When the nomadic beetle Rug Bug crash-lands outside of Mousetopia, he is offered assistance by the Dixies, a mouse-family residing in the city-state. Rug soon discovers the mice are forced to hand over a cheese-and-acorn tax each month to the notorious Fat Rat Bart and the Ratty Army. Following a run-in with Fat Rat Bart and his cronies, the Dixie family creates an underground movement to overthrow the rats. Hoping to bring freedom to his newfound friends, Rug Bug joins the fight.

But, when the initial uprising fails, Fat Rat Bart retaliates by capturing someone close to the rebels. The terms for the prisoner's release: Giving up the revolution. Undaunted, Rug Bug and the Mousetopians prepare for one final showdown with the Ratty Army for the liberation of Mousetopia.