ON A SATURDAY IN JUNE, Haley drives me out to Leavenworth, Washington, for a weekend of climbing in the Cascades. His gray 1997 Subaru Legacy, which the family bought used, looks to be on its last legs. It hasn't had an oil change in 16 months. We arrive at the trailhead amid the smell of burning oil.

Haley has lined up an ambitious weekend—we'll do two multipitch rock climbs in two days, interspersed with 20 miles of hiking, bookended by long drives. Every item, down to a single Gu packet, has been carefully considered, and only the barest essentials made the bag. The 50-meter, 8.5-millimeter rope that we'll use is thinner than is recommended for rock climbing, since it's more likely to be cut on a sharp edge and snap. But it shaved a few pounds off our backs, which is critical, since Haley hikes faster than some people run.

Haley leads me up Outer Space, a meandering route on a 600-foot shield of granite in the Alpine Lakes Wilderness. Above the first pitch, there's a fourth-class scramble across a terraced shoulder to the next belay. It's not especially dangerous, but it's still quite steep. Haley suggests that we just climb it simultaneously, tied together but without a belay anchor, so we can move faster. The idea makes me a little nervous, and I say so. He considers the terrain and then politely suggests again. "Why don't we do this: Why don't you trust my judgment, and we'll simul-climb a little ways?" he says, smiling. "It'll be fine."

I'm reminded of something Cordes wrote in an e-mail before I went to Seattle: "For sure, there's a bit of a question as to what will happen with Colin." He might keep going at his breakneck pace, he might quit climbing altogether, or he might get killed—as might any climber at the top of the game. "After all," Cordes wrote, "corny as it sounds, that unknown is the very essence of hard alpinism."

It's also why we watch or, in whatever pedestrian way we can, follow. Haley turns and resumes climbing. The thin rope grows taut between us. I dismantle our anchor, take a breath, and follow him onto the ledge.