Prince Leo (Marcello Mastroianni), last in the line of rulers of a long-deposed monarchy on continental Europe and jaded with the frenetic search for kicks with the European jet-set, returns to his father's London town house for rest. With him are social-climber Margaret (Billie Whitelaw), to whom he is engaged, and Laszlo (Vladek Sheybal), who is planning a counter revolution ...