Tharg of the Bison Clan, young and strong, is out hunting. Having killed a stag without a weapon, by breaking its neck, he is resting on the dead animal when he is attacked by Dwifa of the Beaver Clan. Avoiding Dwifa's spear, Tharg chases him, managing to wound him with a stone when Dwifa escapes across a river. Returning for his stag, Tharg finds it stolen, and tracks it to the camp of a tribe of strangers, the Clan of the Wolf. The thief was the giant Matalfa, and the matter will be settled by a battle three days hence. Tharg manages to defeat Matalfa, but spares his life. Shortly after, Dwifa puts a curse on Tharg, and Tharg and his tribe members are afraid. When Tharg goes to attack Dwifa's cave, his father and grandfather are both slain, and everyone believes in Dwifa's magic.
Tharg is banished from his tribe, and his young wife Vaia goes with him. His spirit is declining, until they are attacked by Matalfa, who has followed them. Tharg slays him and regains his spirit, until the couple are captured and enslaved by a more powerful tribe. Tharg and Vaia are protected by the Priest Vraka, who appreciates Tharg's great strength, and the power of Vaia's love over him. After two years of slavery, dedicated to the building of a Stonehenge-like temple site, Tharg and Vaia save Vraka's life, and he becomes king.
Vraka grants Tharg his wish to be freed from Dwifa's spell, which he believes still holds him, and the couple returns to the Clan of the Bison with their baby son, to find that Dwifa's tribe has them virtually enslaved. Tharg trains his clan in the use of the bow and arrow, which he'd learned from Vraks's tribe, and they defeat the Beavers. Dwifa manages to commit suicide before being tortured, and Tharg becomes the chief of the Bisons.