In London, Georges Thomason (Tom Georgeson), his seductive American girlfriend Wanda Gershwitz (Jamie Lee Curtis), and their associate Ken Pile (Sir Michael Palin) are planning their latest crime: a diamond heist that should net them 13 million pounds sterling. They plan to leave the country with the goods after the heist. On Wanda's recommendation, they enlist the help of her weapons-expert brother Otto West (Kevin Kline) for this heist. Actually, Otto isn't Wanda's brother, but her latest lover, a dimwit who gets off on his own body odor and believes he's an intellectual because he reads Nietzsche and does not tolerate being called stupid by anyone. Wanda has one weakness in men which is how Otto was able to get her to be his lover: speaking Italian in seduction. Wanda and Otto plan to double-cross Georges by having him arrested for the heist while they abscond with the jewels. Wanda further plans to triple-cross Otto by eliminating him from the picture after she has the jewels. They are able to get Georges arrested with him not knowing who tipped the off the police, and implicated by elderly eyewitness Eileen Coady (Patricia Hayes). With Georges in jail, Wanda and Otto discover that he has protected his investment by moving the jewels from their agreed location to a hidden one, telling nobody where they are but offering Ken a slight hint. Georges gives Ken, an animal lover with an extreme stutter, the task of killing Mrs. Coady before she is able to testify against him, as she is the Crown's primary witness. Meanwhile, Wanda has her own plan to reach her end goal: seduce George's defense lawyer Archie Leach (John Cleese) and find out Georges' secrets about the heist, including the location of the jewels. Archie may be easy prey for Wanda's seduction, as his wife Wendy (Maria Aitken) is a self-absorbed woman who pays him little attention. Otto might throw a wrench into Wanda's plans if he finds out what she's doing.