In the quiet, dysfunctional town of South Park, Colorado, four boys—Stan Marsh, Kyle Broflovski, Eric Cartman, and Kenny McCormick—sneak into an R-rated movie featuring their favorite Canadian comedy duo, Terrence and Phillip. The film is filled with obscene language and crude humor, leaving a significant impression on the boys. They emerge from the theater repeating the profanities they've learned, much to the horror of their parents and teachers. This leads to a moral panic throughout the town, with adults blaming Canada for corrupting their children and the children embracing the movie's vulgarity, spreading it throughout their school and community.

As the outcry against Canada escalates, Kyle's mother, Sheila Broflovski, spearheads a campaign against the country, leading to an international incident that threatens to escalate into full-blown war. Meanwhile, Kenny dies (again) after attempting a dangerous stunt inspired by the movie, landing him in Hell where he learns of a diabolical plan that could destroy the world. The boys, feeling responsible for the chaos, embark on a mission to rescue Terrance and Phillip, who are facing execution under the new authoritarian regime instigated by the parents' backlash. Their journey is fraught with challenges, both earthly and supernatural, as they seek to undo the damage they've inadvertently caused and save the world from an impending apocalypse, all while navigating their friendship and the absurdities of the adult world.