Set more than seven years after the world has become a frozen wasteland, the remnants of humanity inhabit a perpetually moving train while dealing with class warfare, social injustice and the politics of survival.
Nima heads for Snowpiercer; Layton and the Tailies fight their way uptrain when Ruth is captured; Nima tries to cut a deal and runs to the rocket control room to initiate the launch sequence.
Alex sabotages the track switch computer and, with Layton's help, escapes to town hall; Till gets the drop on Ace and uses his sniper rifle to save Layton and Alex from Rat; Melanie reveals the identity of Alex's biological father.
Big Alice pulls into New Eden; Layton, Josie, and Liana sit stranded in the middle of nowhere, freezing to death, when a masked soldier appears; Alex finds herself in danger.
Layton learns who was responsible for the experiments on Josie and Liana, before also finding out who froze the world; Big Alice approaches New Eden but can't cross the booby-trapped bridge.
Nima needs more samples for his experiments, so Milius sends Wilford and the soldiers to collect; privately, Milius tells Wolf to kill Wilford; Layton wakes up on an abandoned floor and is approached by humans with toxic gas scars.
Layton hears the deal: Liana for Big Alice; he agrees and the trains dock at the silo; while Layton, Ben, Till, Ruth, and Alex stew in a holding room, Josie is taken to Headwood; Milius introduces his partner in crime: Wilford.
Big Alice catches up to Snowpiercer; Milius radios them, inviting Layton over; sensing a trap, Layton and Josie sneak onto Snowpiercer; Nima is worried Layton will be gassed and attempts to disarm the Greenhouse Car.
Layton demands to use Big Alice to rescue Liana; Ruth, now mayor of New Eden, refuses because it's the town's power supply; Layton makes Javi jury-rig a solution, giving them three weeks of electricity.
Milius and his Animal Squad storm the train; Melanie realizes something is wrong and shuts the vault doors to the engine; when Ben's life is threatened, Melanie surrenders the engine.
The Snowpiercer crew marvel as a rocket shoots through the sky, crashing nearby; Melanie sends Till and Ben to investigate; nine months later, New Eden blooms.
