Father Cyril Nouvel has mysteriously disappeared. Yet it is at his initiative that his brother, Gendarme Louis Nouvel, and his mentor, Abbé Gomis, find themselves gathered at the site of an abandoned old fort. As they set out to search for him in this vast and oppressive place, tension rises between the two men. Even if they cannot admit it to themselves, each knows deep down that he holds a part of the truth.