New York City native Mary Esther Lee (1837-1914) married the prince brother of the Queen of Denmark in 1874 and was made a member of the royal family after his death. An active philanthropist to Protestant causes, Princess Mary von Waldersee then wed a German count whose close ties to the Prussian court made her an intimate friend of Kaiser Wilhelm II and a mentor to his young wife. Mary's influence caused many to believe she was the power behind the throne, although she preferred to remain in the background. This biography chronicles the remarkable life of an American woman of modest wealth who rose to power in Europe's royal courts.