The Leper King is dead. His sister, Countess Sibylla, longs to return to the convent and leave the crown in the hands of her young son. But when the boy suddenly dies, the Order of Sion forces Sibylla to become queen and crown her estranged husband, Guion de Lusignan as king. Meanwhile, a squire named Ernoul discovers that a woman attending his sick mother in the Hospital of Saint-John is the beloved saint, Mary Magdalen, and that he is the illegitimate son of a powerful lord. As the Order of Sion regains strength and the kingdom moves ever closer to war with Salehdin, Mary seeks out the hiding place of the lost Cup of Christ... but is it the end of a long quest or a trap set by the enemy to destroy her?