A million years before the emergence of humans, an alien spaceship splashes into the Pacific Ocean. After it comes to rest miles underwater, a creature emerges from the vessel and, after assessing its aqueous environment, drastically alters its appearance in order to survive.
After many millennia of existence in the form of various deep-sea creatures — sharks, whales, porpoises, schools of fish — the changeling eventually leaves the safety of the water and enters the world of man. Adopting various human personas — graduate student, soldier, surfer, circus dwarf, prostitute — the ever-inquisitive changeling slowly masters the intricacies of human society.
When a strange artifact is discovered seven miles below the surface of the Pacific in the early 21st century, the changeling is inexplicably drawn to it. But so is something else: another, much older, shape-shifting alien. This chameleon’s motives for wanting to unlock the secrets of the artifact, however, are far different from the changeling’s.