Back in Brittany, Captain Morgane Ledantec is confronted with the discovery of human bones after the fall of a sacred oak during a storm. The victim was a follower of druidism which Morgane was introduced to as a teenager by her godmother.

Pauline has her own way of doing road safety: as a trainer in a point recovery center during the day, she becomes a serial killer of drivers at night.

Emergency medicine intern Margaux can no longer stand it. During another very hectic and patient-filled shift, she forgets a homeless woman on a stretcher who then dies. Shocked Margaux has no choice but to continue working. But suddenly, her body starts sweating blood uncontrollably.