Willard Stiles (Crispin Glover) is a social misfit taking care of his ill and fragile but verbally abusive mother Henrietta (Jackie Burroughs) in a musty old mansion that is also home to a colony of rats. Willard finds himself constantly humiliated in front of his co-workers by his cruel boss, Frank Martin (R. Lee Ermey), a vicious man who assumed control of the company from Willard's father upon his death by suicide, and whose professional interest in Willard extends to a personal financial one. A co-worker, Cathryn (Laura Elena Harring), has sympathy for the quirky Willard. Cathryn becomes Willard's friend and love interest.