Adventurer and naturalist Steve Backshall sets out to explore one of the wildest rivers in the world, the mighty Baliem River in the island of New Guinea, just north of Australia. He is on a mission to discover the ancient tribes that live along its banks, explore unknown caves and meet the dangerous animals lurking in the river and surrounding jungle. But the only way to discover these hidden worlds is to travel the river from source to sea - a feat that has never been achieved before.
In this second episode, Steve and his crew kayak Baliem's lower gorge, one of the most extreme stretches of white water on the planet. With jagged rock walls looming overhead and crashing currents bearing down on the kayaks, the risk of capsizing is constant. Battling wild weather and dense jungle, Steve's explorations of the surrounding valley prove equally as challenging. Steve encounters large spiders, fierce wasp nests and a local tribe who have little contact with the outside world.
Finally entering the tidal reaches of the Baliem River, Steve has to reconcile his passionate belief in conservation with a local tribe's determination to hunt crocodiles in the region.