Shan offered a small grin. At least amid all the tragedy there were two good things. Jakli was starting a new life with Marco's son. And Deacon would be under the full moon with his son, listening to their insect orchestra.

Suddenly the dog started barking. They looked back to see Akzu rise. He raised his hand straight up, then lowered it to the back of his head as if scratching it.

Kaju gasped. "It's the signal," the Tibetan said urgently. "Someone is coming. Someone he has to warn about."

"Shit!" the American spat. "Shit and double shit." He began fumbling in the pockets of his baggy pants as Kaju herded the boys toward the shadows inside the structure, away from the line of sight to Akzu, who stood waiting for someone now, facing the road. The Kazakh was staying on the dune deliberately, Shan realized, so the new arrivals would come to him, so they would be visible from the building. Jakli and Kaju quickly pulled the doors shut, leaving a crack a few inches wide to see through.

A moment later a man appeared at Akzu's side, shorter and wider than Akzu. As he began speaking to the headman, he turned toward the bowl and his uniform came into clear view.

"Bao!" Jakli cried.

"It's all right," Kaju said, though his voice had no confidence. "Akzu has a plan. He will say he is checking the path for the Brigade herds to move to winter pasture. Sometimes there is water near here. If there is, he can save a day by cutting across the sand. He only wants to help the Brigade now, he will say, because he will be an owner soon. Since there is no water here, he will ask Bao to look on his map for a better route. If Bao wants to help, Akzu will go with him. If not, Akzu will keep talking until they all drive away together. Then he will return in four hours. It is agreed."

But the words seemed to give little comfort to the boys or to Deacon, all of whom stood wearing grim expressions in the dim light. The American had something in his hand that he had pulled out of his pocket- a small battery light, the size of a pencil. He had strapped his pack to his back and stepped to the window.

Shan watched Bao with a cold intense stare, remembering their last encounter, remembering how Bao's slap had drawn blood. The man seemed like a dark planet that had captured Shan in its orbit. Who else was there, how many others waited behind the dune in a knob patrol car?

Shan turned. Jakli was in the shadows with the boys now, one arm around each of them, comforting them. What a land we live in, he thought, where ten-year-old boys not only know what Public Security is but know to be terrified of it. He looked from Jakli to Deacon, and somehow knew each was thinking the same thing. Bao could take them all and have enough glory to get noticed in the capital. Shan the fugitive. Deacon the illegal American. The orphan boys for whom there was a private bounty. Jakli, absent from her paroled job.

Suddenly Bao was pointing at the building.

"We've got to go," Deacon said, and he began lifting Batu through the window.

"Go?" Kaju croaked in a desperate tone. "There is no place to go."

"Sure there is," Deacon replied. "We're going to become invisible." The American dropped Batu outside and climbed out himself.

Bao began slowly walking down the dune. Akzu hesitated, then followed, waving an unfolded map in the air, as if asking Bao a question. It took less than ten seconds for Jakli, Jengzi, Shan, and Kaju to clear the window.

Deacon was thirty feet away, at the remains of one of the small sheds, tearing away the floorboards. The shed was out of Bao's line of sight, blocked by the garage, but for how long no one could know. By the time Shan got to it the American had removed three planks and lowered the boys into a shaft underneath. Jakli and Kaju dropped inside, then Deacon pushed Shan in and jumped down himself.

"What is-" Shan began, but Deacon shoved him hard, pushing him into a darkness at the north side of the six-foot shaft. "As far as you can go!" Deacon ordered in a hushed, urgent voice, then he reached up to replace the planks.

Not until the American finished and began moving toward the others with his light did Shan see that they were in a tunnel lined with stone, nearly four feet high and perhaps five feet wide. Jengzi was crying, held by Jakli at the front. Kaju was next with Batu.

"Okay," Deacon said from behind Shan. "Today's archaeology lesson is about to begin."

"Archaeology?" Kaju gasped. Shan could hear the Tibetan breathing hard, as if he couldn't get enough air.

"Thirty more feet and it'll be safe to talk," Deacon said in a loud whisper.

The bottom of the tunnel was coated with a layer of sand, under which were the same square-cut stones that lined the rest of the tunnel. Every eight feet, wooden timbers, many still with their bark, stretched across the width of the tunnel, supported by small posts. As the group inched along in the dim light from Deacon's pencil lamp, sand trickled down from between the stones overhead.

"The karez," Deacon said when they stopped. "The ancient irrigation tunnels from the mountains, built to carry the melt water, like at Sand Mountain."

"Still intact?" Shan asked.

"Sure. See for yourself. Runs for miles in places. Up around Turfan, they still use them for irrigation, like some of the old Roman aqueducts in Italy. We found a map at Sand Mountain. Seemed to indicate a tunnel here. I checked it out this morning."

"But it's impossible," Kaju said, still breathing hard. "It can't be stable. We'll be-" He stopped, and Shan looked up the tunnel. The teacher's eyes were on his students.

"There were portals, all along the way," Deacon said. "Access for maintenance, access for taking out water. Just like what we came through. Just got to find the next one and out we go. Like pikas from their den."

The builders of the aqueduct had done their job well. For long stretches the stone work still fitted so tightly that the karez appeared to have been swept clean. In places there were small, stagnant puddles, meaning, Deacon pointed out excitedly, that at times of high water, in the spring thaw, some water was still finding its way down the old tunnels.

Shan began to recognize a pattern in the tunnel supports as they moved slowly forward. Every fifth set of beams was thicker and carved with scrolls and the shapes of plants, the plants once kept alive by the karez. In the center of each of the heavier beams was a small dragon head, facing north, ready in defense should demons seek to invade by subterranean means. To the front he heard Jengzi make a whimpering sound, calling out that there were spiderwebs. Shan felt like whimpering himself. There was no danger of Bao discovering them now, only the much more real threat of disturbing the fragile walls. If the roof collapsed, there would be no rescue, only blackness and enough time for horror to take hold as the oxygen was exhausted.

He heard Jakli speak calming words. Khoshakhan, he heard her repeat, the calming word for lambs. Jengzi, in front of Shan, stopped whimpering. But as they paused the boy began to inch forward to be beside Kaju. Shan was about to warn him that there was no room for two abreast when the boy's foot pulled against one of the ancient posts. There was a sound not of cracking or splintering, but simply a dry crunching noise as the bottom of the post fell away. The dribble of sand above became a steady flow, creating a thin falling veil that quickly accumulated on the tunnel floor.

"Go!" Deacon shouted. Jengzi scrambled forward, followed by Kaju and Shan. A stone fell onto Shan's back as he passed through the spilling sand. Before he cleared the breach, a second stone fell onto his leg. He paused to see if Deacon needed help.