I'M GOING AWAY AGAIN, the fourth foreign trip in as many months. My passport has another new tattoo, my arm another needle hole, my vaccination record another stamp. I bought a new journal, the empty pages beckoning like a sculptor's block of clay.

I've read handwritten reports and obscure books and corresponded with one of the few people on earth who's been to the region of China's western Sichuan province where I'm going, 71-year-old Japanese explorer Tomatsu Nakamura. I've printed out the Landsat photos and managed to obtain the uncannily accurate Soviet topos that have guided me on so many trips before.

Before he died in 1995, along with his brother and two friends, when a bowhead whale capsized their boat in Baffin Bay on their way home from an expedition to the Barnes Ice Cap, my best friend, redheaded Mike Moe, told me that "half the joy of a journey is planning it; the other half is coming home and bragging about it." I remember so many nights when Mike and I spread maps across his living-room floor and dreamed big about some distant place; three months afterwards we'd be giving a slide show about our adventure in that same living room, roasting each other to the hooting of close friends. Later, when everyone was gone, we'd stretch out on the rug and plan our next trip.

I have been going away and coming back since I was 16. I blew off my last semester of high school so Mike and I could escape to Europe and Africa and Russia. We traveled till our money ran out, then kept going, scrounging meals in university cafeterias from Seville to Stockholm. Eight months later we made it back to Wyoming to start college.

During my junior year, when I met Sue, the woman who would become my wife, the first thing she and I did was take off to the Grand Canyon for ten days. Two months later I left for three months to bicycle across the U.S. When I returned, we moved in together—Sue was the first woman I'd met who was secure enough to accept my wanderlust and not see it as a threat to our relationship. Several months later I left for a month to ski across Yellowstone, and Sue left to bicycle Europe for six weeks.

Here, gone. Back, gone again. I chose this recursive path, and it has been my life and livelihood for more than two decades. I can't get enough of the world: the stench of sweat on a Tanzanian bus, the sword of wind on an Andean pass, a little girl in the Sahel carrying her baby sister on her back and a bucket of brown river water on her stiff-necked head.

My gusto for journeying and writing about it has remained inextinguishable—and yet something else, something corded to travel like ligament to bone, has changed over the years: my connection to home.

In my twenties I hardly gave a thought to home. I was wild and self-centered and left without a look back. I remember standing around a campfire in the Tetons, snowflakes hooking together in midair and parachuting to the ground. One of our clan had just learned that his girlfriend was pregnant.

"I'm not going to let it change me or my life," he declared. "I'm still going climbing and kayaking and skiing!"

"Here, here!" We all toasted his commitment to the heroic, self-absorbed dirtbag life.

In 1991, when Sue was pregnant with our first daughter, Addi, I was kayaking down the Niger River, running a gantlet of hippos and crocs. I'd left in the middle of the second trimester. When I'd expressed my misgivings, Sue had dismissed the issue. "Pregnancy isn't an injury, Mark," she said. "I'll be just fine."

And she was. She was focused on her passions—teaching Spanish at the university, volunteering in the community, working on our old house. I was back for the birth, but a part of me still wanted to believe that home was wherever I happened to lay my head.

I was forever stripped of the sophistry of this notion when Addi was 20 months old. I was leaving for Tibet with three friends to attempt an unclimbed 19,296-foot peak called Hkakabo Razi. It was a dangerous undertaking with an uncertain outcome. I didn't have to go—I wanted to.

Innocent of my imminent departure, Addi, a weeble-wobble toddler, helped me pack. She drummed the black camp pot with ice screws, waddled up and down the hall dragging my climbing slings and carabiners, flung her chubby, diapered body into my minus-40-degree down sleeping bag, pealing with delight. For her, it was just another game. But I was scraped raw by my duplicity. I didn't have the heart to tell her what was really happening: I was leaving.

At the airport, watching planes take off, Addi suddenly figured it out. "Daddy . . ." she hesitated, and her lip began to quiver.

The look of shock and hurt and betrayal in her huge brown eyes crushed me more than any avalanche ever could.