"Relax," I said. "It's not K2." "I wouldn't be that cocky if I were you," said my brother Liam. A few years ago, he and I decided to climb Carrauntoohil, and this was my constant refrain to him in the week leading up to our assault on the mountain. He'd been ringing me daily with tips and updates. Bring this kind of jacket, pack this kind of food, the weather is predicted to be such-and-such. "Relax. It's not K2," I repeated. We arrived at Cronin's Yard on a dull damp day in July. The weather did not bode well for our hopes to see the views from the summit. A bunch of other prospective climbers stood huddled in the drizzle. We were split into smaller groups, climbing parties you might say, and allocated guides. One of our guides was a fit and nimble retired guard in his early fifties. The other man to lead us to the top was a local with an in-depth knowledge of the terrain and a broad Kerry accent of the Healy-...