Almost immediately he could hear the throbbing sound of a chopper.

Damn. “We’ve got to keep moving,” he said.

Alida stretched herself out on the grass, her filthy blond hair in tangles around her face, her once-white shirt the color of a dirty mouse, even the bloodstains obscured by dust. “Just give me a moment to catch my breath,” she said.

Warren Chu sat at his desk, sweating profusely and wishing the whole thing would be over. The FBI agent paced in the small office like a caged lion, occasionally asking a question before settling back into yet another long, excruciating silence. The rest of the Feds and security agents had disappeared into the tunnels; at first he’d heard a fusillade of shots, then the noises had grown increasingly muffled and distant before ultimately fading to silence. But this agent, the one named Fordyce, had stayed behind. Chu shifted, trying to unstick his sweating buttocks from the faux-leather chair. The A/C in this billion-dollar facility was, as usual, barely adequate. Chu was aware his comportment during the hostage situation had not exactly been heroic, and that added to his uneasy feeling. He consoled himself with the thought that he was still alive.

Fordyce wheeled around yet again. “So Crew said that? Exactly that? That somebody hacked into his computer while he was on vacation?”

“I don’t remember exactly what he said. Someone had it in for him, he said.”

Pace, turn. “And he claimed the emails had been planted?”

“That’s right.”

The FBI agent slowed. “Is there any way they could have been planted?”

“Absolutely no way. This is a physically isolated network. It isn’t connected to the outside world.”

“Why not?”

Chu was taken aback by the question. “Some of the most sensitive information in the country is in this system.”

“I see. So there’s no way those emails could have been planted by someone on the outside.”

“No way.”

“Could someone on the inside plant them? Like, for example, could you have planted them?”

A silence. “Well,” said Chu, “it wouldn’t be impossible.”

Fordyce stopped pacing, stared at him. “How would one go about it?”

Chu shrugged. “I’m one of the security administrators. In a highly classified network like this, somebody’s got to have full access. To make sure everything’s kosher, see. It would have taken a high level of technical skill—which I have. Of course, I didn’t do it,” he added hastily.

“You and who else could have done this—theoretically?”

“Me, two other security officers at my level, and our supervisor.”

“Who’s your supervisor?”

“Bill Novak.” Chu swallowed. “But look, all four of us have gone through stringent background checks and security reviews. And they’re watching us all the time. They’ve got access to everything in our personal lives: our bank accounts, travel, credit card statements, phone bills, you name it. As a practical matter, we’ve got no privacy. So for one of us to be involved in a terrorist plot—it’s just inconceivable.”

“Right.” Fordyce resumed pacing. “Did you know Crew well?”

“Pretty well.”

“You’re surprised?”

“Totally. But then, I knew Chalker, too, and I was floored when I heard about him. You never can tell. Both of them were a little off-kilter as human beings, if you know what I mean.”

Fordyce nodded and repeated, as if to himself, “You never can tell.”

There was a noise in the hallway, then the door burst open and a few of the security officers came back in, coated in dust, sweat beading their temples, bringing with them a smell of earth and mold.

“What’s going on?” Fordyce asked.

“They escaped, sir,” said the one Chu assumed was the team leader. “Into the side canyons leading down to the river.”

“I want the choppers deployed over the canyons,” Fordyce said. “Especially those with infrared capability. I want men deployed along the river, with teams going up every single one of those side canyons. And get me up in a bird, pronto.”

“Yes, sir.”

Fordyce turned back to Chu. “You stay here. I may have more questions for you.” And he was gone.

As Gideon and Alida bulled their way through the brush down the narrow canyon, the air above filled with choppers, the thwap of their rotors echoing up and down the stone walls, along with the drone of small planes and, perhaps, unmanned aerial vehicles. Spotlights flashed downward through the dusty air, columns of light roaming over the canyon walls. But the narrow canyons were choked with brush, with many overhanging rocks and alcoves, and so far they had found ample places to hide as the aircraft passed overhead.

Their progress was slow, interrupted frequently by the need to press themselves against the rock walls or cram under brush as spotlights passed them by. It was a warm night. Even though it was well after midnight, the rocks still held some heat of the intense sun, but the temperature was dropping fast. Gideon knew that, as the environment cooled, their presence would begin to show up better in the infrared sensing devices their pursuers had surely deployed.

Slowly they worked their way down toward the river.

A chopper suddenly passed very close overhead, its backwash whipping the bushes and raising furious clouds of dust. As the spotlight swept toward them, Gideon pushed Alida flat against the canyon wall. The blinding light passed over, then wobbled and came back, the chopper banking hard. The light fixed on them.

“Oh, shit,” he muttered.

No point in hiding now. Gideon pulled Alida along and they scrambled down the canyon while the chopper went into a hover, the light following them. They climbed over fallen rocks, slid down pour-overs. The canyon was dry, and it was hard to tell how far ahead the river lay.

More choppers appeared, taking positions in the sky. “Cease moving,” a voice boomed over the rotor noise. “Raise your hands.”

Gideon slid over a boulder, helped Alida down. Ahead, the canyon plunged even more steeply.

“Halt! Or we fire!”

Gideon recognized Fordyce’s voice. He was furiously angry: this was personal.

They came to the edge of another pour-over. This time, the drop was some ten feet to a muddy pool.

“Your final warning!”

They jumped just as a burst of automatic weapons fire sounded, hurtled downward, and landed heavily in water-covered mud. They struggled up out of the pool and staggered into a thicket of salt cedars, gunfire ripping and shredding the branches around them and smacking into the rock walls on either side. The searchlights temporarily lost them, roving widely through the heavy vegetation.

They came to a final pour-over, with nothing but blackness below. The searchlights hit them again.

“Jump!” Gideon cried.

“But I can’t see a damn—”

“It’s either that or get shot. Jump!”

They jumped—a sickening, terrifying plunge into blackness—and then landed in icy whitewater. Gideon felt himself tumbling head over heels in the torrent, racing and thundering along. They had reached the rapids of the Rio Grande, boiling through White Rock Canyon.

“Alida!” he cried, thrashing around. He got a glimpse of a white face to his left. “Alida!” He tried to swim, the strong current sweeping them both downstream among roaring cataracts and huge standing waves.

“Gideon!” he heard her cry. He reached out, contacted her body, then grasped her hand. There was nothing to do but ride it out.

The choppers had spread out, the spotlights sweeping wildly across the river; apparently they had misjudged, because they were focusing on a stretch of the river upstream of them. The canyon was narrow and deep here, and rules of separation seemed to be limiting the number of helicopters, as only three now were taking part in the search.