Isabella, the steward of Valeros in the eastern Pyrenees, has twice been falsely condemned as a heretic. In 1210, Isabella and Tomas, the mercenary she married, identified their archenemy: a secret society called Crux Lunata. At the siege of Minerve, Isabella narrowly escaped being burned with the town's heretics.

In late summer 1211, Isabella and Tomas set out to join Pedro d'Aragon's long-planned invasion of Andalusia. However, the Crux Lunata still pursue them, and Isabella flees for her life, seeking safety among the heretics hiding in caves in the hills.

The Mad Woman of La Catalane, a novella, supplements the story told in Crux Lunata, Book 3 of the Accidental Heretics adventure series, a saga of people caught in the invasion of southern France known as the Albigensian Crusade.