When his clan and family are massacred, Ao, a desperate Neanderthal man, decides to leave the North Country and head south to his birthplace. His quest is to join his twin brother, from whom he was separated when he was nine. On his long and treacherous journey, he meets Aki, a Homo Sapien woman. Together they must battle terrifying animals and treacherous landscapes in order to survive. The biggest danger, however, are the "Hyena-Men", a clan of Homo Sapiens that are out to kill him and his species.