The book is a sequel—with a fully independent plot—to the well-known novella by the same author, “The Fight for Fire.” It describes a full of adventures journey of two prehistoric people of the Stone Age—young men Una and Zura—who set out to scout new hunting grounds for their tribe. On the way, they take part in a battle against the saber-toothed tiger Machairod and a giant python; they meet the Forest People, befriend them, and save them from the warlike and bloodthirsty tribe of the Fire People. And finally, they tame a giant cave lion, who in turn repeatedly comes to their aid.