Mr. Wilford arrives and threatens Snowpiercer, so Melanie makes a move that can't be undone.

An exchange is made between the two trains, but a far greater revelation might be just over the horizon.

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.

Melanie fights for survival in treacherous conditions, vying to do what others before her could not.

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.

Wilford presses forward on his endgame while those who are close with Layton grow anxious to learn their fates; Josie tests her newfound ability.

As the train approaches Melanie's retrieval point, Layton leads a furious attempt to try and pick her up but not without some sacrifices.