The societies of the two worlds are segregated by law. While the upper world (Up Top) is rich and prosperous, the lower (Down Below) is poor. Up Above buys cheap oil from Down Below and sells electricity back to Down Below at higher prices. A person from Down Below going Up Top (or having contact with anyone from Up Top) is strictly forbidden and can be punishable by incarceration or death. People from Up Top regularly visit Down Below to experience novelties like dancing on ceilings. The only physical connection linking the two worlds is the headquarters of the "TransWorld" company.