Francys Arsentiev (January 18, 1958 – May 24, 1998) became the first woman from the United States to reach the summit of Mount Everest without the aid of bottled oxygen, on May 22, 1998.
Due to the absence of oxygen supplementation at such high altitude, the two moved slowly and summitted dangerously late in the day.
Details of what happened next are uncertain, but the most plausible accounts suggest that on the morning of May 23, Francys Arsentiev was encountered by an Uzbek team that was climbing the final few hundred meters to the summit.
[2] On the morning of May 24, Briton Ian Woodall, South African Cathy O'Dowd, and several more Uzbeks encountered Francys Arsentiev while on their way to the summit.
Both Woodall and O'Dowd called off their own summit attempts and tried to help Francys for more than an hour, but because of her poor condition, the perilous location, and freezing weather, they were forced to abandon her and descend to camp.
[1] The mysterious disappearance of her husband was solved the following year when Jake Norton, a member of the 1999 "Mallory and Irvine" expedition, discovered Sergei's body lower on the mountain face, apparently dead from a fall while attempting to rescue his wife.
[3] Woodall initiated and led an expedition in 2007, "The Tao of Everest", with the purpose of returning to the mountain to bury the bodies of Francys Arsentiev and an unidentified climber ("Green Boots"), both of whom were plainly visible from the nearby climbing route.