When a corpse clutching a crystal chess piece is found in the old fortress of Bitche, in the Lorraine region, police lieutenant Nicolas Muller is sent to investigate. He is accompanied by a young female intern and soon discovers, during this complex investigation, that he is actually related to her. While the Lorraine is familiar ground to Muller, being his birthplace, his investigation is made difficult by the fact that all the clues point to a crystal factory managed by his own father and sister - a family legacy he turned his back on by becoming a policeman. The number of victims soon grows, as does the list of suspects, among which are his own family members.