Fifty years ago this week, Sir Edmund Hillary went to Nepal on a mission to what was left of the unexplored world. Last Friday he returned. Flown to Katmandu for the anniversary festivities after spending a week with the family of Tenzing Norgay, his partner in conquest, an exhausted Hillary was wrapped in a blanket and spirited away from the 200-some Sherpas, admirers and reporters awaiting him at the airport. His 83-year-old body was too worn out for travel by plane, much less by foot. But his quest went on, in the form of four Sherpas and a one-armed climber named Gary Guller, who had reached Everest's summit an hour earlier. Thirty-five others had gotten there the day before, and by June, when the mountain closes for business, an estimated 400 people will have ascended to its peak--this year alone. Hillary will not be among them but his spirit undoubtedly will.