Raulhac, Cantal, France, September 1, 1905. In the forest surrounding his hometown, the young seminarian Bruno Reidal murders a child and then surrenders himself to the authorities.
Franck is an astrophysicist. His job is to perform laser drillings with the Lynx, an exploration rover on Mars. Assisted by his collegues, he spends the night looking for traces of organic life by examining rocks. In the morning, he will meet with his son who has been traveling around the world after staying with his mother.
