Belle is afraid to go home to England where her cousin George will force her to marry him. She exchanges identity with her friend and is on her way to Vienna to be a governess when the coach is attacked, and her companions killed. She is saved by Count Rupert's arrival, and taken by him to his castle where, he tells her, she can be a companion to his niece Gisela.
There are some odd people at the castle - the Count's mistress Anna who resents Belle's advent, and is dismissed; the dim-witted Johann who wants Gisela, and the dangerous Uncle Otto, who is anxious to gain control of Gisela's fortune. Outside are other men Belle needs to avoid. Then Gisela is sent away to meet a prospective husband, and Count Rupert persuades Belle to help him in Vienna, where he hopes to persuade the politicians to return the Tyrol to Austria.
Belle meets many people, especially Lord Castlereagh, and aids the Count to arrange secret meetings. Then she discovers that Gisela is staying at a convent outside Vienna, where she has become friendly with another girl whose brother is in Vienna. Soon Belle becomes worried as both George and Otto arrive, and to escape George Belle agrees to marry a minor English diplomat. The Count pursues them and takes Belle back to Vienna. Otta and Anna contrive to capture Belle, but Rupert rescues her. Then news of Napoleon's escape from Elba reaches Vienna.