SARHADD, ROUGHLY HALFWAY up the Wakhan Corridor, is at the end of the road. From here all travel would be by foot or horseback. We had 80 miles in front of us to reach Tajikistan.

On a cold, windy morning, Sarfraz, Doug, Teru, and I left Sarhadd with four packhorses and four Wakhi wranglers. For two days we hiked along the bottoms of immense canyons, in the shadows, jumping boulders, fording side streams, imagining Marco Polo doing the same thing. We climbed two small passes to escape the canyons and reach the upper Wakhan settlement of Langar and Khan Bibi's grim stone hut.

From Langar we walked to Bazai Gonbad, a Kirghiz burial ground consisting of a dozen domed, chalk-white mausoleums. Beyond Bazai Gonbad, the Wakhan widens dramatically. The valley is too high for farming—12,000 feet—hence the eastern Wakhan is inhabited primarily by Kirghiz nomads. In general the Kirghiz are wealthier and healthier than the Wakhi, although ever since the borders were closed in 1949, there has been a symbiotic relationship between the two peoples. The Wakhi need animals and the Kirghiz need grain, so they barter.

The Kirghiz are cowboys, and Sarfraz, a great rider himself, managed to get us saddle horses. Teru, the New Yorker, was the most natural cowboy among the Americans, followed by Doug, who is originally from New Jersey. I grew up in Wyoming working on ranches and can't ride a horse to save my life.

The upper Wakhan is one of the last refuges for at least three endangered species—the snow leopard, the Himalayan wolf, and the Marco Polo sheep. All are still hunted by the Kirghiz. (We saw wolfskin coats for sale on Chicken Street in Kabul and were told the pelts came from northeastern Afghanistan.) In a heavy-snow winter, the Kirghiz hunt snow leopards and wolves that prey on their sheep, and sometimes even on children; they hunt the sheep for food. But change is coming: Biologist George Schaller, vice president of science and exploration at the New York–based Wildlife Conservation Society, has been inventorying Marco Polo sheep in the area since the 1970s—most recently visiting in 2004 and 2005—and he's campaigning to make the entire region a protected international park.

One evening we stopped in a Kirghiz camp called Uchkali, "Place of the Ibex," where there were nine families living in nine yurts and an untold number of goats and sheep and yaks. Kirghiz lives are interwoven with the lives of their animals, and they subsist almost entirely on red meat, milk, and yogurt. Although they speak a Turkic dialect, their ancient ancestors may have been Mongols. After welcoming cups of tea, the old chief, a man named Yeerali, set before us a battered cardboard box. Inside the box was a gas-powered generator.

Yeerali had bought the generator the previous autumn, along with several gallons of gas and a box of electrical supplies, and brought them here by horse in hopes of having lights during the long, snow-buried winter. Of course the generator broke soon afterwards and the camp spent another winter in darkness.

We were Americans, were we not? Visitors from the land of machines. Certainly we would fix the generator.

After having been given so much by the people of the Wakhan, it was our chance to give something back. Besides, we were on the spot. Doug and I took up the challenge.

First we carefully examined the little beast, talking back and forth in a professional tone, making a good show of our diagnosis. Then we got out our multitools and went to town. We fiddled with the gas mixture and the throttle spring and the adjustment screws and the choke lever and the spark-plug gap.

The machine was no more complicated than a lawn mower, but the gaze of the entire camp was on us. After we'd done all we could possibly think of and then some, I yanked on the pull cord.

Nothing. The Kirghiz's disappointment was palpable.

We fiddled some more, I pulled the cord: a cough. Their eyes lit up. More adjustments, I pulled the cord, and the little engine that could roared to life.

Doug and I were instant heroes. Yeerali ordered two men to kill the biggest sheep of the herd, which they did forthwith, cutting its throat and skinning it right there in front of us. While the various parts of the sheep were being cooked, Doug and Sarfraz and I dug into the box of electrical supplies and proceeded to electrify the camp, stringing wire and lights to the nearest yurts as if they were Christmas trees.

When the platter of food arrived, we sat down beneath the abundant light of a single dangling bulb.

Now, there's something special about Wakhan sheep, a Central Asian breed called turki qoey: They have two distinct camel humps of fat on their behinds. Like whale blubber to the Inuit, sheep-ass fat is a delicacy to the Kirghiz.

Two large lumps of steaming ass sat in the middle of the platter, surrounded by the boiled head and testicles.

Doug and I glanced at each other and, without hesitation, sprung open our belay knives, cut off large slices of greasy butt fat, and plopped them into our mouths.

"Not bad," said Doug. Then he cracked open the sheep's head and took a bite of the hot, soft cheek, and I ate one of the big, slippery testicles.