In a parody of the classic American road trip, aimless teenage slackers Beavis and Butt-Head awaken one morning to discover their most prized possession—their television—has been stolen from their living room. Believing that a television equates to ultimate manhood, they embark on a misguided quest to replace it. Wandering into a shady motel, they are mistaken by a disgruntled criminal named Muddy Grimes for hardened professional assassins. Muddy offers them a thousand dollars each to "score" with his estranged wife, Dallas, who he also wants permanently eliminated. Misinterpreting Muddy's instructions entirely as a euphemism for
sexual intercourse, the enthusiastic duo eagerly accepts the hitman contract and boards a flight to Las Vegas, completely oblivious to the chaos they are about to unleash.Upon arriving in Vegas, Beavis and Butt-Head meet Dallas in a luxury hotel suite. Dallas, who secretly plans to double-cross her husband by stealing a stolen biological weapon hidden inside a rubber novelty toy, immediately recognizes the boys' supreme stupidity. She slips the dangerous device—a modified smallpox-carrying sphere—into Beavis’s pants, telling him it is a special game. She then ditches them, sending the dimwitted pair careening across the American landscape on a chaotic cross-country bus tour. Meanwhile, a relentless ATF agent named Fleming relentlessly pursues them, convinced the teenagers are mastermind terrorists orchestrating a catastrophic biological attack on the United States.Unaware of the apocalyptic weapon they are lugging around, the boys endure a series of misadventures, hitchhiking with an assortment of eccentric travelers, including an aging hippie duo who turn out to be Beavis's and Butt-Head's biological fathers. Their journey leads them to Washington, D.C., where Fleming finally corners them at the White House. During the tense climax, Beavis consumes excessive amounts of caffeine and sugar, transforming into his violent, chaotic alter ego, Cornholio, which inadvertently triggers mass panic among government officials and security forces.As the situation escalates, Muddy Grimes catches up with the boys, intending to kill them for failing to perform the hit. However, a massive standoff ensues involving the ATF, Dallas, and Muddy. Dallas attempts to retrieve the biological weapon, but the boys accidentally hand it directly to ATF Agent Fleming, who safely secures it, averting global disaster. Ultimately, Muddy is arrested, Dallas’s
criminal conspiracy is dismantled, and the boys are cleared of terrorism charges due to overwhelming evidence of their absolute idiocy. Returning home to Highland, Texas, Beavis and Butt-Head are miraculously reunited with their stolen television, which has been recovered by local police, bringing their absurd odyssey to a triumphant, brain-dead conclusion.