The millionaire businessman Prévailles has just married the young dancer Jenny Saphir, whose career he has pushed. A few years earlier, Jenny had fallen madly in love with Lupin. Lupin, aware of Prévailles' activities, disguises himself to warn Jenny of the danger she's in, and to protect her. For she possesses the sapphire of Genghis Khan, a priceless jewel with a legendary curse, a gift from General Ignatieff, one of the dancer's previous admirers.
