In the middle of the oyster farm park near the idyllic coastal town of Cancale, a murdered woman is found. Commissaire Julie Roche and her team set out to find the killer and stumble upon an ominous private school in the Breton hinterland. What secrets are hidden behind the high stone walls of this elite institution? And what is its charming director hiding? The investigators find a clue that takes them deep into the past. Along the way, they must realize: the murderer is already on the hunt for more victims. Will they be able to stop him?.