At the 11th hour, the day before departure, my partner bailed. Something hadn't been right from the beginning—the tone of his voice on the phone, the odd nonchalance toward planning our gear and food. I felt it in my gut, but my head ignored the signals. We almost always know what's really going on; we just don't want to admit it.

I hardly remember the excuse now. A job interview. Or was it his girlfriend, his mother, money? It doesn't matter. An excuse is just that. At the last minute, he wasn't going to Bolivia. The question was, was I?

My plane ticket was in my pocket, pack packed, time carved off the calendar. I could have canceled, but I was itching for another expedition. Besides, I'd told my friends I was off to Bolivia to climb. I boarded the plane early the next morning and ordered two $3 beers to toast my resolve.

In the prideful world of international climbing, South America isn't cool. The Himalayas are cool. They've got cachet. They're celebrity mountains, shiny and famous as Brad Pitt. Say you're off to Nepal or Tibet and you are immediately conferred a certain exaltedness. But you wanna know a secret? In many ways, South America's better. No permits, no peak fees, no porters. No feckless bureaucrats, no avaricious liaison officers, and best of all, no endless weeks of headachy acclimatization just to slog another mile higher in the sky. South America is five times cheaper and five times more accessible; in general, your chances of summiting are higher. You just have to decide whether you're climbing for the sake of climbing or to impress your friends.

I, of course, was climbing for the sake of climbing.

Bolivia is a hard brown landscape beneath a harsh blue sky; La Paz, its capital, a wild city beneath wild peaks. I felt right at home. Every morning I'd do my daily pull-ups on a pipe in the bathroom of my high-ceilinged pension, and then lace on my boots and run from the mercado, at 12,000 feet, up to the 14,000-foot rim of the Altiplano. Past the European buildings with their tiny balconies and tall shutters, up past the whitewashed homes of the middle class and into the shantytown of tin, plywood, and plastic. Atop the Altiplano I'd stop to stare eastward at the Cordillera Real, a white spine of 6,000-meter Andean peaks, and then descend back into the haze of the city, moving fast, working the thighs. Just like running stadium stairs at home. Back at the market I'd put away a half-dozen Quechuan tacos, three bottles of Fanta, and a banana.

In the afternoons I'd traipse from one pension to another looking for a new climbing partner. I was certain I'd find one. Expeditions are always falling apart; illness, injury, or attitude will knock out two or three people and pretty soon the whole trip is in shambles. I figured I'd have my pick of alpinists. But it wasn't so. The few Americans I found were either aimless, dreadlocked pilgrims or eager but inexperienced clients of guided climbs. And all the European teams seemed to have their shit together. A four-man Austrian expedition was heading for 20,873-foot Illampu, their packs so small it looked as if they were on a day hike. Two experienced Spaniards, inseparable partners, were bound for Ancohuma. A Swiss-French team shut the door when I peeked into their room. There was a huge Japanese expedition that filled up two floors of a pension—one floor for all the climbers, the other for their gear. They wanted me to join their team. I declined. Ditto an offer from a three-man Korean team that had spanking-new gear but didn't know how to start its MSR stove. Both teams struck me as overly zealous, so focused on the summit that they might be tempted to take unjustifiable risks.

Down a cobblestone alley in a shabby old hotel I finally found a three-woman, two-man Slovenian team going to 18,531-foot Condoriri to attempt a new route. They were confident and relaxed. They pulled me into their cramped room to drink wine with them while they loaded piles of Russian ice screws into their well-worn packs. Their leader was a tall, svelte, stunning woman named Ada. She wore a tank top and purple tights, and you could see the muscles in her thighs as she moved around. She had flaming auburn hair, prominent cheekbones, and eyes so dark and beautiful that I was too self-conscious to look straight at her.

“So, where is partner?” Ada asked me.

“I came to Bolivia alone.”

“Ahhh, I see.” She pushed her hair back and lowered her Cleopatra eyes on me. “You come to solo. Very good. Very, very good.”

The other four members of her team nodded at me in respect and admiration. One climber, a towering guy who had stringy hair and a nose that had obviously been broken several times, gave me the thumbs up with hands as hard and large as a gorilla's.

“Stefan also solos,” said Ada, smirking at her teammate.

I'd never intended to solo anything on this trip. I intended to find a partner, preferably one stronger and more experienced than myself. Although I had soloed mountains in the past, soloing was something that took a stronger head than I had. Soloing required gravitas. No backup, no net, no nada; one mistake and you die. I didn't have the screwed-up childhood or soul-wrenching angst or any other useful twisted motivation for soloing. I also didn't have the cojones. But of course, now that I had this instant reputation, I wasn't about to give it up.

“And what are you going to climb?” Ada continued.

My erstwhile partner and I had talked about a dozen different mountains but hadn't settled on anything. On my morning runs I'd studied the two peaks just outside La Paz, 21,201-foot Illimani and 20,340-foot Huaina Potosí. The trade routes on both were known to be interesting and not too technical.

