A film crew headed by anthropologist Steve Cale and director Terri Flores journey through a river to find a mysterious Indian tribe and shoot a documentary on them. They save a guy called Paul Sarone from a sinking boat. He offers to help in their search for the tribe, but he is actually a snake-hunter looking for a legendary anaconda snake, and when Cale is bitten by a tropical insect, Sarone takes over the boat.