In twelfth century Languedoc a subversive heresy of Eastern origin flourished to an extraordinary degree. The Albingenses believed that the world was created by an evil spirit, and that all worldly things - including the Church - were by nature sinful.

Jonathan Sumption’s acclaimed history examines the roots of the heresy, the uniquely rich culture of the region which nurtured it, and the crusade launched against it by the Church which resulted in one of the most savage of all medieval wars.