In the New Mexico badlands, the skeleton of a woman is found--and the case is assigned to FBI Agent Corrie Swanson. The victim walked into the desert, shedding clothes as she went, and then died in agony of heatstroke and thirst. Two rare artifacts are found clutched in her bony hands--lightning stones used by the ancient Chaco people to summon the gods. Is it suicide or... sacrifice? Agent Swanson brings in archaeologist Nora Kelly to investigate. When a second body is found--exactly like the other--the two realize the case runs deeper than they thought. As Corrie and Nora pursue their investigation into remote canyons, haunted ruins, and long-lost rituals, they find themselves awakening a slumbering menace: a dark power brought to life once again, which threatens a malevolency beyond all understanding.