On the walls of their caves, 17,000 years ago, the men of Cro-Magnon traced the first history of the sky and its stars. If Lascaux, the prehistoric Sistine Chapel, was first and foremost a temple dedicated to the celestial constellations. Crazy? Yet this is the demonstration that Chantal Jègues-Wolkiewiez, an ethnologist and astronomer, attempts. Between a police investigation and an astronomical tale, this film plunges us into the mists of time.