Desperate for companionship, the repressed Willard (Crispin Glover) befriends a group of rats that inhabit his late father's deteriorating mansion. In these furry creatures, Willard finds temporary refuge from daily abuse at the hands of his bedridden mother (Jackie Burroughs) and his father's old partner, Frank (R. Lee Ermey). Soon it becomes clear that the brood of rodents is ready and willing to exact a vicious, deadly revenge on anyone who dares to bully their sensitive new master.