When Cunda, a man living deep in the Brazilian rainforest, is bitten by a snake, he has a hallucination of four chimpanzees. Once he recovers, he is shocked to find the four chimpanzees waiting for him at home, and, believing them to be special, decides to take them to the city in order to sell them.
According to an Amazonian legend, every month, during the full moon, a Brazilian fishing village receives a mysterious guest: the Boto, who transforms into a human to seduce and be loved by women and hated by men. One of her conquests is the daughter of a fisherman, who has a son with the Boto. He constantly reappears to seduce her, and even when she marries, he continues to look for her. This provokes the ire of the husband, who wants to kill him anyway.
For ten years, engineer Bill Markham has searched tirelessly for his son Tommy who disappeared from the edge of the Brazilian rainforest. Miraculously, he finds the boy living among the reclusive Amazon tribe who adopted him. And that's when Bill's adventure truly begins. For his son is now a grown tribesman who moves skillfully through this beautiful-but-dangerous terrain, fearful only of those who would exploit it. And as Bill attempts to "rescue" him from the savagery of the untamed jungle, Tommy challenges Bill's idea of true civilization and his notions about who needs rescuing.
