The Earth Corps member code-named Liquidator returns to Big Sur in search of further clues to the origin of these monsters, whereupon he discovers a race of sentient tree-beings, the "Redwoods," who explain that they are part of a race of subterranean creatures known as "Mutores," and that their kind sealed the evil "Inhumanoids" Tendril and D'Compose beneath the Earth ages ago. The malevolent Inhumanoid leader, "Metlar," remains imprisoned below the surface, paralyzed by the magnetic field of a Mutore duo named "Magnokor."