After baby chimpanzee Sam Simian's mother got killed by a leopard he is adopted by Liz Day the primatologist who happened to be studying Sam's chimpanzee clan. Liz decides to try and raise Sam no differently than a human baby and begins to teach Sam American Sign Language only the version she teaches him was developed by KOKO the gorilla who modified ASL for a creature with non-opposable thumbs. Sam becomes fluent in sign language and eventually shows a penchant for painting abstracts pictures eventually winning a prestigious art contest. But in Sam's new keeper's twilight years the money runs out and they are desperate so Liz and Sam travel back to the Congo where a group of researchers invited the pair to live if Sam will agree to enter the jungle and teach wild chimpanzees sign language.