'Don't exhale in here,' Book said.

Big Rick stuck his head out the window and exhaled smoke.

'Aah.'

He pulled his head back inside and a big bag of Cheetos from his backpack. He stuffed Cheetos into his mouth then held the bag out; Book declined, but Carla shrugged and took a handful.

'I do like Cheetos.'

Book shook his head. 'Heck of a team. A law professor, an environmentalist with a grudge, and a stoned artist with a loaded weapon and a bag of Cheetos.'

'And ready to kick some a.s.s,' Big Rick said.

Carla pointed. 'Look.'

The tanker trucks carrying the flow-back fluid began exiting the site. They counted fifty trucks that turned north on 67, the road to the disposal wells in Pecos County. But fifty turned south on 67, the road to- 'Mexico,' Big Rick said.

After the final truck had pa.s.sed, Book started the engine and shifted into gear but did not turn on the lights. He turned south and followed the red taillights. Carla videotaped and narrated. Big Rick smoked pot. Highway 67 turned east and led them through Alpine and toward Marfa. In the distant sky to the south lightning strikes flashed above the mountains. The faint sound of thunder broke the silence of the night.

'Desert storm over Mexico,' Carla said. 'It'll lightning and thunder, but it never rains.'

They pa.s.sed through Alpine; the streets sat vacant.

'Can we stop and get some potato chips?' Big Rick asked.

'No.'

They cleared the town and wound through the Chisos Mountains then descended onto the Marfa Plateau. Eight miles further, just before the Marfa Mystery Lights Viewing Center, the trucks abruptly turned south on an unmarked dirt road that cut through the desert.

Deputy Shirley liked to come out to the viewing center late at night when she worked the midnight shift. The center was an open rock structure with a cement floor and a low rock wall; people gathered at night in hopes of seeing the mystery lights. But not at three-thirty in the morning. That's when she liked to come out; not to watch the mystery lights, but to screw on the low rock wall under the stars. And tonight the distant lightning made the moment even more romantic. She wore her uniform shirt with the Presidio County Sheriff's Department badge and her leather holster, but her uniform trousers lay on the cement floor. She sat bare-bottomed on the wall with her legs up high and spread for the cowboy named Cody; he was working hard and doing a very good job. The night was cool, but her thick white boot socks and Cowboy Cody's body heat kept her toasty. Shirley felt the heat building down below, and her body began rumbling- -but not with the throes of an o.r.g.a.s.m. The rumbling came from the line of tanker trucks barreling past not a hundred feet away down the Old Army Air Field Road. Cowboy Cody continued his hard work as she watched the tankers-ten, twenty, thirty ... must be fifty trucks-heading deep into the dark desert. Odd. But then, sculptures made out of crushed cars were pretty odd, too. She turned back to Cody and tried to get her mind and body refocused on the moment before he ran out of gas when another vehicle turned off Highway 67 and headed down the dirt road into the desert. It was a pickup truck, a familiar-looking one, with a driver she recognized in the flash of the next lightning strike: the professor. He was driving with no headlights.

'What the h.e.l.l?'

Cowboy Cody panted hard.

'Sorry. I held it as long as I could.'

'Not you. The trucks.'

Cowboy Cody backed away to police himself-Shirley insisted her beaus practice safe s.e.x-and she drew the cell phone from her holster.

Presidio County Sheriff Brady Munn slept peacefully in his bed next to his wife of twenty-seven years. With the kids grown and gone, there were no more sleeps interrupted for bottle duty or diaper duty or chaperone duty; and Presidio County was not exactly a hotbed of criminal activity. Consequently, he was startled awake by the ringing phone. He reached out, found the phone, and put the receiver to his ear.

'This better be good.'

'It is.'

Shirley.

'What time is it?'

'Three-thirty.'

His niece told him what she had just witnessed out by the viewing center.

'G.o.dd.a.m.n amateurs. They're gonna get themselves killed playing detective. He can't kung fu the cartels. What the h.e.l.l are you doing out there, anyway?'

'Keeping Presidio County safe.'

'Well, put your pants on and get the h.e.l.l back to town.'

She giggled and disconnected. He replaced the receiver and rubbed his face. Relatives. If it was just the tankers, he'd call Border Patrol and let them handle the situation. But Carla and the professor made him sit up and say to his wife, 'Honey, I'm gonna run down to the border,' like many a husband might say he was running to the neighborhood convenience store. She grunted and rolled over.

They drove over old runways.

'They're taking a shortcut through the old Marfa Army Air Field,' Carla said. 'Skirting town, to avoid a curious Border Patrol agent wondering what all these trucks are doing heading toward Mexico in the middle of the night. They'll pick up the highway again south of town.'

Rumbles of thunder rolled over the Marfa Plateau. Book's cell phone rang. He answered.

'Hi. I couldn't sleep. Alone.'

Carmen Castro.

'Uh, Carmen, I'm going to have to call you back. I'm right in the middle of something.'

'Does it involve a woman?'

'It's not quite that dangerous.'

Carmen sighed. 'You said you were coming back.'

'I've been delayed.'

'I've gone to the gun range every night, to get over my s.e.xual frustrations.'

