Rennes le Chateau: The Road to Sion

Icy gist Dame Jehanne d'Valois.
Here lies Joan Valois, read the inscription on a coffin under the Church of the Magdalene in Rennes le Chateau, France.  Sara Cabot, a Carcassonne detective, had just verified her great grandmother's tales that an imposter had burned at the stake for Joan of Arc and she was next in line for the French throne as Joan's descendent.

Jehanne d'Valois escaping the flames was only the beginning of long held secrets to be revealed once Cabot was coroneted as queen of France, including the ancient alien laboratory under the ruins of Perillos and the monstrosities created by the Nazis beneath Rennes le Chateau.