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.

When they save a guy called Paul Sarone from a sinking boat, he offers to help in their search for the tribe.

The mysterious Sarone is actually a snake-hunter looking for legendary anaconda snake, and when Cale is bitten by some tropical insect, Sarone takes over the boat.