In a dark future, the remains of civilization can only survive in mysterious, bunker-type skyscrapers. The cellar floors are inhabited by a working class, who have never seen the light of day. In solitude they lead a brutal existence, only as working machines. When one day, a discarded music box lands on the factory floor and is causing a rebellious dance, two workers are forced to run for their lives. Heading to the top of the building, they discover a world unknown and have to decide if they are ready to take a leap into the abyss.