Wilford visits Alex in the brig.
Layton and Ruth continue to work in The Swamp and plan their escape. When the guard comes to collect their tray, they snare his arm and shiv him through the door. They steal his keys and escape to find Javi.
They come across Alex in the brig and she tells them a secret way into Wilford's quarters. They let her know that Melanie's alive.
Wilford wants Zarah to join his side. He hits Kevin for suggesting he slap some sense into her. Wilford sends Audrey to talk to Zarah.
Ruth and Layton sneak into Wilford's quarters and arm themselves. They kill the two jackboots guarding Javi.
Ruth finds the tub.
Josie gets lessons on how to move her prosthetic hand.
Alex makes her apology to Wilford. She tells Till the plan.
Javi contacts Ben with a coded message. Layton and Ruth leave him to hold the engine.
Layton and Ruth are smuggled onto Snowpiercer in carnival trunks. Boki and the Tailies receive them.
Audrey talks to Zarah, trying to convince her to side with Wilford. Till knocks at the door and punches out Audrey.
Ben attacks a jackboot as a distraction. He and Sykes fight. Ben gets beaten down but the train makes the switch onto the Rocky Mountain Test Track. He manages to tie up Sykes. Layton and Boki are in the cold lock. Boki will get Melanie when they reach the station.
Wilford notices the roughness of the track. Alex mimes a conversation with the engine but LJ calls her bluff.
Wilford sends jackboots to both engines and takes Alex with his group to Big Alice's engine. Alex secretes a razor blade in her mouth.
Javi starts to panic as they force entry into the engine. Wilford calls for his dog.
Layton spots Melanie. Boki prepares to go out to get her.
The jackboots make it through to Javi. They beat him to the floor and Wilford orders Jupiter to attack.
Wilford takes control and speeds up the train. The train races past Melanie, Wilford fully intending on pushing Snowpiercer over the cliff. Alex runs to the back window to see Melanie.
Alex asks Wilford to turn the train around. He refuses and offers to leave her trackside. She provokes him into hitting her and she slashes his neck with the razor blade and runs.
The jackboots get him to the Headwoods who patch him up. Alex hides in the subtrain and then finds Layton and Boki. She has a plan.
They decide to steal the Snowpiercer engine and ten cars, breaking the J-links at the aquarium car.
WIlford orders Josie to break into Snowpiercer's engine from the outside.
Zarah refuses to go with the pirate train. They take Audrey as a hostage.
As Josie exits to move uptrain on the outside, Sykes tells Ben about her. Ben makes contact and shares the plan.
Layton stops Wilford as he moves uptrain with his jackboots.
Ruth gets trapped by Kevin in Hospitality. She knees him in the groin and then tazes him to take back her teals.
In a showdown in the aquarium car, Layton shows that they have Audrey. Till let him know that Ruth didn't make it. Wilford figures out the J-link plan. His jackboots attack Boki in the subtrain.
Layton threatens to kill Audrey but Wilford calls his bluff. Just then, Josie breaches the aquarium from the outside. The car shatters. Ruth is left behind.
Layton and Alex trudge to the station. They find the power's been routed to keep the data drives warm but Melanie's gone.
Back on the pirate train, Alex reads Melanie's last journal logs. Ben plugs in the data and they see the areas of the earth that are warming. They prepare to chase down and retake the rest of the train.