On May 2, the electrifying news went out to the world that a team of climbers had found the body of legendary Everest climber George Mallory at 27,000 feet, 75 years after he and his climbing partner Sandy Irvine had disappeared 900 feet below the summit. In one widely quoted dispatch about the discovery, climber David Hahn, who was leading the team of five, talked about the danger of trying to find anything at 27,000 feet, with little more than some loose rocks to keep you from tumbling a straight 8,000 feet down the North Face. "Take one step away," he wrote, "and you're not thinking of George Mallory's life, you're worried about your own life."

Later, David, who is my brother, wrote a more detailed dispatch commenting on how Mallory must have spent his final moments after apparently breaking his leg and falling: "crossing his injured leg over the other to give himself some relief" and "composing himself to die." He described finding a letter from Mallory's wife "on his chest, close to his heart." Reading this at home on the Internet, I almost burst into tears.

Like many readers around the world, I have spent the ensuing weeks compulsively logging on and waiting to see what would happen next. One day, it was the discovery of Mallory. A few days later it was David remembering what it was like to descend the terrifying Second Step alone, in the dark, without oxygen (he'd run out) on his 1994 descent from the summit. A few days later, when I thought he was supposed to be resting, I logged on to see that he was off rescuing frostbitten Ukrainians at 3 a.m. As I write this, he's poised for a summit bid, his fourth, on a mountain where one climber dies for every five who make it.

"One of the best pieces of reportage of our time, " the Manchester Guardian has called his dispatches, and many would agree -- but they don't have to log on to a Web site to see if their brother is living or dead. Every new dispatch confirms that he's still alive -- but if six hours go by without a new post, I'm not thinking about George Mallory's life, I'm thinking about David Hahn's.

For most of our adult lives my brother and I have been about as far apart as it's geographically possible to get. I've seen him so infrequently -- the last time was for a couple of hours in 1993, when he came east for the funeral of a friend who had died on Mount McKinley -- that I don't always recognize him in Internet photos and start laughing when I realize it's him. It's one of the ironies of coming from a mountaineering family that my life in New York is seen as slightly incomprehensible, freakishly suspect, even, while his yearly schedule, which has included spending the past three winters guiding on Mount Vinson in Antarctica, is seen as quite normal. The reality is that, aside from a few phone calls and some e-mail, my connection to my brother's life comes entirely from what I can pick up on the Web.

We grew up in California, hiking each weekend: the Pinnacles, Yosemite, Big Sur. Summer vacations were spent in the high Sierra Nevada mountains, backpacking, sometimes with burros or mules to carry the packs. Even after we moved east, at the end of the '60s, we returned to Yosemite, where the dust of the foothills gave way as we climbed to the huge, empty, glacier-carved valleys, cold but dotted with meadows and bright alpine flowers. I can still remember the crowds disappearing as we climbed from Tuolumne Meadows into the Gorge, the lunches of hardtack, sardines and chocolate, with icy glacier water scooped up in cups as dragonflies hovered and we rested on the hot, glacier-polished boulders.

Family tradition was that the burros and mules always escaped at some point, and my father would trek back to get them, while whoever was left stayed put. One year, "whoever was left" was David and me, alone in a high glacial valley for two days. I had always been close to my little brother, who even then was bright and funny and always daydreaming of heroes and Revolutionary War sea battles, always lost in another book about the Bonhomme Richard and her captain, John Paul Jones ("I have not yet begun to fight!"). There was something surreal about being alone with him in this pure, empty place, with little more than lupines and stars for company, but in the pristine quiet there was no loneliness.

We hiked in the East, too, and as I, the eldest, left for college, I began to hear about winter climbing in the Adirondaks, which sounded vaguely uncomfortable, although the ice-climbing pictures my father and brothers brought back were extraordinary: molten sun shining through blue pillars of ice, each glittering shard illuminated as if on frozen fire.

After college, David and I went our separate ways, connected by long talks on the phone or his infrequent visits to New York, where he'd gamely roll out a sleeping bag in whatever empty but atmospheric loft I lived in at the time, counting the minutes till he could get back out West. I had a sense of losing him, in ways I couldn't quite define, and his life seemed to be further and further away, doing things that seemed increasingly dangerous, at least to me.

"David gone," I'd write on my calendar when he went to Mount McKinley, or later, the Himalayas. "David back," I'd write on the expected return date, my stomach tightening as I tried not to think about him at all in the meantime. Why did it take two or three months to climb a mountain? Why did they always seem to be going up to this or that high camp and then coming back down, before going up again? Why was he always gone?

"I made it to the top," he said, after his 1994 trip to Everest. "Doesn't everyone these days?" I asked, genuinely amazed to hear they didn't. He must have thought I was an idiot, but tactful as always, he managed not to convey it.

