Rebecca and Big Jim consider extreme measures as the conditions worsen in Chester's Mill; clues about Melanie's connection to the dome are revealed.

Big Jim finally learns what happened to his wife, Pauline; Chester's Mill faces a new threat -- climate change.

The residents of Chester’s Mill try to move on with their lives in the aftermath of their mysterious experience in the tunnels beneath town. Meanwhile, Big Jim suspects new residents Christine and Eva are keeping secrets concerning the Dome.

The Resistance, the citizens not under Christine’s control, join forces with an unexpected ally: Hektor Martin, the nefarious head of Aktaion. Despite Hektor revealing more about the Dome’s origins and helping to strike back at it, Big Jim and Julia still worry he will betray them. Meanwhile, Hunter receives encrypted files that give disturbing insights into the final effect the Dome will have on the infected townspeople.