Some sort of leaking acid is causing a mechanical malfunction in the train's systems while Third is organizing to strike.
Javi and Bennett argue over Bennett's relationship with Cavill. Bennett heads down to investigate the electrical short.
Jinju tries to guide Cavill through meditation. Cavill is distracted by the strike, then asks Jinju about Till and Jinju reveals Till never came home.
Till finds Osweiller at the Brakemen station and tells him she was looking for him, worried. He defers that conversation to later and tells her they have to track down the organizers of the strike.
Layton wakes up and Zarah catches him up, tries to get him to tell her what happened. They fight about their past and their relationship.
Cavill and a team of jackboots enter the Chains where the strike is being organized. Cavill warns them that if they strike, ten random Thirdies will be sent to the Tail and ten Tailies will be brought forward to take their place.
Josie comes to get Layton and takes him to Dr. Pelton who treats him. On the way, Layton fills Josie in on the myth of Mr. Wilford and Cavill's charade. Layton demands to know what Pelton knows about the Drawers. She tells them about the twelve cars of Drawers as well as the List of passengers marked to be Drawered.
Osweiller tells Till that he wants her to follow his lead. He uses brute tactics to question Walter the Paper-Maker, making Till comply.
Suzanne dies. Lights tells Aus she wants to do something for the Tail to lift spirits. She wants to give them a look at the outside.
Breachman Boscovic is in the classroom telling the students about his work. Cavill comes to fetch him for the repair. She stops to talk to Miles who shows her that he has completed the Physics exercise she gave him.
Zarah talks to Audrey about her fears about the strike. She reveals that she's pregnant.
Layton steals Josie chip and takes off to kill Cavill.
Cavill suits up for the repairs and updates Ruth who is still upset about the trial. Boscovic and Bennett work with other breachmen to remove the faulty motor.
Layton grabs Cavill and confronts her about the truth of the Drawers.
A chain snaps on the motor and one breachman goes flying. The motor drops down and the train rocks from the impact. The train goes into lockdown.
Cavill says the Drawers are Snowpiercer's lifeboat for humanity and then begs Layton to let her go to fix the train.
The repair team realizes that someone needs to physically climb under the train to reconnect the sensor. Cavill takes on the task.
Till and Osweiller are locked down in the prisoner holding car and Till gains some clarity and tells Osweiller that she's done following his lead.
In the Tail, Lights sets up a projector to show the Tailies what it looks like outside.
Ruth makes a reassuring announcement to the train.
Layton makes it back to Josie and Dr. Pelton.
Cavill succeeds and the train stabilizes.
Till joins Jinju and admits to doing something terrible but doesn't give her details.
Bennett and Boskovic are celebrated in Third and the Thirdies cheer Mr. Wilford. Cavill observes to Audrey that it seems the strike has been averted. Audrey isn't so sure.
Dr. Pelton gives up her quarters for Layton and Josie to hide in. They have sex.
Miles comes visit Cavill and she gives him a caliper and then asks him for a favor.