Like most climbers, I grew up steeped in the legend of Mallory and Irvine. Indeed, the long, rich narrative of mountaineering contains no more stirring or enigmatic chapter. As a teenager, clumping up a stony ridge toward the wind-lashed apex of some nondescript peak in my native Colorado, I often conjured up that heroic pair, angling into the sky on June 8, 1924, fighting their way higher than human beings had ever climbed, as they closed in on the summit of Mount Everest.

At that moment, ten days shy of his thirty-eighth birthday, George Leigh Mallory was Britain's finest mountaineer. A man blessed with a preternatural gracefulness, with beauty and charm that dazzled his friends and admirers, he had become obsessed with reaching the highest point on earth. His partner, Andrew "Sandy" Irvine, a relative novice at twenty-two, still an undergraduate at Oxford, had nonetheless proven himself the perfect acolyte in this quest for an alpine grail.

What the leader of the 1924 expedition, on which Mallory and Irvine were lost, wrote afterward rings true today -- Mallory was "the greatest antagonist that Everest has had -- or is like to have." And Irvine, though destined ever after to languish in the shade of Mallory's fame, remains, in the vignette of another teammate, the epitome of the "natural adept.... He could follow, if not lead, anywhere."

At 12:50 on the afternoon of June 8, 1924, climbing solo to 26,000 feet in support of the summit duo, Noel Odell saw the clouds part briefly, giving him a fugitive glimpse of a pair of figures far above him, outlined against the sky, "moving expeditiously" over a steep step of rock and ice on the northeast ridge, less than a thousand feet below the top. This has come down to us as perhaps the most haunting sighting in the annals of exploration. Then the clouds closed in, and Mallory and Irvine vanished into history.

With the sole exception of Amelia Earhart, no lost explorer in the twentieth century has provoked a more intense outpouring of romantic speculation than George Mallory. The question of what happened to him and his young companion, of how those two brave men met their fate, is knotty enough. What spurs the imagination to a higher flight is the possibility that they might have reached Everest's summit before they died -- twenty-nine years before Edmund Hillary and Tenzing Norgay made the mountain's official first ascent. If Mallory and Irvine had succeeded, they could have laid fair claim to having pulled off the greatest mountaineering feat ever performed.

Thus the mystery of Mallory and Irvine was handed down to all later generations of climbers. But for me, at age eighteen, the conundrum took on a more personal dimension. As a freshman at Harvard, I drifted into the circle of the university's mountaineering club, which at the time comprised the most accomplished gang of college climbers in the country. Among the six or seven especially talented and flamboyant upperclassmen, who had already notched their belts with such daunting Canadian summits as Logan, Waddington, and Stiletto Needle, one in particular became first my hero, then my mentor, and then my friend and partner.

Scraggly-bearded, soft-spoken, quicksilver smart, slyly iconoclastic, brilliant on vertical rock and ice, absentminded as a dreamy preschooler, Rick Millikan seemed cut from a Viking mold. On an autumn weekend at the Shawangunks, in New York state, Rick dragged me up the hardest and most exhilarating rock pitch I had yet tackled; that January, he broke trail along the frozen crest of New Hampshire's Presidential Range, as I struggled to keep up in a -30° F. gale.

Sometime during that freshman year, I learned that Rick was George Mallory's grandson. Born in 1941, Rick of course had never known his illustrious forebear. His mother, Clare, the eldest of Mallory's three children, had been eight when her father disappeared. She remembered much about him, and she passed down her stories to her three sons.

As Rick and I became good friends, we sometimes talked about Mallory. He believed his grandfather had summitted that June day so long ago; pressed for a rationale, he fell back on intuition. "Those guys were good," he said, if memory serves. "They knew what they were doing up there."

Rick's other grandfather was Robert Millikan, of the famous oil drop experiment, who had won the 1923 Nobel Prize in physics. Clare Mallory had married Robert Millikan's son, Glenn, only to watch, one day in 1947, as her husband was killed as he stood beside her, in a climbing accident in the Great Smoky Mountains of Tennessee. I knew little more about this catastrophe than the bare facts: Rick's father had been hit on the head by a falling stone, in a fluky concatenation of minor miscalculations on a small cliff in the middle of nowhere. He had died instantly. At twenty, I was too shy and awkward to probe further, or to ask Rick to recount the mishap that had cost him his father at an even younger age than Clare had lost hers.

What seemed remarkable, though, was that despite the twin tragedies of her life, Clare had not only tolerated her sons' embrace of this most dangerous sport -- she had taught them to climb and heartily encouraged their alpine play. On visits to Berkeley, where Rick had grown up, I got to know Clare, who seemed a classic Edwardian eccentric -- a Quaker fiercely devoted to the cause of world peace, a blunt-speaking liberal with no patience for humbug, a true bohemian even in the bohemia of late-1960s Berkeley.

