Season 4

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 saves Layton and Alex from Rat. Melanie reveals the identity of Alex's biological father.

The bridge is safe to cross and 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.

Layton learns who was responsible for the experiments on Josie and Liana, and finds 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. Layton wakes up on an abandoned floor and is approached by humans with toxic gas scars.

Layton hears the deal: Liana for Big Alice. While Layton and the others 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.

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.

Melanie realizes something is wrong as Milius and his Animal Squad storm the train. When Ben's life is threatened, she is forced to surrender the engine.

When a rocket crashes nearby, Melanie sends Till and Ben to investigate. Nine months later, New Eden faces uncertain times and unknown adversaries.