In the remote desert valley of Chaco Canyon, New Mexico stand the remains of an incredible ancient city and pilgrimage centre. Centuries before Columbus, this place was one of North America’s greatest sacred sites and the heart of a sophisticated Native American civilisation. Around 1100 AD, this mysterious community fell asunder, ravaged by climate change and drought. Archaeological evidence reveals that in their struggle for survival, some resorted to violence and murder. But there are signs of something even more shocking. Driven to desperation, some may have done more than just kill their enemies. This explores this fascinating story.