In this horror thriller, social outcast Willard Stiles (Crispin Glover) is haunted by the ghost of his dead father and trapped between the nagging of his aging mother (Jackie Burroughs) and the constant pressure of his domineering boss, Mr. Martin (R. Lee Ermey). The socially inept Willard is friendless, frightened and suicidal, seeking security anywhere he can find it. He is also bitter toward Mr. Martin, who aggressively belittles Willard. In the moment of his deepest distress, Willard discovers faithful friends in the rats found in his basement. When Willard finally cracks and strikes out against his oppressors, his faithful rats become a grotesque army of destruction and death.