Centuries if not millennia later, the planet is entirely covered in a thick, opaque cloud layer. Giant wolf packs roam the frozen wastes, and the mammoth has re-emerged from the elephant stock. Mankind ekes out a living in a few handfuls of settlements, connected by a network of massive armored trains. The network in turn is in the hands of the gargantuan Viking Union, which is merciless towards threats to its power. A few radicals, though, are willing to attempt a change, and managing to hijack a train of the Union, the "Transarctica", they set out in search of the "sun".