Murders in Lorraine

A burned corpse of a woman is discovered inside the Bitche citadel, in Lorraine, carrying a crystal chess piece. Lieutenant Nicolas Muller investigates with his gendarme warrant officer Patrick Joly and a new recruit intern Lola Paoli. This crystal factory belongs to his father Herve Muller. The victim is identified as a factory worker. Soon two other factory workers are killed on a broken neck. Muller learns from his younger sister Florence Muller that in order to prevent the crystal factory's bankruptcy, she intentionally set fire to the factory with the purpose of collecting insurance money, but unaware of the first victim inside. Further, Muller finds out that Patrick Joly is the killer of the second and the third victim. As the first victim's boyfriend, he took revenge on them since they are the fire-setting helper of Florence Muller.