Examines the enigmas presented by the prehistoric remains found in Chaco Canyon in New Mexico. Tells that between 850 and 1150 AD, the Chacoan people constructed massive ceremonial buildings in a complex celestial pattern throughout a vast desert region, and uses aerial and time lapse footage and computer modeling to show how the Chacoan culture designed, oriented and located these buildings in relation to the sun and moon. Pueblo Indians, descendants of the Chacoan people, also speak of the significance of Chaco to the Pueblo world today.