In this crucial segment, the hapless brothers, Bob and Doug McKenzie, find themselves in a hilarious predicament as they attempt to pass off their own lackluster film production as a legitimate cinematic experience. The situation quickly spirals into chaos when disgruntled audience members turn on them, compelling the resourceful duo to unleash a swarm of moths into the theater. This crafty diversion allows them to escape without issuing refunds—except for a sympathetic couple whose beer money had unfortunately been squandered on their tears. The following day, Bob and Doug hatch a daring scheme to extort free Elsinore beer from the local brewery by strategically placing a live mouse in an empty bottle, only to find themselves redirected to the management team. Their persistence ultimately pays off when they secure jobs inspecting for unwanted rodents on the bottling line.
However, a sinister force lurks in the shadows; Brewmeister Smith is the mastermind behind a dangerous plot to dominate the world by tainting Elsinore beer with a mind-altering substance. This nefarious brew renders its victims compliant and susceptible to mind control through specific sonic frequencies. Smith conducts his insidious tests on unsuspecting patients at the nearby Royal Canadian Institute for the Mentally Insane, conveniently linked to the brewery by an extensive network of tunnels.
As Bob and Doug dig deeper into the secrets surrounding the Elsinore brewery, they uncover an intricate web of intrigue. The mysterious death of John Elsinore, the brewery's former owner, looms large, with his daughter, Pam, now running the show. During their exploration of the extensive complex, they stumble upon an abandoned cafeteria housing an ancient Galactic Border Patrol video game, which unexpectedly reveals that Brewmeister Smith orchestrated John Elsinore's murder and ensnared Pam's Uncle Claude in the plot. A keen observation from Bob identifies a brewery employee, Jean "Rosie" LaRose, a former hockey player who tragically fell prey to Smith’s mind control after suffering a career-ending nervous breakdown.
By a twist of fate, Bob and Doug inadvertently enter Brewmeister Smith's inner sanctum while he is briefly distracted. In a moment of absent-mindedness, Doug mistakenly grabs a floppy disk containing shocking video evidence of John Elsinore's murder, thinking it to be a bootleg recording. This innocent error sets off a chain reaction leading to their eventual trap. Smith and Claude cleverly tranquilize the brothers and manipulate their downfall, secretly stashing Pam and her father’s friend, Henry Green, inside beer kegs in the back of their compromised van, instructing the unsuspecting duo to deliver these mysterious containers to a party. Helpless to resist their manipulated fate, Bob and Doug embark on a wild goose chase that culminates in them careening into Lake Ontario, emerging unscathed—though Pam is left with apparent memory loss. The authorities soon apprehend the brothers.
Their absurd antics in court ultimately convince the judge that they’re certifiably insane, sentencing them to the clutches of Brewmeister Smith at an asylum. Rosie soon tracks them down and orchestrates an ingenious escape, reuniting them with Pam as they unveil Smith's malevolent plan. In a thrilling twist, Rosie incites a rebellion among the brainwashed patients, leading to a split between the brothers for the first time in their lives. Doug allies with a group of asylum inmates to capture Claude, while Rosie and her team overpower Brewmeister Smith. As John Elsinore's ghost haunts the brewery's wiring, it exacts a fitting punishment by electrocuting Smith when he's forced against his glowing world map.
Meanwhile, Bob and Pam find themselves trapped in a brewery tank filled with beer, which Bob begins to consume with reckless abandon, leading to an exaggerated inflation of his body. John Elsinore's spirit warns them that Smith has already dispatched tainted beer to Oktoberfest, urging the brothers to act quickly to prevent its consumption. The authorities accompany the McKenzie Brothers back to their home to retrieve their cherished dog, Hosehead, who unexpectedly becomes the unwitting hero when he leaps into the air, resembling Superman. Mistaken for a skunk, he sends the attendees fleeing from the contaminated beer, ultimately saving the day. In the end, the McKenzie Brothers are celebrated as heroes, while Pam and Rosie discover true love. Bob and Doug are allowed to cart away the toxic beer, seemingly intent on drinking it dry. The movie concludes with a humorous over-the-credits commentary where Bob and Doug reflect on their cinematic adventure alongside select crew members, whose names adorn the credits.
