At the heart of the Tassili n'Ajjer, in one of the most inaccessible regions of the Algerian Sahara, lies Sefar.A city of stone and silence, known as the City of a Thousand Caves.A place legends call cursed... and one no one has ever truly understood.For nearly a century, every expedition that has ventured too far into Sefar has met the same fate: missions abruptly cut short, incoherent testimonies, unexplained disappearances.Officially, Sefar is classified as an extreme archaeological site.Unofficially, it is a zone best avoided.In 2025, a Franco-Algerian scientific mission receives exceptional authorization to explore a canyon closed since the 1980s. Leading the expedition is Lina Aït-Taleb, a renowned archaeologist convinced that Sefar's rock paintings conceal a forgotten message.At her side: Marc Delval, a French geologist-rational, skeptical, and a specialist in ancient rock formations.Naomi Stein, a historian of religions, disturbed by strange correspondences between Saharan symbols and ancient cults.Youssef Ben Salem, a Tuareg guide and the mission's logistical coordinator.Very quickly, unease sets in.Instruments begin to fail.Voices seem to echo within the rock.At night, the desert feels alive.Then, one morning, Marc Delval disappears.No trace. No explanation. A passage with no way out.From that moment on, the mission collapses.Fear takes hold. Certainties crumble.And one question begins to haunt every member of the team: What if Sefar doesn't just hide its secrets...but makes sure no one ever leaves?