S1, E3: In the 1990s, a high Himalayan cave in Upper Mustang, Nepal, was discovered that contained 42 ancient people, buried on wooden bunk beds. American archaeologist, Dr. Mark Aldenderfer, believes there must be more burial caves but the challenge is how to find them, deep within cliff faces in the cold and inhospitable environment of the Himalaya. He needs the world's best technical climbers to do the searching.