It's Halloween and the entire town is getting into the Halloween spirit; much to Zim's dismay because he considers the entire concept to be insane and he doesn't want filthy Earth children coming to his house. Meanwhile, Ms. Bitters sends Dib to an insane asylum because he has been acting crazier than normal, in which in truth he has been getting sucked into a nightmare world that was created due to his meddling with one of his father's inventions. After finally getting out of the nightmare world and out of the insane asylum, Dib sees Zim's house and decides to force Zim to come with him into the Nightmare world because he believes Zim will have the capability to put an end to all the madness, but will they manage to work together despite the fact that they're enemies and that Zim didn't want to help him in the first place?