Julia takes over as leader of Chester's Mill after the town becomes divided in the wake of Big Jim and Rebecca's plans for population control. Meanwhile, Joe and Norrie continue to help Melanie search for more clues about her identity.
As temperatures continue to plunge, Sam and Rebecca spring into action to try and save the residents of Chester's Mill. Meanwhile, Joe remains suspicious of Hunter, and Barbie and Julia face danger after black ice causes their vehicle to crash.
When a new threat from the Dome intensifies, the residents of Chester's Mill find themselves at risk of being crushed to death. Meanwhile, Melanie's health continues to deteriorate as the fate of the egg remains unknown.