Léo is the two-year old, son of the acting manager of a factory on the brink of closing. When employees discover the news, Bruno, a more radical Worker who is willing to fight for his job, abducts Léo.

Five gigantic sinkholes have recently been discovered on a remote plateau on the other side of the world. A team of experts has made the trip to descend into the depths. Among them is professor Georges Lebrun, who has come with his wife.