In June 2019, Étienne Davodeau embarked on a remarkable 800-kilometer journey, traveling on foot with only a backpack, from the Pech Merle cave to Bure. This journey contrasts the ancient cave paintings—still preserved as humanity's treasures—with the grim reality of nuclear waste buried underground, posing a dire threat to all living species. As a sapiens among sapiens, Davodeau examines our relationship with the earth beneath our feet. Acting as a walker-observer, he raises the alarm about an impending collective crisis, inviting us on an evocative journey through time and space. What kind of planet will future generations inherit? How can we warn them about this very real and grave danger to their survival?