NOVA follows an international team of archaeologists and spelunkers into the Rio la Venta Gorge deep in the Chiapas jungle of Central America. In a rugged canyon they find caves filled with startling remains of a people called the Zoque who lived hundreds of years before the Maya. The extreme inaccessibility and relative dryness of the caves has preserved rare artifacts including bones, clothes, rope, and jewelry. Moving downstream from the caves the team finds a legendary city hidden in a tangle of jungle vines. Evidence of the Zoque's sophisticated writing system and their practice of ritualistic cannibalism and child sacrifice is shedding new light on a little known civilization.