Deep beneath the Nullarbor Plain, one of Australia's most hostile and barren landscapes, lies an ancient cave that has remained untouched for hundreds of thousands of years. Littering the floor of this prehistoric grave site are the perfectly preserved remains of long extinct megafauna, including previously unknown kangaroo species and the first complete skeleton of the largest carnivorous marsupial ever found - Thylacoleo carnifex. NOVA joins the first descent into the dark depths of this newly discovered cave and follows the detailed detective work on the recovered skeletons that will help piece together the past of these fascinating creatures.

Tuesday, 3/25/08 from 8-9 p.m. ET