In our world, Semyon Vasiliev was enthusiastically engaged in geology. Only fate prepared for him a different career: to become a warrior of the Cro-Magnon tribe, a mammoth hunter. For thousands of years, a war has been going on in the periglacial steppes - two humanity cannot get along together. Some cut off their enemies' heads, others just take scalps. Trying to stop the massacre, Semyon is captured by the Neanderthals. He long ago learned to win with weapons in his hands, but he loses a duel with someone else’s faith, with a different worldview - and ends up on a bed of torture...