Brother Francis is found dead outside the gates of his abbey. What was this novice doing outside in the middle of the night ? Paul finds in his cell a bible filled with strange annotations and a diagram that evokes the Tear of Saint Louis, the legendary lost diamond. Would the younger brother have found the relic and killed it to get it back ? Or is his murder linked to his strange past, as Leah seems to think ?

Lea cannot believe that a gendarme may be at the origin of threatening emails. For her, the brigade is like family. However, she must face the facts: the killer is among them. The paranoia that reigns in the team therefore does not help the investigation to move forward. But alas, time is short.