While the body of a man is spat out by the waters of a torrent, a young teenager without an identity takes refuge in Alex's chalet. Mute, frightened, she seems to discover the world and technology for the first time. Did she manage to escape from a long sequestration, or did she live apart from everyone, somewhere in the mountains? In any case, the danger lurks: a "shadow" seems determined to recover it. Alex takes her under his wing and embarks on a double investigation. A search for truth that will plunge him into the heart of the sometimes disturbing universe of survivalists.