A grisly murder stokes class division on Snowpiercer, the Great Ark Train. Melanie Cavill, the powerful head of hospitality, deputizes a dangerous rebel to help solve the killing -- Andre Layton, the world's only surviving homicide detective.

Layton descends into the black market with Till, searching for both the killer and a valuable commodity for his revolution. Melanie stages a prize fight to distract the passengers from mounting class tension.

Tensions between Third Class and First Class are boiling as Melanie stages the trial of the Snowpiercer killer. Third Class threatens a work stoppage, demanding representation on the jury, and Melanie makes a fateful decision about which side to favor.

Hiding out with help from his allies, Layton lays track for revolution and an engineering emergency threatens every soul on Snowpiercer.

On a divided Snowpiercer, Melanie intensifies her search for Layton while Layton is weaponizing her secret. Third Class faces a reckoning when he presents them with a choice.

The rebel forces are on their heels when a dangerous foe joins them. A plan is hatched to take the train, but it may destroy them all.

In the revolution's aftermath, Layton and Melanie realize the greatest threat to their survival is right over their shoulder.

Melanie embarks on her most dangerous mission yet, while Layton reckons with his personal choices.

As the Big Alice crew are granted shore leave on Snowpiercer, Layton and Wilford have differing opinions on the future.

Layton and Miss Audrey make a risky play for Big Alice, but Wilford has his own plans.

While Wilford emphasizes his rule aboard his icy train, Layton's pirate train continues its dangerous quest for warm spots, and comes across something entirely unexpected.

Layton goes on the hunt, as Wilford works to boost morale. The resistance discovers a threat that could undermine everything they've worked for.

A series of terrorist attacks threatens to derail Layton and Zarah's big day.

Layton realises some dreams are out of reach. As the rest of the train deals with Layton’s status change, Wilford makes a staggering discovery.

It all comes to a head as old adversaries clash, with New Eden hanging in the balance.