After Snowpiercer is confronted by Mr. Wilford's people, the survivors regroup to draw a defensive line – while Melanie is forced to board the second train and face Mr. Wilford himself.

After Mr. Wilford arranges for a prisoner exchange with Snowpiercer, Melanie pursues a recent discovery. As the various elements on the train seek new alliances, Hospitality prepares to welcome Mr. Wilford on board.

Melanie prepares to depart the train for a research station in the Rocky Mountains, and seeks to connect with Alex before she leaves. Till investigates the assault on Lights, and Layton reconnects with Josie.

Mr. Wilford arranges for he and some of his crew to enjoy a night out on board Snowpiercer, where he seeks out Audrey – his former escort who has tried to put their relationship behind her. Josie receives an offer she can't refuse.

As Audrey receives an invitation to dine aboard Big Alice, a smuggled message prompts Layton and his people to prepare for Mr. Wilford's next move. Pike is attacked by Terence's people, and Josie puts herself on the line to gain intel.

Melanie's arrival at the Breslauer Research Station is only the beginning of her fight for survival, as she is plagued by hallucinations – and memories of her past actions before the freeze.

As Till investigates the gruesome murder of eight Breachmen, Wilford's loyal followers decide to hunt for Tallies in retribution. Audrey goes down a dark path when she is forced to prove her loyalty.

Wilford precipitates an engineering crisis on Snowpiercer, forcing Layton to turn to Breachman Boki in the middle of rising tensions between Wilford's followers and everyone else.

Snowpiercer's crew are unsettled by Mr. Wilford's efforts to impose his own form of order, including a census of every passenger and a disturbing new attraction. Josie confronts the Headwoods, while Layton is forced to toil in the engine compost.

Layton and Ruth make their escape from Big Alice with a plan to rally their allies and retake the train in time to rescue Melanie. But Wilford and his supporters won't go down without a fight.