NOVA and National Geographic present exclusive access to a unique discovery of ancient remains. Located in an almost inaccessible chamber deep in a South African cave, the site required recruiting a special team of experts slender enough to wriggle down a vertical, pitch-dark, eight inch-wide passage. Most fossil discoveries of human relatives consist of just a handful of bones. But down in this hidden chamber, the team uncovered an unprecedented trove – so far, over 1,500 bones – with the potential to rewrite the story of our origins. They may help fill in a crucial gap in the fossil record and tell us how Homo, the first member of the human family, emerged from ape-like ancestors like the famous Lucy. But how did hundreds of bones end up in the remote chamber? The experts are considering every mind-boggling possibility. Join NOVA on the treacherous descent into this cave of spectacular and enigmatic finds, and discover their startling implications for the saga of what made us human.