A resourceful jungle boy sets out to reach Sobrinini beyond a colossal waterfall in hopes of learning about his parents. Traveling with animal companions and an aged naturalist, he confronts snakes, jaguars, alligators, headhunters, and treacherous rapids. He endures ambushes, captivity, and fierce struggles, uses cunning and physical skill to escape predators and enemies, explores snake-infested isles, and survives a mad stampede and swirling cataract waters. Encounters deepen a mystery about his origins while episodes of rescue, loyalty, and relentless survival drive the fast-paced adventure.