The towering Himalayas were among the last places on Earth humans settled. Scaling sheer cliff sides, a team of climbers and scientists hunts for clues to when the early people came to settle the forbidding landscape, where they came from, and how they adapted to survive the high altitude. The team discovers caves filled with human bones and artefacts that date from 2,800 BC to 650 AD, including gold masks and Chinese silk. Some artefacts are enigmatic, pointing to early death rituals, beliefs in zombies and vampires. Yet the most critical evidence of all is the ancient human DNA they recover from the caves. It will not only tell them about the early pioneers' origins, but it will lead to a remarkable twist in the evolutionary story of modern Himalayan peoples, proving homo sapiens mated at some time in prehistory with a now-extinct hominid called the Denisovans, an encounter that enables today's Himalayan people to thrive at high altitude. Set on vertical cliff faces, these archaeological and genetic studies are unprecedented, using cutting-edge science to unlock the secrets of our past.