Veteran climber Mark Synnott never planned on climbing Mount Everest, but a hundred-year mystery lured him into an expedition--and an awesome history of passionate adventure, chilling tragedy, and human aspiration unfolded.   On June 8, 1924, George Mallory and "Sandy" Irvine set out to stand on the roof of the world, where no one had stood before. They were last seen eight hundred feet shy of Everest's summit. A century later, we still don't know whether they achieved their