London gangster George Thomason and his right-hand man, Ken Pile, an animal lover with a stutter, plan a jewel heist. They bring in two Americans: con artist Wanda Gershwitz and weapons expert Otto West, a mean-spirited Anglophobe. Wanda and Otto are lovers, but they hide this from George and Ken, pretending to be siblings, so Wanda can work her charms on them. The heist is successful, and the gang escapes with a large sum in diamonds that they hide in a safe in an old workshop. Soon after, Wanda and Otto betray George to the police, and he is arrested. They return to collect the diamonds, with Wanda planning to double-cross Otto as well, but find that George has moved them. In Ken's fish tank, Wanda discovers the key to the safe deposit box containing the diamonds and hides it in her pendant. Wanda decides to seduce George's barrister, Archie Leach, so he can persuade George to plead guilty and give up the location of the diamonds. Archie is in a loveless marriage and falls for Wanda; Otto is jealous, and his interference causes Wanda and Archie's liaisons to go disastrously wrong. Wanda accidentally leaves her pendant at Archie's house, and Archie's wife, Wendy, mistakes it as a gift for her. At Wanda's insistence, Archie recovers the pendant by staging a burglary. Eventually, Archie, feeling guilty, ends the affair. George asks Ken to kill Mrs Coady, the
Crown's only eyewitness. To his dismay, Ken accidentally kills her three dogs by means of a series of staged accidents, but ultimately succeeds in his aim when she dies of a heart attack. Wanda and Otto want George to remain in jail, but with no witness, he seems set to get off. At his trial, defence witness Wanda unexpectedly gives evidence against him. When Archie, stunned, flubs his
cross-examination and calls her "darling", Wendy realises that Archie has had an affair and decides to divorce him. Otto tries to force Ken to reveal the location of the diamonds by eating his pet fish, leaving Ken's favourite, named Wanda, until last. Ken reveals that the diamonds are at a hotel near
Heathrow Airport. With his career and marriage over, Archie resolves to cut his losses, steal the loot, and flee to South America. Promised less jail time, George tells Archie that Ken knows where the diamonds are. Archie sees Wanda fleeing the courthouse, pulls her into his car, and races to Ken's flat. As Archie runs into the building, Otto steals his car, taking Wanda with him. Ken and Archie give chase. Otto and Wanda recover the diamonds, but Wanda double-crosses him and leaves him unconscious in a broom cupboard. Recovering, Otto shoots his way out of the cupboard and is confronted by Archie. Otto is about to kill him, but Archie stalls him by taunting Otto about American failures such as the
Vietnam War. Ken arrives driving a steamroller, seeking vengeance for the fish; Otto, who has stepped in wet concrete and cannot move, is run over but survives. Archie and Wanda board the plane, and Otto, clinging to the window outside, curses them until he is blown off during takeoff. ==Cast==