Not far above them, I sat in a large gallery, listening for their drills. The gallery was pristine; it had been discovered only days before, and I was one of the first ever to enter it. But where I sat, surrounded by towering stalagmites and colossal mushrooms of stone, the cavern was alive with other sounds. At my elbow, water tinkled into limpid basins, while overhead, thousands of swiftlets—tiny black birds that spend much of their lives in the pitch-black chambers—twittered and clicked and echolocated toward nests made of saliva, moss, and mud.

If Frank and Cookie were making history somewhere below my feet, I wasn't going to hear it. But that was fine. More than any other sport, caving is about secrets and the things we endure to find them out. Sometimes all you can do is wait to see what the darkness reveals. So I lay back, turned out my light, and listened as the swifts swooped low, coming so close I could feel wingbeats on my cheeks.