THE VISION
Earlier this year, while thinking about various fun ways to spend the spring climbing season in California, Tommy Caldwell settled on a doozy: First, he and a partner would try the most continuously difficult big-wall free climb they could find, a 28-pitch route up Yosemite's El Capitan, called Magic Mushroom, which looked to rate a 5.14. Then, if all went well, Caldwell would return to lead every rope length himself, during a 24-hour supported speed run.

The origins of the project went back much further than that, though, and it's fitting that Caldwell's grand notion came to him when he was collapsed inside a tent, completely wasted after 24 hours of climbing few others could have even attempted, much less pulled off.

It was October 2005, on a warm, dry day in Yosemite, and Caldwell had just stacked up a pair of 3,000-foot free climbs on El Cap, making all his vertical progress using nothing but the strength of his body and limbs, the gear there only to protect him in case of a fall. His wife, renowned climber Beth Rodden, along with a pack of friends and climbing media, had met Caldwell up top, where his arms were so flushed with blood and lactic acid that they'd gone numb. Three weeks later he developed cluster headaches, and for more than a month his left elbow refused to straighten.

Caldwell had set out at just past 1 A.M. on October 30, starting on the Nose, a 2,900-foot 5.14a and the first line ever climbed on El Cap, back in 1958. (See "Number Crunching," page 108, for a guide to climbing's rating system.) It was originally done by a cantankerous road surveyor named Warren Harding as a direct-aid climb, in which the climber puts weight on his protection hardware as he ascends, standing in stirrups called etriers to place each subsequent piece. Harding and various partners had needed 45 days over two climbing seasons. Caldwell, with belaying assistance from Rodden, did it in 11 hours. While he spidered up the wall, she managed the ropes rapid-fire in his wake, using self-ratcheting ascending devices called jumars as she pulled out the protection he left behind—hand-placed metal widgets called nuts and cams. After jumaring the length of the rope, she'd stop to belay his line at each new anchor as he led off onto the next rope-length pitch.

At 1:36 P.M., Caldwell went back down to El Cap's base and swapped partners, moving on to the 5.12d Freerider with Chris McNamara, a California-based climbing-guidebook publisher. Around 9 P.M., 28 pitches up Freerider, Caldwell came to a final obstacle on a smooth, 5.12 dihedral—a 90-degree, open-book-shaped convergence of two vertical faces. McNamara watched as Caldwell, after two falls, began to "stem" his way up the smoothest part of the dihedral, placing his legs in a splits-style bridge position, crab-walking as he applied force on the opposing walls. He made it through on his third try, going on to summit at 12:26 A.M. on Halloween.

The physical toll of this twofer was clear: Up in the summit tent, Rodden stood watch for two hours, waking Caldwell periodically to make him eat, so he'd have energy for the treacherous scramble and rappel down the East Ledges.

Even in his exhausted daze, Caldwell realized something: He could have pushed harder. Seventy percent of the climbing had been "only" 5.10 or 5.11—no-brainer stuff for an elite climber. What he really craved was an El Cap climb so relentless, pitch by pitch, that to do it in less than 24 hours would demand not only his best physical efforts but also a complicated mental and logistical game.

It would take him another three years to find the right target, and the project he settled on—Magic Mushroom—was a challenge for the ages. I'd heard about Caldwell's ambitions, and I wrote him to propose that he let me watch him plan and train from start to finish. He agreed, and I got a backstage pass while he rehearsed the climb of his life.