The ancient world, which has already become familiar to Semyon Vasiliev, begins to change rapidly: snowfalls, snowstorms, hurricanes. The Mammoth people never stockpiled food or built warm dwellings. In the new conditions, they are doomed to destruction if they do not change centuries-old traditions. Not only does Semyon have to help his tribe out of trouble, but he has a long journey ahead of him. He has almost no hope of saving the woman he loves - only to take revenge on her kidnappers, the creators of a global environmental disaster...