A noble bankrupt Frenchman lands in America to make his fortune. Looking for a job that he doesn't find, ready to do anything to earn a living, Jules de Barton reluctantly decides to accept the strange offer from the mysterious Doctor Nicholson: with no explanation the earl must enter into a marriage of convenience with a rich heiress from whom he will have to strip her of her precious blue diamond in exchange for an undreamed-of sum… A sort of prince of crooks, the enigmatic Nicholson from this Danish detective story seems to be inspired by the worrying Dr. Nikola from the bestseller of the same name by Australian Guy Boothby (1867-1905) published in 1895.