A year after the dome disappears, Barbie, Joe, and the other townspeople gather for a memorial. A year earlier, Julia and Junior try to rescue Barbie and the others, but run afoul of Big Jim.
Barbie investigates Ben's claim that something strange is going on in Chester's Mill, but Eva surprises him with unexpected news. Meanwhile, Norrie and Hunter grow closer, and Christine advises Joe to move on.
Under the guise of helping Chester’s Mill rebuild, Christine urges the townspeople towards specific individuals and projects that remind them of their experience in the tunnels. Also, Julia and Big Jim make shocking discoveries that reveal a new threat within the Dome.
Big Jim and Julia form a tentative alliance to search for proof that will discredit Christine, which leads them to new information about the Dome’s capabilities. Meanwhile, when tensions run high in town and threaten Christine’s leadership, she puts a plan in play that has deadly consequences.
When Big Jim is captured by Aktaion, the dangerous private corporation that’s descended on Chester’s Mill to harness the Dome’s energy capabilities, he’s forced to manipulate Christine for information about her agenda. Also, when Joe and Norrie question the town’s new rules, they find themselves in a dangerous face-off with the increasingly unstable residents.
As the world outside the Dome is rocked by a catastrophic meteor shower, unexpected alliances form inside the barrier. Eva tries to indoctrinate Barbie deeper into The Kinship and Big Jim and Julia turn to one another while isolated on Bird Island outside of town. Also, Joe is forced to accept help from Sam, the man who killed his sister.
Big Jim, Julia, Joe, Norrie and Hunter join together to form a resistance against Christine, who is mobilizing residents to work on a massive excavation project in the caves underneath the town. Also, Hunter uses his tech skills to contact the outside world.
Big Jim and Julia devise plans to end Christine’s control over the town by initiating a life-or-death plot involving Barbie and Eva, while Joe and Norrie conduct research to better understand the Dome’s ultimate agenda. Meanwhile, Hunter finds more information about the true head of Aktaion, the nefarious private corporation that wants to harness the Dome’s energy.
The Resistance, the citizens not under Christine’s control, join forces with an unexpected ally: Hektor Martin, the nefarious head of Aktaion. Despite Hektor revealing more about the Dome’s origins and helping to strike back at it, Big Jim and Julia still worry he will betray them. Meanwhile, Hunter receives encrypted files that give disturbing insights into the final effect the Dome will have on the infected townspeople.
Members of The Resistance race to release their loved ones from Christine’s influence before she reaches her end game for the Dome. While Barbie risks everything in an attempt to free Eva from the Kinship, Big Jim and Julia are enlisted by Hektor, the head of Aktaion, to test a possible cure for infected townspeople. Also, Joe chooses to work with Christine after she shares some shocking information about the entity behind the Dome.
When the Dome’s calcification process accelerates, Chester’s Mill has 24 hours before the barrier’s breakdown will suffocate everyone inside. While the new deadline puts added pressure on Joe to bring the Dome down, Barbie and Julia race to save his child from The Kinship. Also, Big Jim tries to manage the increasingly volatile Hektor, who is adamant that infected townspeople never escape the Dome.
Series Finale: As the Dome in Chester's Mill comes down, the Resistance makes a final attempt to protect the outside world from the infected townspeople in the Kinship and their new queen.