“Huaina Potosí,” I declared.

Ada arched her razor eyebrows, glanced at me and then at her friends. A faint shadow of disappointment crossed their faces.

“The east face direct,” I added, and they all broke into toothy grins and shook their heads in approval, and my tin cup was refilled with red wine.

“To your climb,” said Ada, winking and batting her long dark eyelashes.

I sometimes think back and wonder if she actually knew, somehow, that I'd made it all up on the spot. Nah, of course not. She was just winking at me because she knew she was beautiful and because beautiful women always like bold mountaineers, particularly beautiful women who are bold mountaineers.

That night I went to a good restaurant, La Carreta, ordered myself a big Argentinean steak, and drank one cold beer after another until I was thoroughly convinced that climbing the east face direct of Huaina Potosí was exactly what I'd come to do. Having no guidebook, no map, and only random comments gleaned from drunk climbers, I had no idea if such a route even existed.

I slipped out of my pension before dawn, my pack banging the French doors on the way out, my intentions murky. I walked Avenida Ismael Montes right out of La Paz. From the Altiplano, most of Huaina Potosí was buried in clouds, but the summit was still visible. I decided to hitchhike my way toward it, and so in the first light I hopped into the bed of a dusty truck along with a group of Quechua farmers clad in pointed woolen caps and bright woolen sarapes.

By noon we had rumbled into the clouds. Big wet flakes swirled like miniature paratroopers into the bed of the truck. The driver stopped in a muddy mining town. He wanted more money. Being the obvious rich guy, I gave it to him. The road ended only a few miles farther on, at a stone dam holding back a small reservoir of black water. The farmers slung their baskets onto their backs and set off. I couldn't believe there was farming anywhere. All I could see through the falling snow were walls of wet rock. I tiptoed along the half-moon rim of the dam, followed an aqueduct for some distance, and then a snowy trail up to an icy tarn.

There were two tents in the talus. I got my tent up and had just crawled inside when there came a tap at my nylon door. I unzipped the flap and a large, sunburned hand holding a steaming mug of coffee came through the opening.

“Welcome, American,” said a Slavic-accented voice.

I stuck my head out. It was almost dark. All I could make out was the figure of a broad-shouldered man. I took a drink of the coffee. It was heavily spiked—half coffee, half vodka.

“Russian?” I asked.

“Ach, you offend me.”

“Sorry.” I knew better than to make a wild guess.

“Czech.”

His name was Petar, and within five minutes I was jammed into his tent along with three of his companions. Two climbers in their team had not yet arrived. In the past few days they had reconned the entire lower portion of the east face. I listened intently, taking mental notes on their descriptions of the seracs, the crevasses, the hanging glaciers.

“But now with this storm,” said Petar, shrugging, “the crevasses will be hidden.”

It snowed lightly again the next day. We hung out in our tents, swapping tall tales of previous climbs. That night the weather cleared. On the third day we all stayed in camp, giving the snow a chance to settle. I was just getting ready to ask if I could join their gallant team, when the two remaining climbers showed up. Hugs all around and mugfuls of killer coffee. I was introduced.

“Americaner! Slovenes told us. You come to solo east face.”

I hadn't said a word to my new Czech friends about this ill-begotten rumor. I'd assumed it had disappeared when I did.

Petar slapped me on the back, grinning. “So, Mark, you have been holding your program from us!” he cried.

“No, no…” I laughed. I faltered.

All I had to do was tell the truth. I might lose face, but at least this house of cards built by my pride would be toppled. I took a big slug of coffee. I was about to explain when Petar made an impromptu toast.

“To your climb!”

“To Mark's climb!” they all shouted.

That night the stars were hard and bright as chips of silver. I lay in my tent, peering up through the open flap. It was going to be a perfect morning. I was acclimatized. I was as strong as I'd ever been in my life. In a few hours I would either have to confess or climb.

I pinched my watch and the alarm stopped. I dressed by headlamp. I had been dreaming about the climb: Two men were ascending the side of a mountain in a swirling snowstorm, shouting at each other. They were identical twins, but one was young, the other much older.

“If it gets too bad, you can just turn around!” the young man yelled with anger in his voice.

The old man, his face darkly sunburned, stopped, shaking his head. “No, you can't always just turn around,” he said.

“But you gotta at least try!” the young climber replied.

“You don't know the route,” the old man cautioned.

“So what?” the young man said dismissively. “You never know the route until you do it.”

I replayed the debate as I sat packing my small rucksack by rote. Down coat, spare mittens, water bottle, sardines, cashews, jackknife.

“Ask the Czechs if you can climb with them,” the old man had advised.

“They're already a team,” the youth had objected, kicking in his crampons and stepping up.

I downed a liter of water and a bar of chocolate, and their argument began to fade. It was all academic. I was almost packed. My actions were speaking louder than their words. The decision had already been made. Beware anyone beautiful who winks at you after you've told a self-serving lie—you'll feel obliged to live up to your big mouth.

