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. He mentions it was Quimby's own corruption in his reckless spending that lead to the town's bankruptcy. However, this serves to further anger the residents and reveals the Flanders family as the only residents who voted against exiling the Simpsons. Quimby tells Ned off that his attempt to defend the Simpsons reveals his family own corruption and intentionally ejects the Flanders out of the hall. Before his family leaves, Ned warns the delusional residents that they'll regret exiling the Simpsons one day. 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. When introduced to their new neighbor and creator to WikiLeaks, Julian Assange, he is friendly with Homer and the kids. However, he is very rude to Marge and she dislikes him for it. 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 the women 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. He and the other cops are prepared to arrest them, but Homer is upset. He calls the crowd jerks for trying to arrest them just because they wanted to visit Springfield, but the residents are unmoved by his crude nature in insulting them. Upon realizing how much they hated the Simpsons (minus the Flanders), Marge is furious and tells them off to not bother arresting them. She admitted that after knowing the truth, Marge prefers to return to the Outlands because her new community accepts the Simpsons for who they are and the family is free to love each other without the constant spite and judgment from their former neighbors. Homer and Marge leaves for their new home, leaving the townspeople to start having second thoughts on kicking the Simpsons out, especially Smithers, Lenny and Carl when they realize that the Simpsons had accepted their homosexuality.
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 too. Lenny admit Springfield wasn't the same after the Simpsons were exiled out of the town and he along with Carl wants 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. Mayor Quimby names it Springfield, which Marge is truly against stating it takes away the charm of being known as The Outlands and has always disliked the corruption from the old Springfield. 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."