THAT NIGHT the temperature dropped so low that the bottle we were using to melt snow shattered. In the morning we placed our frozen shoes in the sun until they thawed. Then we began to climb. The sun was bright. It was our second day of perfect weather.

With every hundred yards, the incline tilted closer to vertical. The tug of the void was constant. My life had collapsed to a simple game—climb well and live or falter and die. The calm voice in my head had become my own.

Put the left foot there. Now, reach up for the crack in that boulder. Is it sturdy? Good. Lift yourself. Trust your balance. Watch the ice!

I had never felt so focused, so fiercely alive. In those astonishing moments, my suffering was over,

I would walk through that godforsaken country with love in my heart. I would walk until I had walked all the life out of me, and when I fell, I would die that much closer to home.

my life had become pure flow. How we continued, I cannot say. But all day we struggled toward one false summit after another, only to see the mountain soaring up again toward the clouds. We pitched camp well before sunset, and in the morning decided that Tintin and I would try for the summit while Roberto waited with the packs. After hours, we found ourselves at the base of a cliff towering hundreds of feet. Its face was almost dead vertical, but it was coated with hard-packed snow.

"How can we climb this?" asked Tintin.

I studied the wall. My mind was sluggish, but soon I remembered the metal walking stick strapped to my back.

"We need a stairway," I said. Using the tip of the pole, I began to carve crude steps into the snow. Climbing these like the rungs of a ladder, we continued up. Dig, climb. Dig, climb.

Hours passed. Sometime in late morning I spotted blue sky above a ridgeline. After so many false summits, I kept my hopes in check, but this time the slope fell away and I found myself standing on a gloomy hump of wind-scoured snow.

I don't remember if I felt any joy in that moment. If I did, it vanished as soon as I glanced around. The horizon was crowded in every direction with snow-covered mountains, each as steep and forbidding as the one I'd just climbed. I understood immediately that the Fairchild's copilot had been badly mistaken. We had not passed Curicó. We were nowhere near the western limits of the Andes. Our plane had fallen somewhere in the middle of the range.

In that moment, all my dreams, assumptions, and expectations evaporated into the thin Andean air. I had always thought life was the natural thing, and death was simply the end of living. Now, in this lifeless place, I saw with terrible clarity that death was the constant, and life was only a short, fragile dream. I felt a sharp and sudden longing for my mother and sister, and for my father, whom I was sure I would never see again. But despite the hopelessness of my situation, the memory of him filled me with joy. It staggered me—the mountains could not crush my ability to love. In that moment, I discovered a simple, astounding secret: Death has an opposite, but it is not mere living. It is not courage or faith or will. The opposite of death is love. How had I missed that? How does anyone miss that? My fears lifted, and I knew that I would not let death control me. I would walk through that godforsaken country with love and hope in my heart. I would walk until I'd walked all the life out of me, and when I fell, I would die that much closer to home. Using the lipstick as a crayon, I wrote the words MT. SELER on a plastic bag and stuffed it under a rock. This mountain was my enemy, I thought. And now I give it to my father.

Soon I heard Tintin's voice from below.

"Do you see any green, Nando?"

I called back. "Tell Roberto to come up and see for himself."

It took three hours for Roberto to climb up. He looked around, shaking his head. "Well, we're finished," he said flatly. "Look down," I said. "There is a valley. Do you see it?"

The valley wound through the snowy peaks ahead of us, then split into two forks as it neared a pair of smaller mountains. "That must be 50 miles," Roberto said. "How can we make such a trek?"

"Chile is there," I said. "It's just farther than we thought."

It looked hopeless, but we formed a plan. Tintin would go back to the crash site, leaving us his meat, while Roberto and I carried on. That evening, the Andes blazed with the most spectacular sunset I'd ever seen. The sun turned the mountains to gleaming gold, and the sky was lit with swirls of scarlet and lavender.

"Roberto," I said, "can you imagine how beautiful this would be if we were not dead men?" I felt his hand wrap around mine. I knew he was as frightened as I was, but I drew strength from our closeness. We were bonded like brothers. We made each other better men.

In the morning, we stood on the summit. "We may be walking to our deaths," I said, "but I would rather walk to meet my death than wait for it to come to me."

Roberto nodded. "You and I are friends, Nando," he said. "We have been through so much. Now let's go die together."

We eased ourselves over the western lip and began to make our way down.

On December 20, 1972, their ninth day of trekking, Nando Parrado and Roberto Canessa stumbled upon a shepherd's camp in the Chilean region of Los Maitenes. Two days later, Parrado led helicopters to the 14 remaining survivors. Parrado's first account of his story will appear in Miracle in the Andes, from which this article is adapted. The book, co-authored with Pittsburgh-based writer Vince Rause, will be published by Crown on May 9.