But as the sun sank behind the great granite serrations of Muztagh Tower to the west, and shadows raked up the valley's eastern walls, toward the bladed monoliths of Gasherbrum, Mortenson hardly noticed. He was looking inward that afternoon, stunned and absorbed by something unfamiliar in his life to that point—failure.

Reaching into the pocket of his shalwar, he fingered the necklace of amber beads that his little sister Christa had often worn. As a three-year-old in Tanzania, where Mortenson's Minnesota-born parents had been Lutheran missionaries and teachers, Christa had contracted acute meningitis and never fully recovered. Greg, twelve years her senior, had appointed himself her protector. Though Christa struggled to perform simple tasks—putting on her clothes each morning took upward of an hour—and suffered severe epileptic seizures, Greg pressured his mother, Jerene, to allow her some measure of independence. He helped Christa find work at manual labor, taught her the routes of the Twin Cities' public buses, so she could move about freely, and, to their mother's mortification, discussed the particulars of birth control when he learned she was dating.

Each year, whether he was serving as a U.S. Army medic and platoon leader in Germany, working on a nursing degree in South Dakota, studying the neurophysiology of epilepsy at graduate school in Indiana in hopes of discovering a cure for Christa, or living a climbing bum's life out of his car in Berkeley, California, Mortenson insisted that his little sister visit him for a month. Together, they sought out the spectacles that brought Christa so much pleasure. They took in the Indy 500, the Kentucky Derby, road-tripped down to Disneyland, and he guided her through the architecture of his personal cathedral at that time, the storied granite walls of Yosemite.

For her twenty-third birthday, Christa and their mother planned to make a pilgrimage from Minnesota to the cornfield in Deyersville, Iowa, where the movie that Christa was drawn to watch again and again, Field of Dreams, had been filmed. But on her birthday, in the small hours before they were to set out, Christa died of a massive seizure.

After Christa's death, Mortenson retrieved the necklace from among his sister's few things. It still smelled of a campfire they had made during her last visit to stay with him in California. He brought it to Pakistan with him, bound in a Tibetan prayer flag, along with a plan to honor the memory of his little sister. Mortenson was a climber and he had decided on the most meaningful tribute he had within him. He would scale K2, the summit most climbers consider the toughest to reach on Earth, and leave Christa's necklace there at 28,267 feet.

He had been raised in a family that had relished difficult tasks, like building a school and a hospital in Tanzania, on the slopes of Mount Kilimanjaro. But despite the smooth surfaces of his parents' unquestioned faith, Mortenson hadn't yet made up his mind about the nature of divinity. He would leave an offering to whatever deity inhabited the upper atmosphere.

Three months earlier, Mortenson had positively skipped up this glacier in a pair of Teva sandals with no socks, his ninety-pound pack beside the point of the adventure that beckoned him up the Baltoro. He had set off on the seventy-mile trek from Askole with a team of ten English, Irish, French, and American mountaineers, part of a poorly financed but pathologically bold attempt to climb the world's second-highest peak.

Compared to Everest, a thousand miles southeast along the spine of the Himalaya, K2, they all knew, was a killer. To climbers, who call it "The Savage Peak," it remains the ultimate test, a pyramid of razored granite so steep that snow can't cling to its knife-edged ridges. And Mortenson, then a bullishly fit thirty-five-year-old, who had summited Kilimanjaro at age eleven, who'd been schooled on the sheer granite walls of Yosemite, then graduated to half a dozen successful Himalayan ascents, had no doubt when he arrived in May that he would soon stand on what he considered "the biggest and baddest summit on Earth."

From Three Cups of Tea by Greg Mortenson. Copyright Greg Mortenson 2005. All rights reserved. Reproduced by permission of Viking Press.