The likeable and carefree Grand Duke of Abacco is in dire straits. There is no money left to service the State's debt; the main creditor is looking forward to expropriating the entire Duchy. The marriage with Olga, Grand Duchess of Russia, would solve everything, but a crucial letter of hers about the engagement has been stolen. Besides, a bunch of revolutionaries and a dubious businessman have other plans regarding the Grand Duke. With the intrusion of adventurer Philipp Collins into the Grand Duke's affairs, a series of frantic chases, plots and counter-plots begins.