Six months later, Harry sinks deeper into depression, Grizz and Sam bond, Gordie arrives at a theory about West Ham, and Elle puts a plan into action.

A Thanksgiving feast takes a frightening turn. In the aftermath, the Guard oversteps its powers. Meanwhile, Sam is torn between Becca and Grizz.

Will tells Allie he has feelings for her. Elle confides in Helena. Campbell pressures Harry to run for mayor. Grizz leads an expedition.

Campbell plots a coup with Lexie and the Guard. Kelly spots something suspicious in a photo. Becca goes into labor. The expedition returns with news.

After the boys ransack the stores, Cassandra rallies the girls to exert their power. The students plan a prom, and Kelly uncovers a family secret.

A shocking event puts everyone on edge. As chaos sets in, Allie’s friends urge her to step up and lead. Gordie conducts an investigation.

After their class trip is cut short, students at West Ham High School return home to discover their town completely empty.

Cassandra and her friends prepare for an uncertain future, while Harry’s crew just wants to party. Sam and Becca make a discovery.

When a wealthy man hires Magnum and Higgins to find his missing wife, they are stunned when a tragedy occurs as a result of their investigation. Also, Kumu’s suspicion of…

Magnum and Higgins work a stalking case involving a man with a past in espionage. Also, Ethan asks Higgins to join him on an extended trip for Doctors Without Borders…

Dylan and Ethan treat a patient shot during a drug raid. Charles and Vanessa work together to properly diagnose a motivational speaker. Will and Hannah must turn to Crockett for…

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.

Big Jim finally learns what happened to his wife, Pauline; Chester’s Mill faces a new threat — climate change.

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.

Just as the walls start to close in on those trapped in Chester’s Mill, a possible exit from the dome is revealed.

After Big Jim and Rebecca’s plan left the town divided, Julia takes over as the leader of Chester’s Mill; Norrie and Joe help Melanie find more clues.

A cave-in severs Barbie and Sam’s path back to Chester’s Mill during their investigation of a mysterious tunnel; a dust storm rages through the town, as Big Jim and Julia…

Barbie’s life is in Big Jim’s hands; the dome becomes magnetized; Julia tries to save the life of a mysterious girl who may have clues about the origin of the…

When Rebecca discovers an infestation of butterfly eggs on the crops, Barbie risks his life to help her save the town’s food supply.

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.

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…

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…

The residents of Chester’s Mill try to move on with their lives in the aftermath of their mysterious experience in the tunnels beneath town. Meanwhile, Big Jim suspects new residents…

Coop is still trapped as Dougie, going through the motions, as his doppelganger schemes in jail. Meanwhile, new information on Major Garland Briggs turns up.