Twelve-year-old Sanya Linev lives on a farm. He invents a flying machine. However, no one believes in his idea... To find out what fuel is needed for the device, Sanya sends a telegram to Academician Alexandrov. He shares his dream with a girl he knows, Sasha, but then he has to endure the bitterness of betrayal - the girl brings teenage hooligans to Sasha’s device, and they smash it... He’ll have to start all over again, but faith in the dream is supported in Sana by a response letter from Academician Alexandrov