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.

A shocking twist in the murder investigation brings Layton and Till's manhunt to a cat-and-mouse climax. But Layton is getting too close to Melanie's big secret, which may prove the most dangerous game of all.

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.

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

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

Layton and Till investigate the murders. Wilford leads Miss Audrey down a dark path.