Mike Whittle is a 25-year-old cab driver barely surviving in a modern city. After catching his girlfriend with his wealthy uncle, he drives off in despair and stumbles into a dark cave. When he emerges, he's no longer in his own time.
He has entered a prehistoric rainforest ruled by a matriarchal clan. The tribe lives by hunting and fire-drilling, and they see Mike's taxi as a monster. But when Mike flicks a simple lighter and summons fire in the rain, they begin to worship him.
Mike realizes the cave only works with his old taxi. He starts moving between worlds—bringing burgers, medicine, seeds, and tools to the tribe, and hauling raw gold back to the modern world. With the help of his sales manager, Selena Hartman, he builds a gold empire.
But as his wealth grows, so do the dangers. His uncle Robert begins investigating the impossible source of Mike's gold. His ex-girlfriend Rachel becomes obsessed with winning him back. And the woman he now loves—Sera, the clan chief—nearly dies from a poisoned dart.
To save her, Mike uses modern medicine and burns through his fortune. Robert gets closer. The secret of the cave is nearly exposed. In the end, Mike must choose between the modern empire he built and the world where he truly belongs.
