When a former deputy goes rogue, Big Jim recruits Barbie to join the manhunt to keep the town safe. Meanwhile, Junior is determined to escape the Dome by going underground.

Junior stands up to his father and is shattered when he discovers the truth about his mother's past. Meanwhile, Julia learns firsthand the powers of the "mini dome."

While the manhunt for Barbie continues, Big Jim gets the residents of Chester’s Mill riled up and the town demands justice for all of Barbie’s supposed crimes. Meanwhile, Joe and Norrie must find a new hiding place for the mini dome.

Big Jim conducts a census to see how long the town can survive on dwindling resources; acid rain threatens everyone.

Barbie is apprehended by mysterious men and relentlessly interrogated about the Dome; Big Jim forms a deal that could permanently seal the fate of the Chester's Mill residents.

Rebecca and Sam try to save Chester's Mill residents as temperatures plunge; Barbie puts his life at risk to help Julia after a terrible accident.

A year after the dome disappears, Barbie, Joe, and the other townspeople gather for a memorial. A year earlier, Julia and Junior try to rescue Barbie and the others, but run afoul of Big Jim.

Members of The Resistance race to release their loved ones from Christine’s influence before she reaches her end game for the Dome. While Barbie risks everything in an attempt to free Eva from the Kinship, Big Jim and Julia are enlisted by Hektor, the head of Aktaion, to test a possible cure for infected townspeople. Also, Joe chooses to work with Christine after she shares some shocking information about the entity behind the Dome.