A violent explosion occurs in the bay of Sète. A worried mother goes looking for her son, Maxime. Her life is turned upside down when the body of woman, her own sister whom she hasn't seen in over 15 years, is found on a beach.
Chloé, Anna and Mathieu decide to go hiking, followed by Rose, who is under the spell of the handsome graphic designer. But their excursion turns into a drama when they are taken hostage by Clara, a mysterious and threatening stranger.