We found Boskoff ’s diary, which revealed plans to start at the village of Zhangna on November 10, and then spend two weeks climbing in the Genyen valley. The driver confirmed that he had dropped them off on November 11, but at Lamaya, not Zhangna, with plans for them to call for a pick-up on November 24. According to him, when that call didn’t come, he thought that maybe they had said December 24. (He was likely “confused” over the date because it’s illegal to run an unlicensed guesthouse.) However, as we’d hoped, the promise of $4,000 had broken his reticence.

That afternoon, we made the four-hour drive from Litang to Lamaya, with a team of 12 searchers, mostly Tibetan trekking guides, as well as the driver. Early on Christmas morning, we set off along the path the driver said he’d last seen the climbers take. As one of the two main trails to the Lenggu monastery, the route was well-used and deeply rutted. We passed three pilgrims heading to Genyen; they’d take a step, drop, fully prostrate themselves, stand up, and then repeat the process. Stopping at every village and nomad encampment to glean info, we spent a day and a half trekking into the monastery, about 900 meters higher and 10 miles from Lamaya. Finally, close to the monastery, we met a herder who recalled a foreign man and woman walking up the Genyen valley about a month previously. He tentatively ID’ed Fowler and Boskoff in a photo.

At Lenggu, we set to work, interviewing the two monks who claimed to have met Fowler and Boskoff on November 13. They showed us where the pair had camped, a short walk above the monastery, and described the pair’s equipment in accurate detail.

Having seen the conditions — the cold, the snow, the avalanche chutes in the valley — we braced for the worst. The monks told us that it had been snowing when Boskoff and Fowler arrived and had continued to snow for three days thereafter, with about six inches total accumulation. This, they mentioned, was enough to set off frequent avalanches on Genyen, the pair’s most likely destination.

Genyen, a glacier-clad giant among a sea of proud rock spires, is the most accessible and striking objective in the valley. Although Genyen had been climbed previously — first by a Japanese team in 1988, and most recently in the spring of 2006 by an Italian team — it had only been done via fairly easy routes, with immense scope for interesting, more direct, 900-meter mixed routes on the steep east face.

Lenggu monastery sits at 4,200 meters, directly below this face, with Genyen’s long summit ridge running parallel along a south-north axis to the main summit, 2,000 meters higher. A flat bench crosses the east face at around 5,200 meters, above which the technical difficulties begin. This bench would have made a great basecamp, but also acts as a catchment for the entire wall, which is crowned by cornices and overhanging seracs.