They understood nothing. That was not claustrophobia. That was logic, survival instinct, an IQ test. Anna sniffed, an exclamation remarkably close to "harumph."

Lisa looked up with limpid gray eyes, the tails of her braids brushing Anna's boot tops. "Too tight?" she asked, and reached to adjust the buckle that cinched the webbing around Anna's upper thigh and under her buttock.

"No," Anna said, and, with an effort, "Sorry."

Again the acceptance. Again the total lack of understanding. Apparently idiosyncratic behaviors were not cause for comment in the caving community.

"You'll want it tight," Timmy said. "Once you get your weight on it things loosen up considerably."

Anna knew that. But for the pack, the gear was familiar. Climbing equipment: seat and chest harness, locking carabiners, rappel rack, Gibbs ascenders, D-ring, JUMAR safety. All the chunks of metal and rope intended to keep a caver in one piece on the way down and on the way back up. From a lifetime's habit of safety, Anna watched as each link was forged in the chain of devices designed to defy gravity.

Letting Timmy and Lisa tell her things she knew, dress her as if she were a baby, she contributed little. Much of her brain was given over to a jumble of dangerous thoughts, dangerous because a preoccupied climber can very easily become a dead climber. A moment's inattention, an unclosed D-ring, an improperly threaded rack, an unlocked carabiner, and suddenly the whole house of cards-and the climber- comes tumbling down.

Anna longed to call her sister, Molly, to talk about friendship and irrational fears, duty and human frailty. Since there was no time for a chat with her personal shrink, she went through her mental files and pulled out everything she could remember her sister having said about coping with phobic reactions. Desensitization, the slow increasing of exposure to the feared situation; no time. Relaxation exercises. Anna snorted, and Lisa and Timmy stopped what they were doing to look at her expectantly.

"It's good," Anna said. "Perfect. Thanks." Lisa beamed her transforming smile. The gear was hers, lent to Anna for the duration. Anna smiled back, appreciating the woman's generosity. By rights Lisa should be the one going in. She was a strong and experienced caver. She hadn't been to Tinker's Hell, the part of Lechuguilla where Frieda had been injured, but she'd been on three survey expeditions into the cave, trips of five days each. Anna knew that at times of high drama, along with concern for the injured and the desire to be of help, there was an overpowering need to be a part of the adventure. In a way she'd cheated Lisa out of that.

"Climbing I'm comfortable with," Anna said. "Let's go over the rest of it."

The three of them were in a largish room outside the chief of resource management's office in a building down the hill from Oscar's office. It was of the same soft-hued native stone as the other buildings. The inside was clean and open with a beautiful old fireplace filling one wall. The grate was cold, seldom, if ever, used. The air was warmed to a uniform seventy degrees by modern methods. Anna would have welcomed the comfort of living fire. Through the window, opening onto stairs leading up the hill to the other buildings, Anna could see that a thin drizzle had started. Cold, gray, winter rain, falling on concrete. Soft, lifeless rain. Ray Bradbury rain.

Drama queen, Anna cursed herself, and turned abruptly to the pile of debris on the chief's blond wood conference table, the guts of her sidepack waiting to be inventoried.

"How much do you know?" Timmy asked.

"Pretend I don't know anything and you'll be pretty close," Anna said.

His manner might have warmed a degree or two. Her admission of total ignorance took him off guard. "Okay," he said. "We'll start from the beginning." His thin voice took on a pedantic drone, and Anna felt a vague stab of pity for all the Stanford undergrads sitting through whatever classes fledgling rocket scientists were required to sit through.

"Three sources of light," he intoned. "Light is more important than food or water. Your headlamp." He pointed with a long pale digit that looked well suited to a creature living deep underground. He waited. Apparently he wouldn't continue the lecture without classroom participation, so Anna nodded obediently.

"With spare batteries and bulbs. A flashlight." He pointed to a neat blue Maglite, brand-new and jewel-toned. "And what's your third source?" The tinted lenses winked at Anna, and she wondered if she should raise her hand before speaking.

"A candle?" she ventured, thinking of Tom Sawyer and Becky Thatcher.

That was the wrong answer Timmy had been fishing for. "Anachronism," he said triumphantly. "A candle in Lechuguilla is akin to a firefly in a whale's gullet, charming but not illuminating."

"We carried candles for years," Lisa volunteered. "When we switched out we noticed neither one of us had thought to bring matches." She laughed, a high whiffling sound. Her husband was not amused.

"Third source: another flashlight. More batteries." He stowed the lot away in the bottom of the pack.

Anna picked up a wide-mouthed plastic bottle from the pile. The top was a white screw-on cap with the letter "P" written on it with a Sharpie permanent marker. "What's this?"

"Just what it says," Timmy replied. "You pack it in, you pack it out."

"There's one urine dump near the permanent camp on the way out," Lisa added helpfully. "If you need to you can dump it there."

"Don't use it," Timmy said. "Pack it out."

From her brief exposure to caving literature, Anna half remembered discussions on how the salts and sugars of human wastewater could, over time, alter the cave environment significantly. A filtering system to remove these components from the waste so only pure water would be left behind was in the works but was yet to be realized.

"Number two," Lisa said.

Anna's mind snapped back to the lesson at hand. Evidently she had missed number one.

"Feces," Timmy said succinctly. Anna had not missed number one. He held up a pile of zipper plastic bags. "In the bag. Zip it. Double bag. Zip it." Fleetingly Anna thought this would make a heck of a commercial for Gladlock green-seal bags. "Wrap it all in tinfoil. Pack it out."

"Burrito bags," Lisa said, and Anna detected a hint of mischief in the guileless eyes.

Caving, deep, serious caving, was beginning to take on the trappings of an expedition into outer space.

Things moved quickly, and for that Anna was grateful. This was not a time she would welcome interludes for deep introspection. Shortly before four p.m. Oscar Iverson and a man he introduced as Holden Tillman picked her and her gear up at the resource management office. She was unceremoniously stuffed into the back of a covered pickup truck along with packs, ropes, helmets, and other assorted paraphernalia. She would have preferred the distraction of conversation to being left alone with her thoughts. That option denied, she stared resolutely out through the scratched Plexiglas over the tailgate.

The ceiling of clouds had fractured. An ever-widening strip of blue pried open by the last rays of the sun shone on the western horizon. Rain and the season had leached the desert of color, leaving a palette of gray to be painted by the sunset. Drops of water clinging to the catclaw and sotol soaked up the light and refracted it in glittering facets of gold. The stones and black-fingered brush dripped with molten finery. Faint rainbows bent over the desert, where rain still fell through veils of light.

Anna mocked herself for feeling like a woman in a tumbrel, jouncing through her last glorious moments toward the guillotine and the vast unknown. Still, she rather wished the day had closed without this final hurrah of heavenly fireworks. A sunless world would have been that much easier to leave behind.