The movie begins with Owen and her mother at the local high school, Void High School, on vote night. It's established that Owen has asthma and after they place their vote Owen wanders around the school and eventually comes into the cafeteria where the deinflated inflatable planetarium lays on the ground. At the end of the room Maddy is sitting reading their copy of The Pink Opaque episode guide. Owen goes to ask them about the book, and Maddy explains bits of the show to her, that Isabel and Tara are the Pink Opaque, that they met at a sleepaway camp, that they have a psychic connection where they can communicate via 'the psychic plane' and that they fight monsters sent by the villain Mr Melancholy together from across the country to save people from being trapped in a prison called 'The Midnight Realm'. They both have a tattoo on their necks of a pink ghost with 2 circles which are either eyes or glasses. They tell Owen how much they love the planetarium and how it feels like the school becomes someplace else on election night and that Owen should watch the show, but it's on after her bedtime so Maddy convinces her to come for a sleepover.
Owen asks her mother to have a sleepover round another kid, Johnny Link's, house. When her mom drops her off and leaves she instead walks to Maddy's house where them and their friend are getting ready to watch The Pink Opaque together. She comes in and watches the episode with them and she is immediately sucked in by the show. When it ends she stays at Maddy's house and they talk about the show. Maddy tells Owen that, sometimes, The Pink Opaque feels more real than real life, and then they both go to bed. When Owen is walking back the next morning she imagines Isabel walking through the trees at the sleepaway camp looking happy and content.
2 years later, Maddy has been leaving tapes of the episodes for Owen in the darkroom at the school so that she can watch the show. Owen claims that she never had the courage to talk to Maddy much after the first sleepover, though it is later shown that they did see each other more than she lets on. Owen goes to talk to Maddy on the bleachers at the school and she asks if they still talked to their old friend, but Maddy replies that they haven't talked to her in a year because she outed them as a lesbian and claimed that they tried to touch her chest. They ask Owen if she likes boys or girls, and Owen responds that thinking about it makes her feel like she's taking a shovel to her insides and that she's too scared to open herself up and check. Maddy says that maybe she's like Isabel, "Afraid of what's inside" her.
Owen comes for another sleepover at Maddy's house and Maddy breaks down crying in the middle of the episode of the Pink Opaque that they're watching. When the episode ends Maddy tells Owen about their plan to run away from home and that they'll "die if I stay here". Owen is upset because then she wont have anyone to watch The Pink Opaque with and Maddy comes to sit with her and draws the pink opaque tattoo on the back of her neck. They tell her to run away with them. However, Owen is too scared and scrubs the drawing off of her neck in the morning. She comes clean to Johnny Link's mother about pretending to stay at their house. Days later, Maddy disapears and all they leave behind is their TV set burning in the back garden.
Years later in 2006 Owen still lives with her father, her mother has died of cancer and she works at a local movie theatre where she looks even more distant than before. On the way home from work one night she comes across a downed powerline with pages of The Pink Opaque episode guide scattered around it, all with descriptions of the never filmed season 6. While picking up groceries Maddy reappears and they take Owen to a local bar where they explain that they've been inside of The Pink Opaque, that they are Tara and Owen is Isabel and that they need to go back there together. Owen leaves but agrees to meet Maddy at their old high school. Owen rewatches the season 5 finale that night. In it, Mr Melancholy lures Isabel back to the sleepaway camp where Tara is calling for help, but when she gets there Tara had already been captured. Mr Melancholy feeds her the luna joice, which will trap her in the midnight realm, and then his minions burry her alive. After watching it Owen tries to shove her head inside of the TV but her father pulls her out and shoves her head over the bath, full of boiling water. Owen screams how this isn't her home and how Frank isn't her father.
She meets Maddy inside of the inflatable planetarium in the gym a while after this and Maddy explains that they lived all around America but no matter where they went everything still felt wrong, like time wasn't moving right. Eventually they paid someone to bury them alive. When they dug their way out they found that they were Tara again, back at the sleepaway camp. They explain that them and Owen/Isabel need to bury themselves alive again so that they can escape being trapped in the midnight realm. After hearing the story Owen says that Maddy's story is insane but follows them out to the field. At the last minute she tackles Maddy/Tara to the ground and runs away. Owen locks herself inside of her house because she's scared of Maddy coming back to force her underground, but in the years after she still wonders if they were right and she was really somebody else. She gets married and has children, who she says she loves very much. When she decides to rewatch the Pink Opaque it seems nothing like it was before and she dissasosiates watching it.
Years later, Owen is working at an entertainment place still living in the same place as she did before and her asthma has gotten very bad. While helping celebrate a child's birthday party she breaks down crying and screaming and rushes to the bathroom. When there, she takes a box-cutter and cuts open her chest where she see's TV static and looks genuinely happy. She leaves and starts apologising to everyone for getting upset and the movie ends.