The young French scholar, Catherine LeVendeur, is rather pleased to see off her estranged younger sister, Agnes, through marriage to a German lord. Bitter about their religious differences, Agnes wants nothing to do with Catherine and happily sets off with her sizeable dowry and two knights in escort.But soon one of the escorts returns with terrible news: Agnes' new husband appears to have been murdered, and Agnes is the prime suspect - accused of murder by poisoning, or worse, witchcraft.In spite of their differences, Catherine believes in Agnes' innocence, and pledges to do everything she can to save her sister. But when Catherine and her family travel to Germany to begin investigating, amongst a dangerously volatile religious climate, it becomes clear that their long-dreamt-of peaceful life remains in the distant future - if they live to see it.