Contains spoilers for this episode and earlier episodes.
Dipper's jealousy of Robbie turns into an argument while Wendy is away camping. After Dipper breaks his phone, Robbie challenges him to a fight in the park. Dipper knows he cannot win and hides in the arcade, where a secret input brings the fighting-game hero Rumble McSkirmish into the real world. Hoping to scare Robbie into backing down, Dipper recruits him as a bodyguard and invents a story that Robbie killed his father. Rumble accepts the revenge mission with far more enthusiasm than Dipper expects. At the Shack, Mabel notices Stan's fear of heights and devises her own plan to cure it.
Rumble attacks Robbie and refuses Dipper's orders to stop. He pursues him through town, damaging anything in his way, until the chase reaches a water tower where Mabel has brought Stan. Dipper admits that his story was a lie and that Robbie did not kill anyone. Rumble turns on him as the true enemy, forcing Dipper to face the danger he created. He endures the fighter's attacks until the game ends and Rumble disappears. Robbie chooses not to continue their original fight, and the boys agree to keep their hostility quiet for Wendy's sake. Stan survives the tower experience feeling cured, while Mabel discovers that the height has frightened her instead.