OUR BIKING GROUP IS A COLORFUL CREW. Along with Boyer and Clignet, there's Kelly Crowley, 30, a world-champion Paralympian in women's swimming and cycling, with an underdeveloped right arm, who used to be Ritchey's next-door neighbor. There's Ritchey's old friend Kevin Cusack, a 51-year-old Michigan investment manager, and Doug Grant, a happy-go-lucky guy from Orange County who held a Project Rwanda fundraiser ride on his 50th birthday and raised $30,000. There's also a small group from a Christian charity called Kids Across America—all wearing matching white safari shirts—here to launch a U.S.-style sports camp.

Our first ride happened two days into the trip. After a quick group photo taken about an hour outside Kigali, zoom: We were off down a steep, bouncy dirt road. The landscape was astonishing—sumptuous valleys thick with green-tea plantations and dense eucalyptus forests; jagged, cloud-lined cliffs; steep waterfalls that dove into shimmering rivers and lakes. At times it looked like Brazil meets Switzerland meets Maui.

Let me admit right here that I didn't know what I was getting myself into. I've been riding road bikes for a few years now, racing as a thoroughly mediocre amateur for the past two. But I live in New York City, and I've hardly done any mountain biking. Ritchey doesn't exactly subscribe to the everyone-sticks-together theory—consciously or not, he likes to floor it and see who hangs. After a half-hour or so, I was dropped and depressed. Then it dawned on me: Up the road were a five-time Tour de France competitor (Boyer, who's also won the Race Across America twice), a six-time world champion (Clignet), and Tom freakin' Ritchey. It wasn't like I was riding with three chumps in cargo shorts.

And then she appeared, from out of the woods—a barefoot girl around five years old, dressed in a rose-colored smock. She began to run alongside me, smiling.

"Where are you going?" she asked in English.

"Ruhengeri," I said, though I was sure I'd totally mangled the pronunciation.

"Where are you going?"

"Ruhengeri."

"Why?"

"To sleep."

"Why?"

And on we went. I crawled along in a low gear; she hopped along, with no shoes, for at least a mile, into one village, then the next. Later, Boyer would tell me that many of the people we encountered on the mountain roads rarely stray more than 20 miles from their homes, never seeing larger cities like Kigali or Butare. I could not imagine what I must have looked like to the girl. In my white helmet, bug-eyed sunglasses, and black-and-yellow spandex uniform, I was a superfreak, a fact confirmed when I rode into the next village, where a young boy perched on a bluff let out a buoyant scream:

"MUU!"

(Inhale.)

"ZUUUUNNN!"

(Inhale.)

"GOOOOOOOO!"

As in mzungu, Swahili for "white person." This is what I would be called throughout the trip—at least 150 times a day before lunch. Not only is it accurate; it's clearly a very fun word to say, because as soon as the first kid let loose with a "Muuzuungooo!" there was another one saying it, and another, and another, until there was a formation of a dozen kids bouncing alongside my bicycle, giggling at my ridiculous getup and marveling at the fluke of my pigmentation.

I rolled into the village pursued like a tabloid celebrity. Ritchey and the gang were already there; he'd flagged down what appeared to be a wooden bike assembled by Hummer. The thing was at least six feet long. "I've never seen one like this before," he said. "Would you look at those bearings? Those are from, like, a truck."

I'd started to notice something unusual. In this village and all along the day's route, we'd encountered tons of kids—there was a massive baby boom after the genocide, and 42 percent of Rwanda's population is under 14. We saw old folks, too, but what you don't see a lot of are people in their thirties. It's a sad realization: There really is a missing generation here.

When I pedaled wearily into Ruhengeri as darkness was falling, I headed into the red-brick guesthouse where we were staying and peeled off my spandex. And for a moment, I started to tear up. Not because I felt grimy and exhausted (which I did), or couldn't believe we'd have to ride this hard again the next day (which we would), but because I was overwhelmed. Earlier, Ritchey had told me, "You can't leave this place untouched," and I could already see he was right.

So I had a little cry. Then I stepped into the shower, lost my balance, slipped and fell on my ass, feet over head, and slammed my skull hard into the porcelain with a dramatic thwap. And I laughed, loudly, for what felt like an hour.