An accident occurred while testing a new device for studying rock layers. Semyon Vasiliev could only envy his comrades: they died immediately, and he found himself abandoned tens of thousands of years ago - in the periglacial steppe, where mammoths, rhinoceroses and saber-toothed tigers roam. Where two races came together in mortal combat, which descendants will call Neanderthals and Cro-Magnons. Semyon is no stranger to the taiga and tundra - he is a geologist with many years of experience, but now he has nothing except an old pocket knife and a love of life. He will learn to kill mammoths and win battles with troglodytes, but this is not enough to become a full-fledged male warrior of a primitive tribe. It is necessary to pass the main test: to die and be born again...