A trio of English hooligans—Terry (Andrew Ellis), Nathan (Ian Kenny) and Gaz (Jake Curran)—think they've found the perfect target for a robbery—a mansion in the countryside with a safe full of cash. Nathan's girlfriend Mary (Maisie Williams) reluctantly agrees to help them. They find out from Terry's unsuspecting mother, who cleans the home for the owners, that the elderly couple will be out for the evening, leaving the safe in the basement unattended.
But when Richard Huggins (Sylvester McCoy) and his wife Ellen (Rita Tushingham) come home early, the tables are suddenly turned. As a deadly game of cat and mouse ensues, the dim-witted thieves learn that the couple are hardly as defenseless as they expected, and sinister secrets are exposed.