On an unlucky day 13,000 years ago, a slightly built, malnourished teenager missed her footing and tumbled to the bottom of a 100-foot pit deep inside a cave in Mexico’s Yucatan. Rising seas flooded the cave and, until recently, cut it off from the outside world. Then a team of divers chanced upon her nearly complete and astonishingly well-preserved skeleton alongside fossils of extinct Ice Age beasts such as giant sloths and saber-tooth tigers. NOVA takes you on a spectacular and risky underwater expedition to recover her bones and explores one of science’s most controversial riddles: the origins of the First Americans. Intricate detective work reveals that the young woman’s bones are among the earliest known human remains in the Americas. What drove her to venture nearly a mile underground in the vast cave? Where did her people come from, and why does she look so distinct from today’s Native Americans? From the stunning Mexico cave to the wilderness of the Yukon, from the genetics lab to the latest in forensics, NOVA pursues tantalizing new clues that are rewriting the story of the forgotten first people of the Americas.