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

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.

As Barbie descends further into the mysterious tunnel in hope of finding Sam, he comes across a world filled with unanswered questions.

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.

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.

The latest threat intensifies, leaving Chester's Mill residents at risk of being crushed to death; Melanie's health declines as the egg's fate remains uncertain.