The season four finale episode is a two-hour look into one of the most challenging expeditions of Jeremy Wade's life. He'll travel to the isolated and untouched jungles of Guyana, South America, where early explorers wrote about a river system filled with mysterious giants. Armed with only old journals and his rod, Wade embarks on an epic journey where he'll tackle the Essequibo — South America's third largest and least known river. He immerses himself in the culture of the Macushi Indians and must earn the trust of these native people in order to gather their knowledge and hear their stories. Once again he'll set out to separate fact from fiction. Are there terrifying ancient monsters still alive in this region's hostile waters?