Life has become one big trap for 30-year-old Willard Stiles (Glover). Haunted by the ghost of his dead father and suffocated by the psychological cord that keeps him tied to his mother in their once stately home, Willard floats through life, unable to connect with those around him. An office clerk at Martin-Stiles Manufacturing, Willard only has a job because his late father made it a condition of his partnership with Frank Martin (Ermey), who reminds Willard of this burden on a daily basis. But Willard has made an eerie discovery: he shares a powerful bond with the rats that dwell in his basement. Suddenly, Willard has friends - hundreds of them.
A beautiful office temp, Cathryn (Harring), brought in by Mr. Martin to cover for Willard’s alleged incompetence, lends an understanding hand. But even she takes a back seat to Socrates, Ben, and the rest of the legion of rats that begin to infest the basement of the Stiles home and whom, seemingly even more vulnerable than himself, Willard is unable to kill.
As the pressures upon Willard build and build, the foundation of his life begins to crack and the walls threaten to come crashing down. When Willard’s world is turned upside down by tragedy, those responsible must answer to his rapidly growing pack of ravenous, fearsome friends.