When Big Jim and Julia team up to find proof to discredit Christine, they learn something new about the dome. Meanwhile, when Christine's leadership is threatened, she puts a plan into motion with deadly consequences.
After being captured by Aktaion, Big Jim is forced to manipulate Christine for information about her agenda. Meanwhile, when Joe and Norrie question the town's new rules, they find themselves in a dangerous face-off with the increasingly unstable residents.
Barbie risks everything in an attempt to free Eva from The Kinship, Big Jim and Julia are enlisted by Hektor to test a possible cure for infected townspeople. Joe chooses to work with Christine after she shares some shocking information about the Dome.
As the dome's calcification accelerates, the townspeople have 24 hours left before they will suffocate; Julia and Barbie race to save Barbie's child; Hektor is adamant that the infected townspeople should never escape from the dome.