To my niece, Tonya

A special thanks to my brother, Charlie, for information about knives; Dr. McDaniel; my husband; and my editor Martha Bushko.

Diane squirmed on her belly through the crack in the rock, dragging her backpack behind her on a tether. The crawl-way was no more than a slit, as if the cave wall had been pierced through with a giant knife blade. The passage was maybe twenty feet long, barely wider than her shoulders, the ceiling two feet high at its highest, sixteen inches at its lowest-a tight fit. Loose stones scraped through her clothes from her chest to her abdomen and down her back. Of all the places she could be, this was the best-the dark, secret places of a cave.

Despite the cool temperature, sweat dampened her shirt, making it cling to her skin. Her mouth was dry from breathing in dust, and she craved a sip of cool water from the bottle tied to her backpack. Her fingertips felt the edges of the opening at the end of the tight passage. She tugged and squirmed until her head emerged into a larger tunnel running sharply to the right. Diane slithered out of the crack like a cave creature, a small cascade of pebbles and dust following her out and down a gentle slope to where she had room to rise to her hands and knees.

The dual lamps on her helmet illuminated the walls, making round designs of light and shadows on the red-brown rock. Ahead, the height of the tunnel increased. At its end, about three feet above the floor, an irregular opening gaped like the mouth of a shark.

Diane slid into a sitting position, pulled her backpack to her and took a long drink from her water bottle. Her gaze briefly lingered on the distant hole in the wall before she examined the sides of the tunnel, picking out survey stations-line-of-sight points from which to measure direction and distance. This visit, she’d only mark the stations with small tags. She liked to go slow when she mapped a cave-do an open traverse and take only basic measurements the first trip, get a feel for the cave.