I FEEL A TUG on the rope and look up. Mike is far above his last piece of protection, and the crack has vanished. There are no handholds and nothing to stand on. Most climbers would back down.

"Watch me!" Mike yells, and dives for a thin ledge.

A letter arrived for me from Swaziland. It was 1989 and I was in Novosibirsk, crossing Siberia by bicycle. Mike wrote, "Dear Dostoyevsky the Big Legs—expect you have saddle sores the size of rubles and lungs like a hippo but the KGB has no doubt caught you by now so I'll soon be mounting a daring rescue ..." He went on for several paragraphs in his clumsy handwriting and terrible spelling, and between the lines I knew he was worried about me and that he was really saying he would do anything for me, march to the ends of the earth if I needed him. I missed him so much I reread the letter over and over, asking myself why I never told him how much he meant to me, why I never just told him I loved him.

Mike barely catches the lip of rock.

He belays me up and I lead the final pitch. We're 800 feet above Lookout Lake, but the climbing is relaxing and fun. Mike got the sketchy pitch, the bastard. I realize now that that's why he didn't argue for the first lead.

I reach the summit, lean against a warm slab of rock, bring Mike up, and we sit there side by side, staring out across Wyoming. "Mike, you remember Lhasa?"

He grins, but I can tell it's really a grimace.

We went to Tibet in 1993 to climb an unknown peak, and after two days in Lhasa Mike got pulmonary edema, just like he did when we were on McKinley, except there was no way to go down and his lungs filled up with fluid, and we went to the hospital, but they could only give him a Chinese army balloon of oxygen that he sucked on while we waited for the plane. His lungs were gurgling so badly he couldn't lie down, so he had to sit up all night, but even then he was still drowning from the inside. His face was bloated and gray, and if the plane didn't come in the morning he would die, but he was the funniest he'd ever been. He kept making me laugh, and I was so scared I was sick to my stomach, and when I heard the sound of the plane I began to weep.

Atop the Diamond, feet dangling in space, we are on the roof of our world. We eat the lunches our wives have packed for us and silently observe the landscape that made us: snow and ice and rock and sky. We sit there together for a long time, feeling as close as we ever have.

After a while we coil the rope and pack up the gear and begin discussing our upcoming expeditions. I'm going to Waddington with my friend John Harlin. It took a lot of persuading. His father died climbing the Eiger, and John has spent much of his adult life struggling with what that means. In his early twenties, John had a partner who died while they were descending from British Columbia's Mount Robson. After that, he promised his wife, Adele, and his mother that he would give up alpinism. Going to Waddington with me means he's breaking his promise.

Mike will attempt to ski and bike across the Barnes Ice Cap on Baffin Island with his brother, Dan, and two other good friends of ours, Brad Humphrey and Sharon Kava. I have tried to convince Sharon not to go—I worry that she doesn't have the experience for an Arctic trip—but Mike's enthusiasm is magnetic. It is something we disagree on. Mike believes that self-confidence and sangfroid—both of which he has an abundance of—are more valuable than technical ability. I don't.

I ask him what he fears most.

"Same as ever, bro."

Years ago, Mike confided that his deepest fear was that something would happen to Dan while they were on a trip together. Dan, quiet and happy, the kid who fainted during sex-ed films in junior high, a man who has never said a bad word about anyone, has always looked up to Mike. Mike is the natural-born leader, Dan the disciple.

"I couldn't bear it," Mike whispers.