They step out into a world colder than any human has ever known. They walk towards the light. They find not a city, but a small, geothermally heated research station, powered by a different kind of engine—a deep-earth thermal borehole. Inside are a dozen scientists, descendants of a failed Arctic outpost, who never knew the train existed.

The Earth is not dead. The ice is melting, slowly, from the inside out. The train’s journey is over. A new one begins.

Seven years later, the train is a rigid, brutal class system on rails.