 A strait-laced British banker hires a strange private detective (Topol) to follow his free-spirited American wife (Farrow), whom he suspects is cheating on him. The wife becomes aware of the detective following her, and leads him through London in a sort of a game. Soon this attention from the detective is providing her with the love and fun she is lacking from her British husband. The detective explains to the husband that his wife is not cheating on him, but just needs more affection and fun in her life, and challenges him to provide her with this.