The Simpson family is advised of a citywide nuclear safety drill and all the inhabitants of Springfield are told to stay in their basements for three hours. The family members quickly become bored in the basement and decide to leave the house and go see the empty city. As they walk through Springfield, they see an unusual number of cars parked by the City Hall. The Simpsons go in and discover that everyone in town has gathered for a secret town meeting and have voted unanimously to kick them out of Springfield forever. Mayor Quimby reveals that the city has gone bankrupt due to the constant cleaning up of the family's shenanigans over the years, ranging from Homer's drunken antics, Bart's various pranks, and Lisa's environmental concerns. Marge delivers a heart-felt plea to the residents to let the Simpsons live in the one place they call home, but they refuse, with Quimby declaring her the "worst Simpson" for always trying to see the family in a positive light.
A big celebration is held by the city's population as the Simpsons are officially evicted from Springfield. When the family drives out into the middle of nowhere at night with no place to stay, they come across a man who takes them to a county called The Outlands, which is a dirty, run-down place where there are no rules and regulations. The Simpsons settle in The Outlands and meet Julian Assange—their unfriendly next-door neighbor who operates the WikiLeaks Headquarters there.
While the rest of the family gets used to their new home, Marge becomes homesick. Homer sneaks her back into Springfield one night under the disguise of Mr. Burns and Smithers, and they spend the night getting drunk and having sex in their old abandoned home. However, Chief Wiggum sees through their disguises, and rallies the people of Springfield to the Simpson home to capture Homer and Marge. Marge is initially angry at the members of the mob, but she stuns them by saying that she does not want to live in Springfield or deal with them anymore, having found a place to live where she and her family can be accepted for who they are and love each other without worry of hate and judgment from others. Marge and Homer march through the visibly disillusioned crowd and return to The Outlands. Back in the Simpsons' new home, Bart discovers Lenny and Carl sneaking in. They tell the family they long to start a new life in The Outlands. Soon, Moe, 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 which they name Springfield.