At Julia's house, Barbie enters his room and finds Melanie going through his belongings. He demands answers and the girl says that she's looking for something that will tell her where she remembers him from. Julia comes in and is angry that Barbie is interrogating Melanie, who insists that she remembers nothing about her past. Once Melanie leaves, Barbie thinks that the girl is faking her amnesia and heads to the diner for Big Jim's mandatory citizen registration. Melanie comes back and asks if she can go with Julia and see someone she knows, and Julia agrees, saying that they'll figure out her past.
Big Jim goes to the barbershop to get a shave from an old friend, Lyle Chumley. They talk about how Big Jim is meeting with Rebecca and wants to looks his best, and Big Jim thanks Lyle for his support when Pauline died. When Lyle smiles to himself, Big Jim asks what he's happy about and Lyle says that it seems like an auspicious day. Big Jim goes to the diner and hands out the questionnaires, explaining that they're to determine what resources everyone needs. Joe and Norrie come over and Julia tells Joe that they'll find Angie's killer. The boy is concerned that they now only have three of the four hands that the Dome required. He wonders why the Dome didn't protect Angie, while Lyle helps hand out questionnaires.
Rebecca asks Joe to go to the high school to get the model windmill that they built, so that they can make a full-scale model to provide Chester's Mill with electricity. Norrie refuses to go, saying that she isn't a student, and Rebecca tells her that school is now mandatory for all teenagers. Melanie is checking everyone out but doesn't see anyone that she recognizes, and volunteers to go with Joe. Norrie goes with them and Julia notes that Rebecca is taking charge. The teacher says that she is only doing so at Big Jim's request.
At Sam's cabin, Junior tells his uncle about how he found Angie's bracelet under his cot. He worries that he may have killed Angie without remembering it, but Sam assures his nephew that he wouldn't kill someone he loved. The former paramedic says that Junior's mother Pauline also suffered from blackouts, and that when she went back to where one happened, she could sometimes remember what happened. As Junior goes to his car, Sam assures him that they'll figure things out together as a family, while storm clouds form overhead.
At the diner, the townspeople spot the coming rain and Big Jim has everyone grab bowls so they can gather drinkable water. However, when they head outside, they realize that the rain coming down is blood red.
At the high school, Joe, Norrie, and Melanie see the rain. When Melanie reaches out to touch it, they realize that it's acid rain.
At the diner, the townspeople reach the same conclusion and everyone takes shelter inside. Lyle tells Big Jim that they're suffering through the Ten Plagues of Egypt from the Bible: first a plague of locust, now a rain of blood. Rebecca insists that it's some kind of spore contamination in the water but Lyle figures that he'll rely on scripture for his explanation. Sam brings an injured woman in and says that there are more people trapped in the rain, and Barbie and Julia volunteer to go with him.
Joe and the others find Junior roaming the hallway and he refuses to tell them why he's there. They realize that he's been there since before the rain fell since he doesn't know about it.
Big Jim and Rebecca drive out into the country and Big Jim wonders if the Dome is testing him. Rebecca assures him that there's a scientific explanation for everything that has happened to them, and that she'll believe in him if he believes in her. A man in a raincoat steps out onto the road and Big Jim is forced to swerve into a tree to avoid him. The man pulls Big Jim out of the car and drives off in it, and Big Jim tries to protect himself against the acid rain.
At the school, Melanie wonders if Junior is okay as he stares out the window. She then checks on Joe, who is focused on checking the science class' tablets and finding the windmill specs. As Norrie gets another tablet, Joe starts his and realizes that he's getting email.
Joe uses his radio to call for help.
Norrie confirms that she can get the Internet as well and discovers that a group called the Hounds of Diana is monitoring them closely. Joe finds an email from his father, who tells him to take care of Angie. Joe wonders if he should tell his parents that their daughter is dead, particularly when none of them may ever get out from the Dome. Melanie assures him that they'll figure something out, while Norrie glares at her. She gives a tablet to Junior and suggests that he check his email, and when he does he discovers an email from the Hounds of Diana. They say that they can help her, and have an attachment that asks what Pauline's birthday is.
Barbie, Sam, and Julia take an ambulance to Big Jim's location and discover that he's unconscious, possibly from anaphylactic shock.
Rebecca wakes up inside the Chester's Mill cement factory and realize that her captor is Lyle. He's tied her to a chair and admits that he doesn't know if Big Jim is alive or dead. He figures the rain will spare Big Jim if he's a righteous man, but doesn't hold out much hope for him. Rebecca asks her captor to untie her, saying that she can stop the rain, but Lyle says that neither he nor the Dome want the rain to stop. He talks about how Yahweh sent the Ten Plagues against the unbelievers in Egypt, and that the Dome is doing something similar to Chester's Mill. Lyle tells Rebecca that she has a choice to make and he hopes that she will make the right one, then puts on his raincoat and walks outside.
When they get Big Jim back to the diner, he wakes up long enough to tell them that Lyle took Rebecca.
Lyle comes back with a bowl of rainwater, unaware that Rebecca has started to loosen the ropes holding her. He says that he can't let her stop the rain, and when it ends on its own then the Rapture will occur and the righteous will go to Heaven. Rebecca says that he won't stop her, and Lyle holds up the bowl and says that he's going to baptize her.
