Leaving his home in the hidden valley, young Toca must journey for a sun season to and from the endless water in order to prove his manhood. He must accomplish the tribe's Katata Ado if he is ever to become chief. Before leaving, old Chief Acuta secretly gives Toca - whose spirit image and talisman is the Black Ghost - instructions for him to bring back three vital things. If he fails, the old chief has foreseen, over the past generations, that their people, the Nashua, will cease to exist.

Early in Toca's journey through the dense rain forest of the Amazon, he encounters a young girl his age, named Shana, and her father who are not from the Amazon and are lost. They desperately need help to survive in this deadly environment. Shortly after finding them, Shana's father dies, leaving her in the hands of this strange Amazon Indian. The Black Ghost now has another heavy burden caring for this girl as he must continue and finish his strenuous Katata Ado before the 13th full moon rises, or all is lost for him and his people. The young ones face many surprising and life-threatening situations throughout the long and tiring journey naturally causing them to grow close and mature, becoming adults.

Nearing the end as they are getting close to the hidden valley, the two struggle to make it as they encounter a giant obstacle that could change the course of everything.