He led a climb up Everest's North Face in 1998, which was the year he first hooked up with MountainZone to write dispatches about the trip, and for about the first month, even then, I didn't really pay attention. "David gone," "David back," I'd written again on the calendar.

"Is Carolyn following my dispatches?" David asked our father in e-mail. Um, not yet, I thought. Tell me when you're really going for the top and I'll look.

My modem was slow and I hated reading things on the Internet. But I finally dug out the URL, and, to my surprise, found myself alternately laughing and entranced at David's vivid descriptions. Logging on every few days, I rode in my mind's eye what David called "The Valium Hi-Way" to the base camp at the Rongbuk Glacier, transported in an overladen truck "of uncertain origin and maintenance," whose driver "calmly smiles in some direction other than the one you'd like him to be focusing on" as the truck careens on three wheels over roads known to "drop a mile or two to warmer climes."

In his dispatches, I came to smell the burning yak dung the yak herders used as fuel, to hear the tinkling bells the animals wore, to feel the thin air and the cramped tents. I could see the "100-foot-high daggers of white and blue ice" of the North Fork glacial surface that looked, he said, like "sails, or frozen waves" as he and his fellow climbers picked their way past, scrambling on the loose rocks. Shark's teeth, he thought they looked like, with Everest as the shark.

"Look over at Pumori," he wrote about a 23,000-foot mountain nearby, "steep and toothlike, the way kids draw mountains." As the team established high camps, settled base camp squabbles and waited out storms, I found myself marveling at his skill as a storyteller, another thing I hadn't known about him. Where had it come from?

His team prepared for its final summit attempt, announcing there would be no more dispatches till it was over. I knew enough, finally, to know how dangerous the next few days would be, and I knew this might be the last time we would ever hear from him. In that last dispatch I found what I knew he wanted us to see:

"The house I grew up in had a set of stairs. I was a little guy, three or four feet tall, dragging myself up those steps day after day looking to their finish where my Dad had hung a large print of Barry Bishop's classic photo. Taken from Everest's West Shoulder in 1963, it shows two impossibly small humans at the base of an impossibly large and steep chunk of planet, Everest's West Ridge. I got up those stairs thousands of times while my brain was still young and impressionable. I wonder if my Dad ever meant for me to take so literally the implied suggestion that the top of the stairs was only a beginning?"

There was something in there I recognized, just as I recognized a certain glint in his eyes or a tilt of his chin in unfamiliar photos. Our mother had that self-deprecating humor, and that quiet ability to make you feel like you were the most important person on the face of the earth. David knew who would be reading that dispatch, and he was reaching out with the same generosity, something I had thought was lost forever when our mother died on a cold January day in 1972.

If we had gotten together every weekend, it might never have happened, but something about being on Everest had released my brother, washed away some of the sadness, and brought something whole, and he was giving it back to us. In that dispatch, I discovered something about how my brother could climb so high. To truly be ready to make it to the top, he, like Mallory, had to compose himself to die. All was forgiven, all was at peace, and all that was left was the intense concentration for the task at hand: in Mallory's case, death alone in the cold dark night; in my brother's -- well, he made it to 28,000 feet before the weather changed and they turned around.

And now he's there again, and I am logging onto MountainZone each day to see if there's any news. Will they find Irvine and the camera that might show that they reached the top 29 years before Sir Edmund Hillary? Will Conrad Anker climb the Second Step without the Chinese ladder, the way Mallory and Irvine would have had to? Will everyone make it back safely?

It's gripping, exhilarating, frequently funny and sometimes terrifying, like David's account of the day 15 years ago when he met his boss, Eric Simonson. Eric was swept into a crevasse and David was almost ripped off the mountain. Ho-hum, all in a day's work.

But that was before the finding of Mallory. The "adventure level" has ratcheted up a notch since, and with it, my anxiety. One Ukrainian was rescued, horribly frozen ("his eyes rolled back in his head at the pain of his thawing hands and feet," David wrote) but one was lost and is presumed dead. The letter my brother first thought was from Mallory's wife was actually from his sister and brother.

"Dearest George," the letters he kept "close to his heart" read -- a detail so poignant and heartbreakingly personal I can't completely take it in. To spend the last two weeks logging on in mingled fascination and fear is to find a new brother: a surprisingly powerful writer and a quietly heroic climber who knows what really counts, and the underlying message is undiminished by the fact that it's on a little blue screen and not on air-mail stationary with "love, David" at the bottom.

"Sometimes," he wrote about the day he and his boss met, the day they both nearly died, "you can have a big day in the mountains without getting to the top of anything." This, I've learned, is true about a lot of things.