The excavation of 81 skeletons at Cerro Cerrillos provided the occasion for a rigorously scientific deconstruction of human sacrifice, its changing methods and its social meaning among the Muchik peoples of ancient Peru. This paper shows how bioarchaeology and field investigation together can rediscover the root and purpose of this disturbingly prevalent prehistoric practice. Be warned: the authors' clinical and unexpurgated accounts of Andean responses to the spirit world are not for the fainthearted.