A body is found under the rubble of a chapel belonging to the "Emissaires," a discreet and non-violent religious community that had settled in Alsace over four hundred years ago. All the evidence suggests that it was an accident. However, when the investigators arrive at the scene, they discover that the autopsy was done in a rush, the church wasn’t sealed off, a valuable fresco had disappeared, and a strange rock had been placed inside the victim’s mouth. Is this a crime of vengeance, a settling of accounts, or a way of covering up a terrifying secret?