Following Duke's death, his house catches fire, forcing the town to rally together to form a bucket brigade. Elsewhere, Junior ambushes Barbie, while Dodee and Phil pick up a military frequency.

The Chester's Mill residents receive an unexpected visit from their loved ones on the other side. Meanwhile, the community braces for a threat from outside the Dome.

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."

Secrets of the Dome are revealed and Big Jim is determined to put an end to Barbie once and for all. Meanwhile, Junior, Angie, Joe and Norrie discover who the Monarch is after receiving a shocking visit from a familiar face.

Barbie's life is in Big Jim's hands; the dome becomes magnetized; Julia tries to save the life of a mysterious girl who may have clues about the origin of the dome.

A cave-in severs Barbie and Sam's path back to Chester's Mill during their investigation of a mysterious tunnel; a dust storm rages through the town, as Big Jim and Julia face off in a power struggle.

Barbie turns to his father for help contacting Julia but realizes that he may not be trustworthy; Big Jim declares himself sheriff of Chester's Mill.

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.

Just as the walls start to close in on those trapped in Chester's Mill, a possible exit from the dome is revealed.