In an impoverished suburb of Lima, in an ancient cemetery crammed with more than 1,000 pre-Columbian mummies, Peruvian archaeologist Guillermo Cock makes a startling find. He discovers dozens of corpses that differ from all the rest: they were hastily buried and disfigured by appalling wounds and fractures inflicted by steel blades and crude bullets. Forensic experts diagnose these remains as victims of a little-known battle that pitted club-wielding Inca warriors against Spanish cavalry. The battle turns out to be a decisive turning point that helps explain a long-standing mystery about the Spanish conquest of Peru. How, in 1532, did a tiny band of Spanish soldiers crush the mighty Inca empire, then the most powerful civilization in the Americas, with a network of roads that spanned over 2,000 miles? Were the conquistadors' obvious advantages -- steel arms, gunpowder and horses -- the key to their success, as is usually supposed? Or were disease and civil war more decisive factors that were downplayed by the Spanish chroniclers? With the help of this new evidence from the Lima cemetery, NOVA reveals the untold final chapter of the conquest: not the Spanish walkover familiar from popular accounts, but rather a protracted and complex war of astonishing brutality that almost led to the Spanish losing their precarious foothold in the Andes.