, on the banks of the Volga, the schoolteacher Arseniy Gay and his students Kapiton, Valera and Timson have imagined a tale about the magical land of Sinegoria, where reckless people live. The war begins. Gay was one of the first to reach the front and was killed defending Leningrad. His students, left alone, organize the Sinegoriev detachment, help the families of soldiers who have gone to the front, work in a factory manufacturing military equipment to apply in real life the motto imagined for their tale: "Courage, loyalty, work, victory". After the funeral, the children name a star after their teacher. Then they go in search of the place where he was killed.
