Steve Backshall, British adventurer and naturalist, embarks on a journey to explore the Baliem River. Located in the island of New Guinea, which is north of Australia, Steve's goal is to find out more about the hidden secrets that lay along one of the world's wildest rivers. However, travelling along the entire river is not for the faint of heart, and this journey has never been completed before. Steve begins at the source, Lake Habema, and must tackle some extreme white water rapids. During his incredible adventure, he also discovers unexplored caves, unusual animals, and meets some incredible people.