Anna listened to the plans being rehashed by Holden and Oscar as they walked single file along a ridge above a dry creek bed, and she began to wonder what would undo her first: her fear of enclosed spaces or her fear of crowds. The sheer absurdity freed her mind, and for a time she was able to shut out the human murmurings and enjoy the hike.

They were on a plateau to the north of the gypsum plains that spread down into Texas. What vegetation managed to eke out a livelihood from the parched soil kept a low profile. Little had grown to greater than knee height, and there were barren spaces between plants. With the lifting of the clouds and the dazzling clarity of the rain-washed air, Anna could see to the edge of the world, or so it seemed, and the world was all high, clean desert, burnished with gold.

Even knowing she walked over limestone honeycombed with passages, she couldn't imagine a less likely place to find the entrance to a world-class cave. She pictured the plateau cut into thin sections and placed between sheets of glass like the ant farms she'd seen as a child. Beneath her feet, creeping through those twisting tunnels, were human beings.

"There it is." Oscar interrupted her musings. They'd walked down a slope and crossed the stone bottom of a wash to climb again. Ahead of them was more of the same: low hills dotted with desert shrubs and cactus. "See that green spot?" Iverson pointed to a cluster of stunted trees poking from a fold in the hills. "That's it."

Anna took his word for it.

Within a few minutes they'd reached the trees, and still she was none the wiser. Not until they climbed down four or five feet to where the oak trees had found soil to root could she see the entrance. Back in the rocks an opening maybe twenty feet wide, thirty long, and ringed by heavy overhanging brows of rock, showed darkly.

Over the years Anna had made any number of rappels from ten to two hundred ten feet.