Marek looked up and saw Kate on the rim. "Hey," he said. "I've been looking for you. Get down here."

She scrambled down the ladder to the earthen floor of the pit. In the hot midafternoon sun, she smelled dirt, and the faint odor of organic decay. One of the skulls broke free and rolled to the ground at her feet. But she didn't touch it; she knew the remains should stay as they were until Chang removed them.

"This may be the catacombs," Kate said, "but these bones weren't stored. Was there ever a battle here?"

Marek shrugged. "There were battles everywhere. I'm more interested in that." He pointed ahead to the arch, which was without decoration, rounded and slightly flattened.

Kate said, "Cistercian, could even be twelfth century…"

"Okay, sure. But what about that?" Directly beneath the central curve of the arch, the collapse of the trench had left a black opening about three feet wide.

She said, "What are you thinking?"

"I'm thinking we better get in there. Right away."

"Why?" she said. "What's the hurry?"

Chang said to her, "It looks like there's space beyond the opening. A room, maybe several rooms."

"So?"

"Now it's exposed to the air. For the first time in maybe six hundred years."

Marek said, "And air has oxygen."

"You think there's artifacts in there?"

"I don't know what's in there," Marek said. "But you could have considerable damage within a few hours." He turned to Chang. "Have we got a snake?"

"No, it's in Toulouse, being repaired." The snake was a fiber optic cable that could be hooked to a camera. They used it to view otherwise inaccessible spaces.

Kate said, "Why don't you just pump the room full of nitrogen?" Nitrogen was an inert gas, heavier than air. If they pumped it through the opening, it would fill the space up, like water. And protect any artifacts from the corrosive effects of oxygen.

"I would," Marek said, "if I had enough gas. The biggest cylinder we've got is fifty liters."

That wasn't enough.

She pointed to the skulls. "I know, but if you do anything now, you'll disturb-"

"I wouldn't worry about these skeletons," Chang said. "They've already been moved out of position. And they look like they were mass-graved, after a battle. But there isn't that much we can learn from them." He turned and looked up. "Chris, who's got the reflector?"

Up above, Chris said, "Not me. I think they were last used here."

One of the students said, "No, it's over by grid three."

"Let's get it. Elsie, are you about finished with your pictures?"

"Pushy, pushy."

"Are you, or not?"

"One minute more."

Chang was calling to the students above, telling them to bring the reflectors. Four of them ran off excitedly.

Marek was saying to the others, "Okay, you people, I want flashlights, I want excavation packs, portable oxygen, filter headsets, lead lines, the works - now."

Through the excitement, Kate continued to eye the opening beneath the arch. The arch itself looked weak to her, the stones held loosely together. Normally, an arch kept its shape by the weight of the walls pressing in on the center stone, the keystone of the arch. But here, the whole upper curve above the opening could just collapse. The landslide of earth underneath the opening was loose. She watched pebbles break free and trickle down here and there. It didn't look good to her.

"André, I don't think it's safe to climb over that…"

"Who's talking about climbing over? We'll lower you from above."

"Me?"

"Yeah. You hang from above the arch, and then go inside." She must have looked stricken, because he grinned. "Don't worry, I'll go with you."

"You realize, if we're wrong

…" She was thinking, We could be buried alive.

"What's this?" Marek said. "Losing your nerve?"

That was all he had to say.

Ten minutes later, she was hanging in midair by the edge of the exposed arch. She wore the excavation backpack, which was fitted with an oxygen bottle on the back and had two flashlights dangling like hand grenades from the waist straps. She had her filter headset pushed up on her forehead. Wires ran from the radio to a battery in her pocket. With so much equipment she felt clunky, uncomfortable. Marek stood above her, holding her safety line. And down in the pit, Rick and his students were watching her tensely.

She looked up at Marek. "Give me five." He released five feet of line, and she slid down until she was lightly touching the dirt mound. Little rivulets of earth trickled away beneath her feet. She eased herself forward.

"Three more."

She dropped to hands and knees, giving the mound her full weight. It held. But she looked up at the arch uneasily. The keystone was crumbling at the edges.

"Everything all right?" Marek called.

"Okay," she said. "I'll go in now."

She crawled back toward the gaping hole at the arch. She looked up at Marek, unhooked the flashlight. "I don't know if you can do this, André. The dirt may not support your weight."

"Very funny. You don't do this alone, Kate."

"Well, at least let me get in there first."

She flicked on her light, turned on her radio, pulled down her headset so she was breathing through filters, and crawled through the hole, into the blackness beyond.

The air was surprisingly cool. The yellow beam of her flashlight played on bare stone walls, a stone floor. Chang was right: this was open space beneath the monastery. And it seemed to continue for some distance, before dirt and collapsed rubble blocked the far passage. Somehow this chamber had not been filled with dirt like the others. She shone her light up at the roof, trying to see its condition. She couldn't really tell. Not great.

She crept forward on hands and knees, then began to descend, sliding a little, down the dirt toward the ground. Moments later, she was standing inside the catacombs.

"I'm here."

It was dark around her, and the air felt wet. There was a dank odor that was unpleasant, even through the filters. The filters took out bacteria and viruses. At most excavation sites, no one bothered with masks, but they were required here, because plague had come several times in the fourteenth century, killing a third of the population. Although one form of the epidemic was originally transmitted by infected rats, another form was transmitted through the air, through coughs and sneezes, and so anybody who went into an old, sealed space had to worry about-

She heard a clattering behind her. She saw Marek coming through the hole above. He began to slide, so he jumped to the ground. In the silence afterward, they heard the soft sounds of pebbles and earth, trickling down the mound.

"You realize," she said, "we could be buried alive in here."

"Always look on the bright side," Marek said. He moved forward, holding a big fluorescent light with reflectors. It illuminated a whole section of the room. Now that they could see clearly, the room appeared disappointingly bare. To the left was the stone sarcophagus of a knight; he was carved in relief on the lid, which had been removed. When they looked inside the sarcophagus, it was empty. Then there was a rough wooden table leaning against a wall. It was bare. An open corridor going down to their left, ending in a stone staircase, which led upward until it disappeared in a mound of dirt. More mounds of earth in this chamber, over to the right, blocking another passageway, another arch.

Marek sighed. "All this excitement… for nothing."

But Kate was still worried about the earth breaking free and coming into the room. It made her look closely at the earth mounds to the right.

And that was why she saw it.

"André," she said. "Come here."

It was an earth-colored protrusion, brown against the brown of the mound, but the surface had a faint sheen. She brushed it with her hand. It was oilcloth. She exposed a sharp corner. Oilcloth, wrapping something.