Deep in the heart of the Amazon rainforest, shrouded in thick clouds and virtually undetectable from the air, is an undiscovered world: the Essequibo - one of South America’s largest rivers. Uncharted and wild, it flows a thousand miles through impassable gorges and dramatic waterfalls. Now, for the first time, a team of film-makers and scientists explore this lost and mysterious world – an adventure through impenetrable jungles and treacherous swamps with strange plants, animals and unknown Amazon tribes.