Secretly a spy but thought by his family to be a dull salesman, Harry Tasker (Arnold Schwarzenegger) is tracking down nuclear missiles in the possession of Islamic jihadist Aziz (Art Malik). Harry’s mission is complicated when he realizes his neglected wife, Helen (Jamie Lee Curtis), is contemplating an affair with Simon (Bill Paxton), a used-car salesman who claims he’s a spy. When Aziz kidnaps Harry and Helen, the secret agent must save the world and patch up his marriage at the same time.
Based on the popular board game, this comedy begins at a dinner party hosted by Mr. Boddy (Lee Ving), where 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 Col. Mustard (Martin Mull). When Boddy turns up murdered, all are suspects, and together they try to figure out who is the killer.