Till and Ben are sent to examine the debris from a rocket detonated near the train, and are shocked to encounter a militarized group of survivors. Nine months after Big Alice separated from Snowpiercer, Layton and the residents of New Eden attempt to forge a new settlement in a hostile environment – unaware of what is approaching in the dark.
Nine months ago, Ben and Bess's investigation of the rocket debris leads to Snowpiercer being boarded by an armed squad under the command of Admiral Anton Milius. Melanie is forced to choose between control of the train and Ben's life.
Layton demands to use Big Alice to rescue his daughter, putting him at odds with Ruth and the other leaders of New Eden. Bess and Ben are forced into service on Snowpiercer.
New Eden struggles through an oncoming storm as the team on Big Alice prepares for a dangerous incursion. But Layton's plan is cut short when Milius invites him on board Snowpiercer.
Admiral Milius offers Layton an impossible choice, demanding that the crew from New Eden gives up Big Alice in exchange for Liana. But when they arrive at the silo they learn that Milius has made a new ally.
Layton finds himself a prisoner inside the silo facility, and Milius decides that Mr. Wilford has outlived his usefulness. Back at New Eden Javi finds a survivor in the wilderness.
Melanie returns to the silo, unaware of what Milius has orchestrated for the people she cares about. Layton and Alex make an unlikely alliance with Wilford to try and escape, and as Big Alice approaches New Eden the crew discover that the bridge has been boobytrapped.
Josie, Layton, and Liana are desperate for rescue outside the silo, while Nima looks for a way to recruit Alex to his cause. Big Alice arrives at New Eden, where the survivors must plan for the silo's inevitable attack.
As New Eden comes under sniper fire, Alex sabotages the track switch computer and temporarily thwarts Nima's plan. Bess and Osweiller plan to go after the sniper, and Nima presses Melanie to help him in order to spare the lives of the colony.
Layton and the former Tailies fight their way upstrain in an effort to take back Snowpiercer from the soldiers, while Melanie and Alex look for a way to sabotage Nima's plans – with the future of the planet and all of humanity at stake.
