Wriggling through a narrow chimney, knees and elbows thrust against the rock, she remembered a story she'd been told by a friend who led canoe trips for Outward Bound in the Boundary Waters of northern Minnesota. He'd taken a group of physically disabled people on a two-week trip. It wasn't a luxury vacation. Everybody did what they could, filling in the gaps for one another.

The story that stuck in Anna's mind was of a man who suffered from a crippling case of muscular dystrophy. In his late twenties, he'd been wheelchair bound over half his life. His greatest fear was that his house would catch fire. If he couldn't get to his wheelchair, he would burn to death.

During the trip this man was unable to carry canoes or gear on the many rough portages. But he chose not to be a burden to the others. He discovered an untapped talent. Clad in protective clothes, he crawled and inched and slithered, dragging his legs over fallen logs, across rocky beaches, and through weed-choked ravines.

By the end of his sojourn in the wilderness, his fear of burning to death in his own home was gone. "I can crawl out," he said. "I never thought of it. Shoot, I could crawl the six miles to the fire station if I had to." He'd regained some of his lost mobility.

The guy would have made a heck of a caver.

They'd been traveling ninety minutes, had gone less than three quarters of a mile, and had ventured into the earth four hundred feet, when they came to the North Rift.

The rift was a great crack running northwest to southeast, splitting the known world of the cave as a cleaver might halve a melon. Pointing with his light, Oscar picked out a hand line, threaded his rack, and descended. At the T-shaped junction where passage met rift, the cut was only fifteen feet deep. Moments later he was climbing up the far side. A cringing, spine-scraping crawl later they emerged next to a huge fissure. The Rift gone mad.