Junior enters the birthday and discovers a video message from his mother Pauline, alive and well. She says that she hope to see him again and tells him that he should only talk to Lyle about any questions that he has. The connection suddenly stop and Joe figures that there is a block. Junior leaves, telling the others that he has to find someone, and drives off before they can stop him.
Barbie and Julia search Lyle's barbershop for any clue to where he took Rebecca. The couple argue about whether the townspeople will display their worst qualities as they remain trapped. Julia insists that people will eventually choose good over self-interest, but Barbie isn't convinced. He finds a childhood photo of Lyle, Sam, and Pauline as children in 1988, holding hands. Julia calls Sam to ask what he knows about the photo, and he confirms that Lyle was seeing Pauline at the time. However, he didn't even remember it until Julia called to tell him, and he says that he hasn't spoken to Lyle since Pauline died and has no idea where he might have taken Rebecca. Junior comes in, having overheard them on his police radio, and confirms that the photo was taken at the cement tower outside of Chester's Mill.
Joe is still unable to get the Internet signal back and suggests that the magnetic disruption in the Dome may have caused a wormhole to let signals through. Melanie eagerly agrees to go with him and Norrie irritably tags along to keep an eye on her.
At the diner, Big Jim wakes up and finds Sam at his side. He wonders why Sam saved his life, and Sam says that he doesn't plan to let him die—yet—no matter how much he hates him.
At the cement factory, Lyle pours some of the acid rain down Rebecca's back. She quickly agrees to accept the repentance of the Dome, but Lyle doesn't believe her. He figures that he's a lost cause and prepares to shoot her rather than waste any more time. Barbie and Junior burst in, guns drawn, with Julia behind them. Lyle uses Rebecca as a shield and threatens to shoot her if they don't drop their guns. They do, but Julia steps forward and says that the Dome talks to her. Lyle admits that he knows what the Dome wants him to do but doesn't speak to him, and he asks Julia what the Dome tells her. As she moves closer, Julia says that the Dome wants us to earn the light, and asks him to help her by giving her the gun. As Lyle starts to hand it over, Rebecca pulls her hand free, grabs the bowl of rainwater, and throws it in Lyle's face. Barbie and Junior easily disarm her. When Julia points out that Lyle was going to surrender, Rebecca ignores her and leaves.
At the school, Joe follows the signal using his tablet to measure its strength. The signal is coming to the locker next to where someone murdered Simon, and Joe hesitates to approach the crime scene. Melanie tells him not to be frightened and an angry Norrie says that she's not Joe's girlfriend and should butt out. As she and Joe argue, Melanie touches her hand to Angie's bloody handprint and then dials the combination on the locker. She unlocks it and Joe opens the door, only to discover that the locker is empty. He confirms that the signal has disappeared, while Norrie demands to know how Melanie knew the combination.
After mixing some salination with high pH compounds, Rebecca has some men pump the mixture into the lake. The rain soon stops and Rebecca checks on Big Jim at the diner. She explains that Lyle is in jail and that she was the one who stopped the rain. However, she warns him that the rain has only made things worse for Chester's Mill. Nearby, Julia hears them talking and asks Rebecca what she means.
At the school, Norrie demands that Melanie drop the innocent act and explain how she knew the combination. Melanie says that she saw it in the head and shoves Norrie away, and Joe says that he knows how Melanie saw the combination.
After the customers leave the diner, Rebecca talks with Big Jim, Barbie, and Julia, and tells them that thanks to the rain, most of their remaining resources have been destroyed. She suggests that they come up with a contingency plan to deal with the dwindling resources, and Julia realizes that the mandatory questionnaire was a way for them to pick those least likely to survive and help the town. Julia tells Barbie to come with her, but he stays put and says that they're just discussing contingency plans. She keeps going and Barbie follows her, insisting that he isn't taking anyone's said. Julia reminds him what he said earlier about how people becoming their worst in a crisis, and Barbie warns her that faith will only get them so far. Disgusted, Julia tells Barbie not to follow her and leaves.
Sam goes to the jail and visits Lyle's cell, and finds him singing. He points out that he could kill the barber and no one would know or care, but Lyle is confident that he won't. Sam reminds him that he told him to lie low when the Dome came down and let him take the leader, but Lyle says that he has a different leader now. Undeterred, Sam says that Lyle promised to make sure that what they buried stayed buried. However, Lyle tells him that when the Dome came down, all bets are off. He says that the Dome will deliver them to another place, but Sam tells him that the opposite is likely to happen. Irritated, Lyle says that he's done talking and lies down on his cot… unaware that Junior is watching them on the security camera.
At the diner, Rebecca warns Big Jim that if they sacrifice one-quarter of the populations, the other three-quarters could survive. She says that the decision is too big for her to make, and that the Dome chose Big Jim to decide... and he has to do so before it's too late.
Junior waits until Lyle is alone again and then goes to see him. Rattling his baton on the bells, he demands answers and says that Pauline told him to see Lyle. Lyle says that he won't say anything until Junior releases him.
Joe goes to the filing room and pulls the school records for who owned the locker. Melanie's name is listed for the year 1988, and they pull the yearbook for 1988. Inside is a photo of Melanie, who hasn't aged in 26 years.