"Son of Mongolia" was the title of a 1936 film. It was the first feature film, the first Mongolian feature, shot by a Soviet crew from Leningrad. It was almost a Western comedy. But then, suddenly, it disappeared. A documentary filmmaker, the director's granddaughter, travels to Ulaanbaatar to the Mongolkino film studio, which was created with the active participation of the USSR and Lenfilm. Trying to figure out where such an ideologically important film disappeared to, she meets with the descendants of the first film actors and searches for historical clues on the roads of Mongolia, where her grandfather's film was shot.