With its picturesque lakes and castles, the forest of Broceliande is the last remnant of the fairy kingdom, linked by Breton lore to the tale of King Arthur and the Round Table. It seems to be a fine destination for Commissaire Dupin and his team to take a summer field trip, but when the body of a historian turns up, Dupin is called upon to make his seventh investigation, following The Granite Coast Murders. Before too long, there are more victims. How is it related to the most recent archaeological digs in the area? And why aren't the locals willing to talk?