Em 1912, o príncipe Charles (Laurence Olivier), regente de um reino na Europa, faz uma visita a Londres para participar da coroação do novo rei britânico. Ele passa a noite em um clube, onde conhece Elsie (Marilyn Monroe), uma corista americana. O regente fica encantado pela jovem e resolve chamá-la para um jantar na embaixada. A convite da rainha, Elsie fica mais tempo e começa a trazer Charles de volta à vida.
U.S. Embassy employee Lee Cochrane and his wife, Sue, receive a shock when they discover that their 18-month-old son, Simon, has disappeared in London. He was last seen with their nanny, and the couple seemingly have no leads that might help police Detective Craig in his investigation. The media sensationalizes the incident, causing an unnecessary distraction as the couple prepares to confront the culprit face-to-face.
Around the turn of the century, in England, alcoholic Uncle Willie is the bane of his family, of which his brother-in-law is the family spokesman. It is decided to let Uncle Willie buy a bicycle shop in order to impress Virginia van Stuyden, an American heiress in love with Frank. This pleases Uncle Willie's young nephew, Charles. Complications arise when stuffy lord, Sir George Probus, at whose home Virginia is staying, becomes shocked when she attends a carnival.
