Publisher's Summary from audible.com
Sent on an impossible mission by Kingfountain's ruler into the heart of the enemy's capital as two mighty kingdoms prepare for war, Ankarette Tryneowy must divine the location of a magical sword, perhaps their key to victory. What she finds is the truth - one she could never have foreseen.
Searching for Firebos, the sword of ancient kings, is no simple task. It disappeared after one of the most powerful Fountain-blessed figures, the Maid of Donremy, used it in battle, and no one - except perhaps the Maid's dearest friend, the Duke of La Marche - knows its whereabouts. But when Ankarette finds the aging duke in his prison cell and hears the mystery he unveils, her mission becomes more perilous than she could have possibly imagined.