Up until now, the Metro series (Metro 2033, Metro: Last Light) has been about limitation. After nuclear holocaust left the surface of the Earth an irradiated wasteland, civilization went underground. The Metro, the public transportation system built beneath Moscow, became the new limits of civilization. Occasionally, well trained warriors known as Rangers, have to pull on their gas-masks and travel above ground - but the mission has to be worth the risk. Radiation made Earth's surface a home for mutant beasts that had adapted to the toxic air. The close confines of the Metro bars against the unknown.