Camouflage

Joe Haldeman's 2005 Nebula Award winning Camouflage is the story of two aliens living on Earth.

2019: An artifact has been found in one of the trenches on the ocean floor. It was under ancient coral that was at least a million years old. A team of scientists raises the artifact - a oblong sphere of some reflective metal, heavier than any known on the periodic table.

1931: The changeling is from a planet that is so extreme that its kind has learned to evolve to live in any conditions. Now on Earth, it has lived in the sea for longer than it can remember. It formed itself into various sea creatures and learned to live among them. Now it will attempt to learn about the strange creatures who live on land. It has seen sailors and fisherman but doesn't understand their complexity. Once forming its shape into a human, it will have to learn language and social skills along with the everyday functions we take for granted.

Pre-Christian Era: The chameleon has lived on Earth for as long as it can remember. It is in the form of a human male. It can change its appearance, but can only be a human male. Living through every period of human evolution, its base instinct is always survival. Since it cannot die, it feels it is superior to humans.

The artifact lifted from the ocean will likely draw the attention of both aliens. One who has always been attracted to the Pacific Ocean and one who wants a greater challenge than killing humans. Each who has looked for another like itself.

Haldeman, Joe. (2004). Camouflage. New York: Penguin.