Barbie (Mike Vogel) wakes up from a dream about Sam (Eddie Cahill). He and Julia (Rachelle Lefevre) agree that they should tell Junior (Alexander Koch) and Joe (Colin Ford) about Sam's confession that he's responsible for Angie's death, not Lyle (Dwight Yoakam). Barbie and Julia find Junior, Melanie (Grace Victoria Cox), Norrie (Mackenzie Lintz), and Joe and fill them in; naturally, Junior doesn't believe his uncle could kill someone, and storms out. Despite Julia's worries, Barbie decides to go back into the tunnels to try and find Sam's body; the scratches on Sam's shoulder are their only "proof" of his guilt. An increasingly suspicious Big Jim (Dean Norris) finds Barbie gathering climbing supplies, and Barbie weaves a white lie to throw him off. Rebecca (Karla Crome) and Julia help Barbie rappel down the side of the trench; suddenly, an unseen force pulls Barbie further into the blackness. The rope's anchor comes loose, and the women grab on. Fearing for everyone's safety, Barbie takes matters into his own hands. He cuts the rope ... and tumbles into the abyss!
At the diner, Melanie and Junior discuss Sam's confession -- just in time for Big Jim to overhear. Father and son are still at odds; once Melanie leaves, Big Jim tries to convince Junior that the Dome chose him (and by extension, his son) to save the town ... but Junior is having none of it. Back at school, Julia asks Rebecca to keep Barbie's fall a secret until she comes up with a plan. A curious Big Jim finds the pair, and asks about Barbie; Julia buys some time by asking him to answer phones at the police station. Next thing we know, we're suddenly in the middle of a playground: children playing, people walking dogs, sunshine, fresh air. Barbie comes to -- and realizes he's definitely not in Chester's Mill ...
Barbie starts wandering through town. It's familiar: the skyline, the people ... the obelisk. It's Zenith! He's made it out of the Dome and is back in his hometown! Just as Barbie sees someone erasing "@houndsofdiana" graffiti from a billboard (belonging to a company called Aktaion Energy), we see Sam walking through the very same town! He's on his way to a psychiatric hospital ... to see his sister Pauline (Sherry Stringfield). Meanwhile, Joe believes he can help Julia find out Barbie's fate by using a drone-style camera. Big Jim surprises Rebecca at her house; he's steaming mad, and realizes he never should've trusted her. Ultimately, Rebecca admits that Barbie is probably dead. In Zenith, Barbie goes back to his old apartment -- but he's got some unwelcome visitors.
Barbie's "associate" Rick is angry -- where's he been? And why hasn't he completed his latest job? Seems Barbie was supposed to get some intel on Aktaion Energy, and Rick threatens more violence if the job isn't completed today. Pauline and Sam reconnect; she explains why she faked her own death, and why she sent postcards to Lyle ... just before admitting that Lyle, too, is now in Zenith. In the tunnels, Joe's robotic camera only makes it 20 feet below before it loses its signal. However, Joe spots something strange in the footage he managed to record: he, Julia, and Norrie realize ... it looks like a playground. Could Barbie be alive? Barbie and a henchman are about to break into a mansion -- but Barbie sets off the home's alarm and attacks his cohort instead. The house belongs to the owner of Aktaion Energy -- who happens to be Barbie's father, Don (Brett Cullen)!
After not speaking for years, Barbie and Don come to an understanding; Barbie seems more grounded, more like an adult ... his late mother would be proud. His reservations notwithstanding, Don agrees to help Barbie with his one request: to get to the Dome. Pauline takes Sam to Lyle: he's in that same psychiatric hospital, repeating the name "Melanie" over and over. Could escaping the Dome have triggered this? Is Sam's quivering hand a similar sign? While Big Jim holds a memorial for Barbie at the diner, Melanie and Junior bring the egg to the tunnel; suddenly, it emits a "pink stars" picture of Zenith. Maybe the tunnel really is a way out! Pauline and Sam make up for lost time; inside her hospital classroom, we see a painting of a red door. Meanwhile, Barbie and Don walk past a similar door ... in the ground, right in Don's backyard!