Each step was more futile than the last. I was in central Alaska on a sliding slope of loose rock, and the pebbles underneath offered little traction. Out of breath, legs burning with lactic acid, I hung my head in disgust -- and my 40-pound backpack slumped forward over my head.

Brett, my younger brother-in-law, scampered down the slope and offered to carry my pack. He was still wearing his. "Hey, don't sweat it man," he said. "You're tall. You're not built for this kind of stuff."

It's true. I stand 6-foot-4. But I didn't feel tall. I felt weak.

The trip to the backcountry wilderness of Denali National Park -- a 30th birthday present from my wife, Amy -- was supposed to be a celebration of my enduring youth and vigor. Instead, I feared I was sliding into middle-aged foppishness.

The trip started on a considerably higher note. After a two-hour ride on a school bus, my brother-in-law, his buddy Russ and I were dropped off at the Eielson Visitor Center, where we began a three-day hike.

Setting out into the backcountry felt like being set free. Not that I didn't relish every moment of the prior year, when my wife gave birth to our first child. But baby care leaves little time for wilderness excursions. I was restless, so Amy sent me to Alaska.

Our plan had been to hike onto a glacier amid a ring of 7,000-foot mountain peaks, thread a mountain pass and return down a different side of the glacier.

It was late in the day when we reached the circle of peaks. The sun had dipped below them, casting a gray pall. I was standing on a glacier -- rock and ice. It looked like we were preparing to encamp on the moon.

By morning, our water bottles were frozen and my thermarest mattress had popped and deflated. My spirits deflated, too, when I got a good look at our mountain pass -- steep and imposing, even if it wasn't snow-covered.

Brett shouldered his pack and strode up the scree slope with confidence and swagger. His buddy Russ -- fresh from several weeks of backpacking on the Colorado Trail -- assembled his trekking poles and perfunctorily picked his way up the hill like a mechanical hiker in a German cuckoo clock. Brett's only a year younger than me; Russ only a few years younger. But they're bachelors, which means they can hit the gym after work and go on monthlong walkabouts. I prefer to spend my free time with my wife and kid.

I was about halfway up the slope when the scree slid out from under me. Then Brett took my pack (and some of my pride with it) and shimmied up to a boulder.

I swallowed hard and crawled toward the same spot. That's when I noticed rocks were falling from above, shaken loose by soundwaves from our climb. As I hustled toward Brett, a baseball-sized rock hit my ankle. Then, a volleyball-sized rock tumbled by and exploded below.

This is nuts, I thought. I grew up fatherless because my dad was an alcoholic. I'm risking the same fate for my son, Anders, because I'm too stupid to know my own limits.

"Brett, I shouldn't be doing this," I admitted. "Amy and Anders need me more than I need to get over this mountain."

Brett looked at me, looked up at the mountain pass, then looked at me again. He's my son's godfather.

"Damn!" he said. "All right. Hey, Russ, let's go back down."

Bears for breakfast

By self-imposed penance, I got up early the next morning to cook breakfast -- pancakes laden with tundra blueberries. As I mixed the batter and made coffee, I noticed a boulder in the willow bushes a few yards from camp. Then I saw the boulder move. It had a head.