Two women, separated by eight centuries, become caught up in the same mystery when volunteer archaeologist Alice Tanner, working in a cave near Carcassonne, stumbles upon two skeletons, and a stone ring engraved with a labyrinth which had been entrusted to Alais, the daughter of one of the appointed guardians of the Holy Grail, in 1209 on the eve of the invasion by French Crusaders.
