IF WE HAD ONE PERSON TO THANK FOR GETTING US here—and to blame when the weather turned—it was Montana road-bike racer M.C. Jenni, Boojum's office manager. She had fantasized about mountain-biking across a Montana without roads, and encouraged her boss to try out such a trip in Mongolia. No one doubted her abilities. After all, she'd completed the Hewlett-Packard LaserJet Women's Challenge—a 12-day, 750-mile stage race in southern Idaho. But she'd never guided before, so Boojum paired her up with the ever-ready Peter Weinig.

Four years ago, Weinig, a native of Germany, had ventured solo out of Ulan Bator on a horse loaned to him by the Mongolian Boy Scouts; except for winter getaways, he hasn't shaken Mongolia yet. He's been leading Boojum's equestrian trips in Mongolia for three years, but bike saddles suit him just as well. "I've got a bike in Delhi, a bike in Berlin, one in Singapore, and one here in Mongolia," he boasted as we unloaded our gear from the plane in Mörön. But, he added, "This is the place with the real choice riding."

Rounding out the expedition were six American clients and six Mongolians, the latter of whom we addressed by their first names. (Mongolian surnames tend to be too difficult to pronounce.) Among them were Bold, a young translator who'd learned English from a drifting Oregonian Rasta; Maagi, the patient and quiet cook; and Mishig, Boojum's Mongolian business partner. Mishig holds a 20 percent stake in the Boojum-owned Khovsgal Lodge Company; he also serves as in-country ambassador and auto mechanic. On this trip, he drove an army surplus Russian GAZ 31 truck, a four-wheel-drive support vehicle. When Mishig wasn't driving, he fished from the riverbanks without a rod, spinning the line overhead like a lasso before sending the glittering lure out across the current.

We strung out in Technicolor shapes on the gray and brown hills and spent the first four days in sunny, clear weather. Then, on the afternoon of our fifth day, we left the rolling grasslands and felt the chill of the Saridag Mountains ahead. Melted snow and frost turned our ascent into a slushy mess, and snowflakes soon blanketed our helmets. Passing one of our riders toppled in a puddle, Jenni shouted, "Spring skiing!"

And yet our arrival at Lake Khovsgal that evening was so dramatic it overshadowed the storm. The 600-foot-deep lake was stunningly clear. Its water is rumored to be so clean that—all my outdoor training notwithstanding—I drank straight from a water bottle filled at its edge.