Everybody in Springfield (Except the Flanders) have had enough of the Simpsons' shenanigans, and decide to banish them from town. The family settle in a deranged town, where they pick up new skills like Maggie hunting with a crowbar. Lenny and Carl miss the family and decide to pay a visit. Soon, everybody in Springfield decides to rebuild Springfield where the Simpsons live now.
The Simpson family are at home watching Channel 6 News where Kent Brockman announces that there is a disaster and that everyone has to go into their underground bunkers. After saying it was a drill, and then acting like there was an actual disaster again, he tells everyone to go into their shelters for three hours and not to come out. The Simpsons head to their shelter.
After a while, the family is all bored and decides to head out of their shelter to explore Springfield while it is empty. They then go to Springfield Town Hall where they realize that there is a secret meeting going on. They sneak in to find that the town has voted to kick them out of Springfield. After making themselves known to the rest of the town, the townspeople act angry at them. Mayor Quimby reveal that the town has gone bankrupt due to their family's shenanigans over the years. He mentions it was a mixture of Homer's recklessness, Bart's vandalism in school and in town, Lisa's environmental pleas (though much cheaper, yet was very annoying) and Marge's attempts to see the family in a positive light that got them kicked out. Even Mayor Quimby declared Marge to be the "worst Simpson of all." Offended by this, Ned attempts to defend them and tells the citizens to give the Simpsons a break. Quimby, however, had planned Ned's arrival in advance, and ejects him from the meeting, after which Ned withdraws his objections. The Simpsons are then paraded out of Springfield during a big celebration that the Flanders refuses to attend, still angered how the residents are acting like pariahs themselves.
After driving for a while, Bart says that he needs to pee. They stop to let him go and are then held up by a guy with a shotgun. After Marge explains their situation to him, he welcomes the family to The Outlands. The family starts new here and enjoy life more, but Marge is having a hard time settling in. They find a new neighbor with the creator of WikiLeaks, Julian Assange. When Homer, Bart and Lisa confronts Marge about her lack of effort in settling in the Outlands, they come to the realization that she is homesick for Springfield. She voices her concerns that Maggie is falling in with the wrong crowd. Marge also admits to missing Ned's cheerful personality and Helen Lovejoy of Springfield critiquing her brownies. Despite Bart's warning to stay away by reminding Homer that they're in exile, he decide to cheer Marge up by sneaking her back into Springfield.
Homer and Marge, disguised as Mr. Burns and Waylon Smithers, sneak back in, presumably tricking Chief Wiggum in the process. They have a romantic night together then head to their old home where they go to bed. In bed, they hear Jimbo, Dolph and Kearney come in and are found out. Before the bullies can tell anyone, the police come to the house along with the rest of the town. Chief Wiggum tells Homer and Marge that he had seen through their disguises and pretended to be fooled in order buy himself time to gather the residents together.
Marge is nervous but Homer sarcastically remarks what the residents of Springfield intend to do about it, "Throw us out again?". In response several residents suggest a number of heinous punishments, including getting the family a subscription to the opera (because they don't like it). When Gill suggest that they shoot the Simpsons, Wiggum and the other cops prepare to do just that.
These actions make Marge furious, and she tells them not to bother shooting them. She then admits that while their new home isn't perfect it does have one thing Springfield doesn't. Homer agrees, and reveals that is "non-jerks", thereby insulting the residents of Springfield for their attitude, trying to arrest / shoot them and exiling the family in the first place. This criticism visibly shocks the residents of Springfield. Marge adds that she just wanted to visit her house because she was homesick but upon realizing how much the residents of Springfield hate both her and her family (minus the Flanders), she prefers to return to her home in the Outlands, where her new community accepts the Simpsons for who they are and the family is free to love each other without the constant spite and judgement from their former neighbours.
Marge is finally settling into life in The Outlands until Lenny and Carl, turn up. Bart and Maggie acts hostile towards them, claiming they were part of the crowd who exiled them. Carl explains that after hearing what Homer and Marge said, they wanted a better life as well as a fresh start. Eventually, Moe turns up too, opening Moe's Cavern which they and Homer patronize at. After that, Mayor Quimby, and many other Springfield residents show up, wishing to abandon their lives in Springfield and start over in The Outlands. Soon, all of Springfield moves there to start new lives with the Simpsons and they begin rebuilding a new city. The man whom the Simpsons befriended decides to pack up and move further away from the people. Eventually, Seymour Skinner is the last person left in Springfield, until Bart rescues him in a wooden helicopter, crashing him into several buildings and landmarks.
At the end of the episode, a title card appears stating: "Thanks for 500 Shows. All we ask is that you go out and get some fresh air before logging on the Internet and saying how much this sucked."