Steve and Justine are camped at the bottom of an enormous hole lying deep in the jungle. They are the first naturalists ever to explore this bizarre twilight world and they stumble across a network of caverns and passages, never explored by humans before. Meanwhile, Tara and her team face the white water rapids of a remote jungle river in order to be the first team of biologists ever to explore the pristine jungle that lies upstream.

• Steve Backshall
• Alisdair Simpson
• George McGavin