Prince Alexis of Granovia is traveling incognito under the name of H. Leslie. On his travels he meets Cecile Dubois, with whom he falls desperately in love. At the time she feels sure he is about to propose to her. He is suddenly recalled to his own country on account of the state of his father's health. He writes to Cecile telling her who he really is and that he is going away, never to return. Cecile does not propose to be cast off in this manner and gets her sister, Helene, who owns a hotel in the mountains, to let her come to see her. There she writes to the prince, asking for a last interview before he goes away. He goes to the hotel, which is an old converted castle. The sisters realize that they have a good opportunity to levy blackmail on the prince so they lure him to one of the old dungeons and lock him up to stay till he signs a paper agreeing to marry Cecile. The disappearance of the prince causes an awful furor and Nick Winter, the great detective, is called in to solve the mystery. He gets a clue and suspects that the sisters have some knowledge of the whereabouts of the prince. He has them watched and when he is sure of his ground he disguises himself as the father of the prince and comes to the hotel to stay. The sisters decide to risk everything on one great coup so they drug the people who they think are the court of Granovia. As they are searching through the effects of their guests Nick comes to. He has been pretending all the time. Caught red-handed the sisters are in a predicament, and are forced to release the prince. The girls are lured to the kingdom of Granovia and are there cast into prison. The prince, however, remembering his former attachment for Cecile, arranges for their escape. He delegates Nick to get them out. Nick succeeds by employing his utmost ingenuity.