A peaceful day in the small Maine town of Chester's Mimll turns into a nightmare when an invisible, impenetrable dome slams down around the town, trapping the townspeople and several passing strangers inside.

Panic is heightened when a house catches on fire in Chester's Mill, but the fire department is outside of the dome.

After a former deputy goes rogue, Big Jim asks Barbie to help keep the town safe; Junior determines to escape the dome by going underground.

The people of Chester's Mill fall into a state of panic as an outbreak of meningitis strikes their community, threatening their already depleted medical supplies. Meanwhile, Julia continues to search for answers into her husband's disappearance.

The government busses visitors in to communicate with their loved ones trapped within the Dome. Meanwhile, Barbie learns from a soldier that the Army plans to drop a bomb on the Dome when it threatens the outside world.

As the town's water supply dwindles, people start to fight for the remaining resources; Julia uncovers a strange connection that two Chester's Mill residents have with the dome.

Feeling threatened that he is losing his authority, Big Jim takes matters into his own hands. Meanwhile, the dome asserts its actions after a newborn's birth.

Barbie, Linda, and Big Jim try to take back control of the town's main water supply from Ollie.

After she has a seizure, Junior shows Angie a painting his mother made that sheds some light on the secrets of the Dome. While Joe and Norrie try to find the missing mini-dome, Big Jim receives a visitor from a past and organizes a voluntary program to collect balloons from the townspeople.

Maxine continues to tighten her grip on Chester's Mill with Barbie's unwilling help, so he decides to tell Julia the truth about her husband's passing. Meanwhile, Big Jim finds out why Maxine is so interested in Chester's Mill, and Joe, Norrie, and Angie find the fourth hand.

There's no fury like a woman scorned when Maxine takes revenge for Barbie rejecting her. Meanwhile, Angie, Joe, Junior, and Norrie grow closer to learning the secret of the Dome. However, when one of them leaves the circle, the Dome makes its displeasure clear.

While Big Jim and Linda lead the townspeople in the search against Barbie, accused of multiple homicides, Dodee remembers her encounter with the Egg and learns about the army's interest in Barbie. However, she makes the mistake of telling Big Jim what she knows.

Secrets of the Dome are revealed and Big Jim is determined to put an end to Barbie once and for all. Meanwhile, Junior, Angie, Joe and Norrie discover who the Monarch is after receiving a shocking visit from a familiar face.