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.

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.

When the town begins to run low on water, the residents of Chester's Mill begin to fight for the remaining resources. Meanwhile, Julia discovers a strange connection that two of the town's residents have with 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."