At the airport, Bart and Homer meet Glen and Jane, recruiters for the new religious movement, Movementarianism. They invite Homer and many Springfield residents to watch an orientation film. The film explains over many hours that a mysterious man known only as "The Leader" will guide Movementarians aboard a spaceship to the planet Blisstonia, where they will live in everlasting happiness. The lengthy film brainwashes most of the attendees into worshipping The Leader, but Homer does not pay enough attention to be affected. After trying other methods, Glen and Jane finally convert him by singing the theme from Batman, replacing the word "Batman" with the word "Leader".
After Homer joins the cult and signs over his savings and house, he moves his family to the Movementarian compound, where everyone is forced to harvest lima beans. The Leader lives in a "Forbidden Barn" where the spaceship is supposedly being constructed. He only appears briefly, waving to his followers from a Rolls-Royce. Movementarianism's power and popularity grow; the local Presbylutheran church empties, and the cult takes over the city's media. Montgomery Burns decides to start his own religion, jealous of The Leader's tax-exempt status, and declares himself a god at an elaborate ceremony at the Springfield Nuclear Power Plant. Watching Springfieldians are unimpressed, however, after Burns' muscle-bound wax outfit catches fire in a pyrotechnics display.
Though defiant at first, all the Simpson children are converted to Movementarianism. Marge is the only family member to resist, and escapes from the heavily guarded compound, especially The Monster Bubble. Outside, she finds Reverend Lovejoy, Ned Flanders, and Groundskeeper Willie, who have all resisted the Movementarians, and with their help, she tricks her family into leaving the compound with her. At Flanders' home Marge deprograms her children by pretending to offer hover bikes. Homer seems to yield after Ned offers him a beer, but just as the first drop lands on Homer's tongue, he is captured by the Movementarians' lawyers.
Back at the compound, Homer reveals to a crowd of Movementarians that he is no longer brainwashed. Homer opens the doors of the Forbidden Barn to expose the cult as a fraud, but he and the crowd are surprised to find "one hell of a spaceship" inside. The Leader proclaims that, due to Homer's "lack of faith", humanity will never reach Blisstonia. The Springfieldians fear that The Leader is correct but the crude spaceship disintegrates in flight, revealing The Leader on a pedal-powered aircraft fleeing with everyone's money. The crowd's faith is broken but The Leader does not fly very far, crashing on Cletus Spuckler's front porch. Cletus takes the town's money from the Leader at gunpoint.
As the Simpsons return home, Lisa remarks, "It's wonderful to think for ourselves again." Then, the family becomes hypnotized by a Fox television commercial, however, which declares, "You are watching Fox." In unison, the family responds, "We are watching Fox...", causing them to be brainwashed.