With his family, research assistants and pet seal in tow, an anthropologist sets sail for the South Pacific, hoping to find uncharted territory. But a shipwreck strands them on a treacherous island inhabited by mutant beasts. Braving saber-toothed wolves, carnivorous ostriches and the threat of an active volcano, the visitors eventually discover the island's one human inhabitant: a native boy left behind by his tribe as a test of his manhood.