As conditions in Chester's Mill worsen, Big Jim and Rebecca consider resorting to the extreme measure of population control, which drives a wedge between Barbie and Julia. Meanwhile, clues to Melanie's past and her connection to the Dome are revealed.

When Barbie and Sam set out to investigate a mysterious tunnel, a cave-in severs their path back to Chester's Mill. Meanwhile, Julia and Big Jim face off in a struggle for power as a dust storm rages in the town.