NONE OF US HAD MUCH TO SAY as we followed the glacier up to the mountain's lower slopes. We thought we knew what risks we were facing. Still, our ignorance was staggering. Our bodies were ravaged, and we had no mountaineering skills whatsoever: Instead of making our way up a gentle saddle to the south, for instance, we set off straight up the mountain's steepest slopes.

The snow was firm, and the cleats of my rugby shoes bit well into the frozen crust. But soon the surface began to weaken and we were forced to wade uphill through heavy drifts. My snowshoes quickly became so soaked that I felt as if I were climbing with manhole covers bolted to my shoes.

By midmorning we had worked our way to a dizzying altitude. But after five or six hours of hard climbing, the summit seemed no closer. My spirits sagged as I gauged the vast distance to the top. But as my body begged for surrender, some deep instinct forced me into a madman's pace. Step-push, step-push. Nothing else mattered. I was a locomotive lumbering up the slope. I was lunacy in slow motion. Soon I had pulled far ahead of Roberto and Tintin, who had to shout to make me stop. I waited for them at an outcrop. We ate some meat and melted some snow to drink. We all knew the kind of trouble we were in.

"Do you still think we can make it by nightfall?" Roberto asked. He was looking at the summit.

I shrugged. "We should look for a place to camp. If we don't find shelter, we will freeze before morning."

Roberto rose and lifted his backpack. "What did we do to deserve this?" he muttered. Then we started to climb.

It was late afternoon now, and the temperature began to fall. By twilight I was starting to panic, and I scaled a tall outcrop to get a better view. But as I pulled myself up, a rock the size of a cannonball broke free.

"Watch out! Watch out below!" I shouted. I looked down to see Roberto, eyes widened as he waited for the impact. The rock missed his head by inches. "You son of a bitch! You son of a bitch!" he shouted. "Are you trying to kill me? Watch what the fuck you're doing!" Then he leaned forward, and his shoulders started to heave. Hearing his sobs, I felt a stab of hopelessness, then I was overtaken by a sudden, inarticulate rage.

"Fuck this! Fuck this!" I muttered. "I have had enough! I have had enough!"

Finally I found a shallow depression in the snow beneath a large boulder, and we spread out the fragile sleeping bag, sewn together crudely with copper wire.

"Did you pee?" asked Roberto. "We can't be getting in and out of this bag all night."

It reassured me that Roberto was his grumbling self again.

"I peed," I answered. "Did you pee? I don't want you peeing in this bag."

Roberto huffed. "If anyone pees in the bag it will be you. And be careful with those big feet."

I tried to get comfortable, but I was far too frightened and cold to relax.

"Roberto," I said, "you're the medical student. How does one die of exhaustion? Is it painful? Do you just drift off?"

"What does it matter how you die?" he said. "You'll be dead, and that's all that matters."