I had to decide about gear. Rope or no rope. Pro or no pro. Rope and protection go together; it's either all or nothing. I made a pile—harness, 'biners, screws, slings, nuts, cams, rope. Way too heavy. Forget it.

I crawled out of the tent, fastened two ice tools and my crampons to the pack, and started up the talus in the moonlight. I'd gone a hundred yards when I stopped, turned around, and walked back to camp. Second thoughts.

It's never all or nothing. I cut the pile in half. A handful of slings, three ice screws, three nuts, and a 200-foot length of five-millimeter Kevlar rope.

Even with the new snow, I could see a faint trail zigzagging up the ridge. I moved fast, feeling strong, bounding from one boulder to the next. There were glaciers on either side of the ridge, twisted and sharp, like rivers of broken glass. I stayed on the arête, reaching its top by daybreak. The mountain was before me, bathed in pink. It made the walls of snow and ice appear inviting, benign. I popped on my crampons and set off up the glacier.

The sheer angle of the sun was perfect. I could detect the slightest dip in the snow. To the right and left were open crevasses. I traced each avulsion until it squeezed shut, then followed the faint trough to where it intersected my line of ascent. Climbing with one tool in each hand, I made tigerlike leaps every time I thought I was at the edge of a trap. The snow was so stiff and clean my crampons barely left tracks. Everything seemed to be going smoothly. Whenever I looked up I could see my route: across the glacier, S-curves around two icefalls, straight up the headwall, onto the unseen summit.

I was moving around the second icefall when I had the eerie feeling that I was being watched, instinctively looked over my shoulder, and gasped. Clouds. Not just clouds, but a dense cloudbank. The front must have crept up from the Amazon, stealthy and quiet as an assassin. I had been so focused on getting to the summit that I hadn't even noticed.

I quickened my pace, jumping crevasses almost recklessly. The cloudbank unnerved me. In 20 minutes its ominous shadow began to obscure the light I needed to detect the hidden crevasses. The atmosphere of the climb had changed. Roped to a partner it would have been no big deal. Solo, I started to get scared. But I was less than 2,000 feet from the summit—maybe two hours away.

When I got to the headwall there was a gaping bergshrund. This was the place to turn around. I could be back in camp for breakfast with the Czechs. Two big cups of coffee sans the coffee and tell the whole bloody truth at lunch. But I was on autopilot. My ego had taken over the controls.

I walked along the jaw of ice to where it attached to the wall, chose my spot, and leapt, slamming picks and front points into the wall. The ice was ideal—soft as wood. I skittered up the face like a frightened spider, calves and forearms aching. When I gained the ridge, the summit was still almost visible. I could even discern the swooping lines of buried crevasses. I was climbing as fast as I could. I thought only about the summit. Twice I stood on the lower lip of an open-mouthed steep-slope crevasse, leaned out, sank both tools in the upper lip, and cranked over the beckoning blue hole.

I am ashamed to report that I successfully summited Huaina Potosí. On top it was snowing so hard I couldn't see 50 feet. And yet I had a perfect view of my own conceit: It was inexcusable to have kept going, and now getting down was going to be mortally dangerous.

Off the summit pyramid I jumped the crevasses with a combination of dread and determination. I used up all the slings setting V-thread rappels to escape down the headwall. I used up all the ice screws and nuts doing desperate self-belays across the minefield of crevasses. Every rappel, every belay, was made off just one anchor. The entire descent, even more than the ascent, was unjustifiably risky.

When I finally stepped off the glacier onto the rock ridge—safe—my legs gave out from under me and I crumpled into the talus.

Surviving by the skin of your teeth is the stuff of legend. These are the war stories we boast of, as if survival were vindication. But it's not. Just because I summited and got down alive doesn't mean I did the right thing. I'd been a fool. I'd made bad decisions since the day I stepped onto the plane. Surviving after a series of stupid moves is nothing more than the Goddess of Good Fortune taking pity on you. (Don't ask her to do it more than once.) It's nothing to be proud of.

When I could walk again I started picking my way down the ridge, stopping a lot, staying on the trail. I was talking out loud to myself. I swore, over and over, I'd never do something like this again. “Are you listening, Mark?” I'd yell, and then I'd clap myself on the side of the head.

I promised myself that when I got back to camp I wouldn't say a word to the Czechs. If they asked I'd say I'd gone out for a hike, a little recon, something like that. I'd tell them I'd changed my mind about a solo climb, that it was too dangerous. I wouldn't turn what I'd done into some kind of guy-alone-on-the-summit-thrusting-arms-in-the-air hero story. I wouldn't.

Petar was standing outside his tent when I trudged into camp.

“Marco! You did it, didn't you!”

I held my tongue but I was already grinning. I wouldn't. I swore I wouldn't.

Confessions of a Solo Climber