Imagine ... you're trapped inside the Dome. Food and water supplies are diminishing by the day. You've got an entire town to keep alive. What would you do? With the census complete, Big Jim (Dean Norris) is hesitant to put Rebecca's (Karla Crome) plan -- "thinning the herd" by ridding Chester's Mill of the weak -- into play. In his office, he questions Rebecca, wondering if the Dome really wants him to "play God." Just as he turns to leave, Rebecca steals his ID card. Julia (Rachelle Lefevre) asks for Sam's (Eddie Cahill) help -- she's afraid of what Big Jim and Rebecca have in store, and is even more concerned that Barbie (Mike Vogel) might be on their side. But over at the Sweetbriar Rose, Barbie makes it clear to Big Jim: No one makes any decisions until they both agree on a course of action.
Joe (Colin Ford), and Norrie (Mackenzie Lintz) continue to search for answers with Melanie (Grace Victoria Cox). Barbie finds the teens on Julia's porch, and Joe explains that they'd actually received email and found a possible source of the Internet connection. Across town, Junior (Alexander Koch) confronts jailed Lyle (Dwight Yoakam) about Pauline. Lyle agrees to help, but only if he's released -- and Junior begrudgingly agrees. Rebecca meets with a Chester's Mill farmer. One of his pigs has died; could it be a virus? Rebecca secretly takes a sample of the pig's blood.
The kids take Barbie to where they found the 'Net signal at the school. They ultimately show a confused Barbie the 1988 yearbook, and he agrees to help them figure out who Melanie really is. According to town records, Melanie and her family moved to Chester's Mill from Zenith -- where Barbie is from -- right before she (evidently) "disappeared" in '88. Later, an angry Big Jim finds Rebecca at the town's lab, where she used his ID to access equipment. Her aim? To create a swine flu to release into Chester's Mill -- a kind of Darwinian "survival of the fittest." Big Jim wonders ... maybe this really is the Dome's plan.
At the barbershop, Lyle shows Junior a stash of postcards that Pauline has been sending ever since her "suicide." Shockingly, they all depict things that have happened in Chester's Mill since the Dome appeared -- including Angie's death. Pauline also kept a journal; Junior wonders if it might hold a clue to Angie's killer, so they head over to Sam's to find it. Meanwhile, Barbie and the teens check out her family's old house, where Melanie suddenly remembers seeing "pink stars" from her window -- near where the "mini-Dome" recently appeared. Once in the forest, Melanie has intense flashbacks of the night she went missing. She was dating a teenage Sam in 1988 -- and she'd gone searching for the stars with him, Lyle, and Pauline. They found a "meteor," and -- the minute they touched it -- it opened to reveal a glowing egg. (Could they be the original "Four Hands"?) As Melanie tried to save the egg, someone pushed her down a ravine ... and she died. How is she now alive? And why hasn't Sam recognized her? Barbie proves her story, digging at the site and finding a large metal object -- and Melanie's old necklace!
Rebecca finally convinces Big Jim that her plan is sound -- it's a tough choice that must be made. Just as he's about to contaminate the water at the Sweetbriar Rose, he's stopped by Sam and Julia. But Rebecca actually has the vial of virus -- and just as she's about to contaminate the holy water at the church, she has a crisis of conscience. Sam and Julia bring them both to jail; Big Jim feels used, and Rebecca reveals she couldn't release the virus either -- especially not after she realized it might have a dangerous mutation. Just before he's locked up, Big Jim lies to Julia, telling her Barbie was on board with their plan from the beginning. Lyle and Junior find Pauline's journal at the cabin; ultimately, Lyle knocks Junior out and escapes. Barbie and the kids find him, and he explains that Lyle may have killed Angie. Maybe he killed Melanie too?
Barbie shows up at Julia's house, but she angrily tells him to leave. As she thanks Sam for his help, he leans in to kiss her; she pushes him away, but doesn't make him leave. As she turns to make them some tea, Sam looks at the mysterious wounds on his shoulder ...