Who would kill a Carthusian monk and why? As the investigators will find out, the key to the mystery lies in the ultra-secret formula of the Chartreuse plant liqueur.Who would kill a Carthusian monk and why? As the investigators will find out, the key to the mystery lies in the ultra-secret formula of the Chartreuse plant liqueur.Who would kill a Carthusian monk and why? As the investigators will find out, the key to the mystery lies in the ultra-secret formula of the Chartreuse plant liqueur.