As Barbie's fate lies in Big Jim's hands, the dome presents a new threat when it becomes magnetized. Meanwhile, Julia seeks out the help of a stranger to save the life of a mysterious girl.

As the news of Angie's murder spreads, Rebecca warns Big Jim of a caterpillar infestation that could infect the town's remaining crops.

As resources dwindle, Big Jim holds a census in order to forecast how long Chester's Mill can continue to exist under the dome, while chaos ensues when a rainstorm turns into acid rain.

While Julia and Sam attempt to stop Big Jim and Rebecca's plans for population control, Barbie, Joe and Norrie try to jog Melanie's memory, and Junior turns to Lyle for answers.

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 iden...

When Barbie and Sam investigate the mysterious tunnel beneath the high school, a cave-in severs their path back to Chester's Mill. Meanwhile, Big Jim deals with a dust storm.

After finding themselves outside the dome, Barbie turns to his estranged father for help, and Sam reunites with Pauline.

Barbie realizes Don knows more about the dome than he is letting on when he asks him to help get a message to Julia. Back in Chester's Mill, Big Jim appoints himself sheriff of the town.

Barbie, Sam, Pauline, Lyle and Hunter try to evade Don and his forces and find a way back to Chester's Mill, while Junior and Melanie hide the egg from Julia and Big Jim.

The residents of Chester's Mill continue to argue over what to do with the egg to ensure everyone's safety, while Junior is haunted by a familiar face.

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 veh...

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.

A potential exit from the Dome is revealed just as the walls begin closing in on those trapped in Chester's Mill.