Marge is embarrassed at a Parent-Teacher Association meeting because she does not have an e-mail address. She decides to buy her own computer and is quite taken by the Internet. Quickly becoming bored with her lack of email messages she repeatedly hits the refresh button causing new advertising banners to appear. A banner ad for a MMORPG called Earthland Realms catches her attention. Marge clicks on it and soon creates a character for the game. She begins exploring the local town and interacting with game personas, all of whom are Springfield residents including Apu the gem trader, Seymour Skinner the turkey, Moe who looks like a troll but is not, Mrs. Krabappel the enchantress, Snake the Cobra King, Chief Wiggum the pig man, Smithers the Barbarian, Comic Book Guy the fully armored crusader-like warrior, and Sideshow Mel as a creature who looks surprisingly like a Tauren. Suddenly, everyone hides as a knight named "The Shadow Knight" appears riding a menacing black horse. The Shadow Knight is the most powerful and deadly character in the game (as Moe remarks "He once beat me to death with my life bar!"). While offline Marge walks by Bart's bedroom door. She unintentionally hears Bart say "Another senseless killing by the Shadow Knight" and realises that Bart is the Shadow Knight.
Meanwhile, Homer referees Lisa's soccer game. His subpar skills frustrate Lisa. Stung by her criticism, Homer learns the rules of soccer and becomes a better referee, briefly impressing Lisa. Lisa twice pretends to be fouled hoping that Homer would grant her penalties. Initially he does. When soccer star Ronaldo points out that Lisa is a "flopper" Homer gives Lisa a yellow card. Angry, Lisa rips up the yellow card, causing Homer to give her a red card for unsportsmanlike conduct and to eject her from the game.
Back in the MMORPG, Marge goes to the Shadow Knight's castle and meets Milhouse who is cursed to look like a female servant as a result of an evil spell. Marge constantly frets about Bart and, to Bart's dismay, redecorates his "trophy room" with the Hello Kitty expansion pack. In a fit of rage Bart smashes many of the decorations with a mace. In the process he accidentally kills Marge's character which severely disappoints real world Marge.
Homer and Bart go to Moe's Tavern to escape the troubles that have occurred with Marge and Lisa. Moe gives them surprisingly good advice about their situations. Homer jokingly asks "What have you done with the real Moe?" and everyone laughs. A cutaway shot reveals that the real Moe is bound and gagged in the room next-door. Acting on fake Moe's advice, Bart makes up for killing his mother's character by reviving her with two-thirds of his life force. Revived, "Elf Marge" tends to the Shadow Knight, however other characters raid the castle to take advantage of his weakened state. The other characters brutally kill the Shadow Knight. In a rare breach of character Bart is blasé about his character's death. He decides to go outside and play.
In the real world Homer enters Lisa's room. He offers her a BBC documentary produced in cooperation with Canal+ about "floppers", hoping that she will forgive him. Watching the documentary Lisa realizes it was she that was at fault. Instead of forgiving Homer, Lisa apologizes for her injustice against him. Homer, Bart, Lisa and Maggie play a game of soccer in their back yard however Marge continues gaming inside. Feeling sorry for Bart, Marge dons the Shadow Knight armour and begins a revenge campaign for him starting with Moe's character. Marge juggles Moe's character head like a soccer ball. As he is being beat up Moe comments on why he pays $14.95 a month to play the game.