In a small Canadian town, bumbling brothers Bob and Doug McKenzie are on a mission to get free beer. They concoct a plan to claim they found a mouse in a beer bottle, hoping to leverage it for free supply from the Elsinore Brewery. Once at the brewery, they stumble upon a sinister plot led by Brewmeister Smith, who is using a mind-controlling drug in the beer to take over the world. The brothers inadvertently get involved in an investigation about the brewery's suspicious activities, supported by Pam Elsinore, the brewery's rightful heiress, and police inspector John.

As Bob and Doug dig deeper, they uncover Brewmeister Smith's plan involving the use of electronic music to control the drugged consumers. Their journey takes them through various comedic situations, including escaping near-death events and outsmarting security guards. The stakes rise further as they discover more layers of the conspiracy, leading them into a battle against the nefarious forces at play. Through sheer luck and their unique brand of wit, the brothers strive to expose the truth and save their town from total control.