Christine Boskoff is one of the world's best female climbers, and one of only three to have climbed the seven summits. Charlie Fowler is a Coloradan who is known as one of the world's best first ascensionists. Together, they set out on a two-month trip to climb some remote mountains in western China. When they didn't return in early December, friends became worried and started searching, but so far, there's no sign of them. The site www.alpinist.com has been doing some detective work, and dissects what is known right now about the missing duo.