Dr M. Sanjayan travels into the Amazon’s “Intangible Zone” with a team of scientists who believe it could be the most bio-diverse place on earth. Despite being virtually “off the map”, there are still people here: Waorani, who are fierce defenders of the forest against outsiders. They help the scientists reveal the forest’s deepest scientific secrets. But seeing how people live here without destroying the forest leads Sanjayan to a startling discovery by archaeologists. The Amazon was once home to vast civilizations, and not only that, but those people once made the forest more productive, not less so. And that can still be the case today.