Communications with the surface cut off, besieged by sand-crawling, piranha-like predators, the CalEx subsurface strike team finds itself in deep combat from the moment they step out of the hatch with no immediate prospect of return to the Upworld they left behind. Stef, Samples, Dix, and their half-breed Underworld guide, Kartkas, must find their way in this strange, hostile new environment while still trying to achieve their mission directive to recover the rare mineral discovered by Dr. Correll. If they can survive long enough to do it.