As you watch Ronnie Dickson spider his way along the underside of a rock overhang, it’s easy to think he’s a bit of a superhero. As he calmly picks his way across the pocked sandstone face, he seems to violate the laws of physics, thumbing his nose at gravity. It’s not until he muscles up a vertical slab that you see the effort he’s putting out. Most climbers try to always keep three balance points—hands or feet, usually—on the wall, supporting their weight as they extend a fourth point toward the next hold. Dickson doesn’t have a fourth point. With his left leg missing above the knee, every time he reaches for a new hold with his right leg, he suspends his entire weight from his fingertips. If he wears a climbing prosthesis, it helps, but when he reaches for a new hold with a hand, he still has to race gravity, lunging ape-like across the stone, jamming his chalky fingers into cracks, concentrating for his life. Sometimes, he falls. When that happens, he returns to the face, climbs back up, and oftentimes plummets again. He climbs, then falls, again and again, until he solves the problem or he’s flat on his back on the crash pad, utterly spent for the day.