In a post-apocalyptic world where a deadly ice age has taken over the Earth, there are only a few survivors, all of whom have taken shelter in an enormous train propelled by perpetual motion. While the rich and powerful live in luxury at the front end of the locomotive, the poor have been forced to dwell at the tail with limited supplies by the dictatorial Minister Mason. During a routine deliverance of protein blocks, one tail inhabitant, Curtis, decides to round up a rebel army to invade the front, though no-one could have imagined the amount of bloodshed the ensuing revolt would trigger. In a bid to destroy the barbaric class hierarchy this new life has caused, Curtis plots a major act of disaster. It starts to look like the human race really will be the death of themselves.