The 350th Anniversary Year

It is 1998 and R-------- is about to celebrate the 350th anniversary of its liberation from Ottoman rule. The Regent, Archduke Michael, who rules on behalf of the orphaned boy-king Alexander, wants to discover if rumours about the young king’s ancestry are correct. 

Is the child descended from a man who substituted for the dissolute King Casimir II at his coronation and marriage to Queen Catharine in the early 1890s, and was he the father of her son Otto III?

The only surviving descendent of Lord Rupert is his great-granddaughter Dr Anne Gore-Ross, a freelance historian. A letter to her great-aunt Lady Helen Wingfield requests her DNA to prove/disprove the rumours and offers an all-expenses paid holiday in R--------. 

Her short stay becomes extended as she solves the mystery but with unexpected consequences for her and the royal family.