On my first Alaskan expedition, to the Wickersham Wall on Mount McKinley in 1963, Rick and I, with five teammates, were reported missing and feared dead (our bush pilot, poking through storm clouds, had seen our tracks disappear into a chaos of avalanche debris). During the four days we were unaccounted for (we were safely camped far above the avalanche zone), the newspapers interviewed our parents, who gave voice to heartsick fears and hopes against hope. Only Clare was resolutely skeptical, telling the media, in effect, "Nonsense. Those boys know what they're doing."

Three years later, one September afternoon in the Kichatna Spires, southwest of McKinley, as Rick and I got within forty feet of the summit of an unclimbed, unnamed peak, a big wind slab broke beneath our feet. Helpless to slow our fall, we slid and cartwheeled with the avalanche toward a fatal cliff that loomed below. We had time to anticipate the plunge that lurks, like some dark atavistic memory, in the vulnerable core of the blithest mountaineer's unconscious, before the slide, having carried us 350 feet, miraculously churned to a halt a short distance above the precipice.

I am not sure whether, or how, Rick told his mother about our close call, but the very next summer, he was back with me in Alaska, probing an unexplored range we named the Revelation Mountains. This time Rick's older brother, George, whom I had not climbed with before, came along. (George was even more absentminded than Rick, once in grad school inadvertently locking his professor inside a walk-in bird cage.)

For fifty-two days, we endured the worst weather the Alaska Range could fling at us. Only in recent months have I learned that that summer, for the first time, Clare gave in to the fears that every parent knows. She lost sleep counting the days until we emerged at the end of August, and she extracted a promise from George and Rick that in the Revelations they would never rope up together (better, if it came to that, to lose one son than two).

Of course the brothers Millikan, once on the glacier and out of reach of Mom, promptly disobeyed her. One day George and Rick stormed toward the summit of a beautiful peak we called the Angel, climbing fast along an arâte strung with rock towers and ice cliffs. They settled in for the night in a tiny bivouac tent pitched on an airy ledge some 1,000 feet below the top, only to have rain turn to sleet turn to snow whipped by a ferocious wind. Sleepless and hypothermic, they staggered off the mountain the next day, required, in the atrocious conditions -- rime ice over slick granite -- to rappel almost horizontal pitches. The same storm, 150 miles to the northeast, was in the process of snuffing out the lives of seven trapped climbers among the Wilcox party high on McKinley.

Last May, as the electrifying news that Mallory's body had been discovered on Everest circled the globe, I got in touch with Rick and George and Clare, after a lapse of some years. More than ever, as the details emerged, Rick clung to the belief that before his fatal fall, Mallory had reached the highest point on earth. Clare, now eighty-three, had another sort of interest. "I didn't feel anything much at first," she told me. "I felt that my father's body was far away from his spirit. But I've thought about it more and more in the weeks since. I was anxious to know how he had died. Was it peacefully, as he meditated, or contorted, in pain? I found myself wishing I could be there and comfort him in his pain.

"But all in all, I wish they hadn't found him. I wish they'd left him in peace."

After all these decades, I had felt that in a certain sense I "knew" Mallory myself. But as I researched an article for National Geographic Adventure about the discovery, I became acquainted with a man and an explorer even more charismatic, elusive, and remarkable than the mythic figure that had lodged in my head. And as I met and talked to the members of the expedition that had deliberately set out last spring to unravel the mystery of Mallory and Irvine -- before the trip, I would have given them about one chance in 10,000 of finding anything from the 1924 expedition, let alone Mallory's body -- I found a crew of strong, competent, mutually loyal climbers, the kind who do our perilous pastime proud.

Among that crew, however, Conrad Anker stood out. One of the best mountaineers in the world, with an astonishingly varied record of first ascents, Conrad has somehow escaped the megalomania endemic in the world of climbing superstars. He seems instead, at thirty-six, a man firmly grounded in a personal humility; he listens to the cares and needs of others as keenly as to the siren songs of his own ambition; and the Buddhist outlook that draws him toward his Himalayan wanderings has seeped into his spirit, giving him an inner calm. That bedrock stability, that sense of who he is, emerges in the sotto voce notes Conrad occasionally publishes in the American Alpine Journal, his only record of some of the boldest climbs ever ventured. His prose in these well-crafted but understated chronicles is like that of a scholar writing judiciously for an audience of his peers.

In the course of our collaboration on this book, I began to realize that, in a certain sense, Conrad Anker was cut from the same cloth as George Mallory. And it became clear that Conrad had an utterly enthralling tale to tell of Everest '99, his own story of Mallory and the mountain.

In this book, then, Conrad and I hope to give voice to the quest of a mountaineer, using all the skills and instincts that half a lifetime of cutting-edge ascents has ingrained in his very fingertips, who last May almost singlehandedly brought back from Everest more insight into the puzzle of Mallory and Irvine than the efforts of seventy-five years of searchers and theorists put together. As we narrate that quest, we also seek, so far as retrospect and judgment allow, to rediscover Mallory himself, the visionary lost explorer whose body Conrad Anker found, and whose fate we may at last begin to divine.