Josette, the daughter of a hotel-casino owner on the French Riviera is wooed by Pradier, a young gambler she (and everyone else) mistakes for the Prince of Austravia. On the other hand another young man starts courting her and she does not feel insensitive to his advances. What she does not know is that Monsieur Lefèvre, whom she feels so much to her liking, is actually the real prince of Austravia. When the Austravian revolution dethrones the prince, the young man has only one citadel left to conquer: Josette's heart.