At a dinner party hosted by Mr Boddy (Lee Ving), he admits to blackmailing his visitors. These guests, who have been given aliases, are Mrs Peacock (Eileen Brennan), Miss Scarlet (Lesley Ann Warren), Mr Green (Michael McKean), Professor Plum (Christopher Lloyd), Mrs White (Madeline Kahn) and Colonel Mustard (Martin Mull). When Boddy turns up murdered, all are suspects, and together they try to figure out who is the killer.