Bill's son is kidnapped by an Amazon tribe. Bill tried to pursue but lost them in the jungle. Over a decade later, he tries to arrange an expedition to find his son. The results are a disaster. His partner is eaten by cannibals and he flees only to find his son as one of the natives trying to kill him.
Tommy, now a young man, recognizes his father and helps him escape. Tommy takes him to friendly natives who care for Bill. Bill learns of how completely Tommy has transformed into a tribal man speaking their language as if it was native and as if his father's language was foreign. Then the tribe drugs Bill and takes him back to civilization. Bill wakes up with no clue where his son is.
A deadly conflict arises between some of the natives and the ones who ate Bill's partner try to kill Tommy's adopted family. Tommy goes on a quest into the city even though he's a tribesman. He finds his dad and the two of them rescue Tommy's adopted family. Bill helps the tribe further as Tommy returns to the jungle to live.
The Emerald Forest contains examples of:
- The Amazon: Set where the city clashes with the jungle.
- Brazil: An unknown city, near the Rainforest. Shot in the states of Pará, Rio de Janeiro and São Paulo.
- Cannibal Tribe: The Fierce People.
- Conlang: The movie has a fictional tribe, culture and language, based on other Amazon cultures, and on Mayincatec.
- Den of Iniquity: The bar-brothel. Such a bad place that the Big Bad and The Dragon teach the Cannibal Tribe how to shoot guns there.
- Going Native: Tommy was raised as a native, but even when he had the chance to return to the city and modern world, he remained a native. Actually, he even becomes the savior and lawful chief of the tribe, first by finding the Sacred stones, then saving the women.
- Green Aesop: Native people "still know what we have forgotten", as said by the Closing Credits. The deforestation is bad :Invisible man: They are taking the skin off The World. How will it breathe ?
- I'm a Humanitarian: The Fierce People eat their enemies.
- In Harmony with Nature: The Invisible People, as a Foil to the "modern" people.
- Language Barrier: Downplayed, since both Bill and Tommy understand a little of each other's language. They still have very different native tongues.
- Mayincatec: Set in modern Latin America, but still valid with the priests, ceremonial paintings, magic chaman with a drug culture, cannibalism, Sacred stones and the usual jungle with its classic wildlife.
- Raised by Natives: The American boy Tommy is raised by an Amazonian tribe.
- Sex Slave: The Evil Mooks use the Cannibal Tribe to kidnap young Amazonian women, who are Made a Slave for this purpose. The climax is about freeing them from their Den of Iniquity.