In this episode, England sends more men to Brittany, de Blois tries to prevent them, and that friggin' guy, Robert of Artois, eats a crossbow bolt.
Map of Brittany.
Here is the reference to the bit I read at the end (translation is mine): Druon, Maurice, Les rois maudits VI: Le lis et le lion, 1970, Le Livre de Poche, pages 305-310.