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.

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.

Revolution has finally come. As Layton leads the lower classes forward in armed rebellion, Melanie's house of cards collapses.

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

An engineering catastrophe on Snowpiercer forces Layton to make a difficult choice, one that might cost him everything.