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.

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.

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

Milius and his Animal Squad storm the train. Melanie realizes something is wrong and shuts the vault doors to the engine. But when Ben's life is threatened, Melanie surrenders the engine.