Mars, 2176 AD. Long colonized by human settlers, the Red Planet has become the manifest destiny of an over-populated Earth. 640,000 people now live and work at far-flung outposts all over Mars, mining the planet for its abundant natural resources. But one of those mining operations has uncovered a deadly mother lode: a long-dormant Martian civilization whose warriors, now unleashed and apparently unstoppable, are systematically taking over the bodies of human intruders, bent on ridding the planet of the invaders from Earth.