After finding out that all of the nuclear plant's staff members had been informed of the plant's maintenance via e-mail, Homer decides to buy a computer. After he gives up on learning how to use it, Lisa sets up the computer. Homer eventually catches on and starts his own webpage, which contains copyrighted material from other pages. To avoid getting sued, Homer calls himself "Mister X". Late at night, unable to sleep until someone visits his page, Homer hears a rumor from Bart started by either Nelson Muntz or Jimbo Jones that Mayor Quimby spent the street repair fund on a secret swimming pool. He posts this rumor on his page, which is seen by several of Springfield's citizens.
Mayor Quimby is the subject of a city-wide scandal when a barrage of reporters find a luxurious pool along with many scantily dressed women in Quimby's office. Homer keeps his anonymity while posting more rumors and finds out Mr. Burns plans to sell plutonium to terrorists and is later arrested by the CIA. Eventually, Mr. X wins the Pulitzer Prize for his journalistic achievements, despite nobody knowing who he is. When he hears that the prize money will be given to starving children, Homer reveals that he is Mr. X.
However, this ends up alienating Homer from the rest of the town, as nobody feels comfortable confessing their secrets now that they know Homer's Mr. X, and his fame soon plummets. To boost his popularity, Homer begins posting outrageous stories on his webpage. His fame back, Homer celebrates by going to a fake Kwik-E-Mart, and ends up getting kidnapped.
Homer wakes up on the "Island", a place where the inhabitants are people who have been exiled from society for harboring dangerous secrets. Homer learns from the organization's leader, Number Two, that a story he wrote about flu vaccinations containing mind-control serum was true. The mind control drug is calibrated to drive people into a frenzy of shopping, which is why flu shots are administered shortly before Christmas. While Homer is trapped on the Island, he is replaced by a doppelgänger who looks identical to him but speaks with a thick German accent.
Number Six, who is trapped on the Island for inventing the bottomless peanut bag, tells Homer about a makeshift boat he spent thirty-three years making, which Homer steals and escapes the Island with, popping the Rover that emerged from the water to trap him. When he gets home, Homer tries to send out a message to the police through his computer, but is stopped by Number Two taking over the computer and is caught by his doppelgänger.
Homer fights his double and defeats him by kicking him in the crotch. His family is happy the real Homer is back, but then a fake Santa's Little Helper spouts a gas that drugs the entire family. The episode ends with everyone in the family enjoying their strange, new life on the "Island" (which Marge even saying that after getting used to the druggings, the Island itself is actually a "pretty nice place").