As Curtis reaches the Engine room, the narrative unravels several twists:
- The Insect Protein Bar Secret: Early in the assault, the rebels discover that the gelatinous protein bars are made from billions of crushed cockroaches.
- Curtis’s Dark Past: Curtis confides that during the first year on the train, the Tail passengers starved to the point of cannibalism. Curtis himself killed mothers to devour their babies. Gilliam sacrificed his own leg to feed the group, inspiring others to stop eating each other.
- The Gilliam-Wilford Alliance: Wilford reveals that he and Gilliam were close friends who orchestrated periodic rebellions. Rebellions served as controlled population culls to keep the train's ecosystem balanced.
- Child Exploitation inside the Engine: The automated parts of the perpetual motion engine have broken down over time. Wilford uses small children stolen from the Tail section to manually clean and operate tiny machinery under the floorboards.
- The Destruction of the Train: Realizing the train cannot exist without human exploitation, Curtis sacrifices his arm to rescue young Timmy from the gears. Namgoong uses Kronole as C4 to detonate the exterior door. The explosion triggers a massive avalanche, derailing the train and killing most passengers. Yona and Timmy survive, step into the snow, and spot a polar bear—confirming Earth is becoming habitable again.