You won't believe it, but it really happened! Vasya Matveyshchikov woke up in the Stone Age, thirty thousand years BC! But he could have been scared when a spatial window suddenly appeared in front of him. And then none of this would have happened. He wouldn’t have to run away from the Forest People, fight a cave bear, mammoths and saber-toothed tigers, or save the Reed Cat tribe from imminent death. All this is terribly interesting, but Vasya needs to return home. And for this you need to do the almost impossible - to reveal the secret of the Spirit of Fire...