The world that survived a nuclear war. Residents of the Soviet Union live in bomb shelters. The largest of them is under the city of Pobedograd and it goes down a hundred floors... Fifth-grader Mitka lives in an underground city all his life, travels by metro to the Palace of Pioneers, studies at school and dreams of seeing the world on the surface. But at the top, where the nuclear summer has descended on the world, radiation is impossible to live. And the subway tunnels are home to ghosts and scary creatures that drag unwary diggers into the darkness. And a mysterious ghost train walks through the tunnels... But in the depths of the bomb shelter, a new threat has appeared that can destroy all its inhabitants. Now their fate is in the hands of a brave eleven-year-old boy and his faithful friends...