'Well, uh, whatever works.'

'It's getting expensive. I've gone through two thousand rounds of ammo. You want to have phone s.e.x?'

'Uh, not a good time.'

A groan from Carmen. 'Call me.'

Book disconnected.

'Carmen?' Carla said.

'How old is she?' Big Rick said.

'Can we focus here?'

Big Rick took a long drag on his joint then hung his head out the window.

Border Patrol Agent Wesley Crum chased the wets into the desert just off Highway 67 about forty miles south of Marfa and twenty miles north of the border. Through the night-vision goggles, he counted five males and five females. No doubt a family reunion. An odd sound broke the silence of the night and caused him to stop and turn back to the highway. He observed an equally odd sight: a long line of tanker trucks heading south like ducks migrating for the winter. Only it was late spring, so they should be migrating north. The ducks, not the tanker trucks.

'Where the h.e.l.l are they going?'

'Come on,' Angel said, 'let's get these folks.'

'You're always wanting to let them go. Tonight you want to chase them? Look.'

Wesley pointed, and Angel turned and looked. A ways behind the last tanker truck, a pickup truck followed with its lights off. But with the goggles, Wesley recognized the big potato embedded on the antenna.

'I know that potato. That's Carla's truck. And the professor. Maybe he ain't a good guy after all. Let's find out.'

'Come on, Wesley, let's take care of these people.'

Just then another pickup truck with its lights off pa.s.sed. It was following Carla's truck.

'Who the h.e.l.l is that? Come on, Angel, they're up to something, and at four in the morning, it ain't no good.'

'They're just tanker trucks, Wesley. Going south, not north. They're not smuggling dope into Mexico. Let's do our job.'

'I am.'

Wesley took off running toward the highway and their Border Patrol SUV parked off the road. Angel shook his head then dropped the jug of water he was carrying and yelled to the Mexicans in the desert.

'Agua! Agua!'

Angel Acosta ran after Wesley Crum.

Twenty minutes later, just outside the town of Presidio, the tankers turned west on Farm-to-Market 170, the river road. Book steered the pickup after them. The Rio Grande was visible to their left in the illumination of the lightning strikes, which came more often now.

'I'm hungry,' Big Rick said. 'You kids hungry?'

'They're going to cross the river,' Carla said.

'How?' Book said. 'The river's full.'

'The Rio Conchos from Mexico joins up just a few miles upriver. Beyond that, the riverbed is dry because of all the dams upstream of El Paso. If not for Mexican water in the Conchos, the Rio Grande would be dry all the way to the Gulf of Mexico.'

'I know an all-night cafe in Presidio,' Big Rick said. 'We could stop off and-'

Book looked over at Big Rick and put a finger to his lips.

'Shh.'

Border Patrol Agent Wesley Crum drove the SUV. The tanker trucks were leading this caravan south. Carla and the professor were following the tankers with their lights out. The second pickup truck was following Carla and the professor with its lights out. Wesley and Angel were following the whole G.o.dd.a.m.ned bunch of them with their lights out. And Wesley was thinking, Who are the good guys and who are the bad guys? On the border, it was often difficult to tell.

'Am I right, Angel?'

'Yeah, you're right.'

'I figure they're gonna head west on One-seventy, cross the river above the Conchos.'

'Looks that way.'

'We could hit the lights and siren, speed to the front of the line, and try to stop the tankers.'

'That would be one option. How many guns we got?'

'Not enough.'

'Exactly.'

'So we follow?'

'We follow.'

Chapter 35.

Six hundred miles southeast of Presidio in the Predator Ops command center on the second floor of an airplane hangar at the Corpus Christi Naval Air Station, U.S. Customs and Border Protection Air Interdiction Agent Dwight Ford watched the live video feed from the infrared camera aboard the Predator B drone as the unmanned aircraft banked left and right with the course of the Rio Grande. The drone's camera gave them 'eyes in the sky' above the 1,254-mile MexicoTexas border. The images on the flat screen were sharp; from twenty thousand feet up, the camera could identify vehicles and humans, but not faces. But all it was identifying at the moment was the bare desert on either side of the river.

Dwight 'liaised'-a word he had never even heard before he was a.s.signed to the drone-between the drone pilots and the Border Patrol agents on the ground. They had gotten a call-in tip that a big drug shipment was coming across the river below Nuevo Laredo, so the Predator had flown over that location most of the night; but it turned out to be another bulls.h.i.t call. Dwight figured it might be a decoy, so he had the pilot fly the drone west of Nuevo Laredo. They found no activity, so they flew further west. They were now over Presidio.

Dwight wore his military-style tan jumpsuit and brown cap. He was leaned back in his captain's chair, and his feet were kicked up on the desk where the computers and keyboards and phones were situated; his hands were clasped behind his head. He glanced up at the black digital strip on the wall showing military times in red numerals: Pacific, 02:31 ... Costa Rica, 03:31 ... Panama, 04:31 ... Eastern, 05:31 ... Zulu, 09:31 ... Local, 04:31. He was having a h.e.l.l of a time keeping his eyes open.

'Dwight-wake up!'

Dwight snapped forward in his chair. The drone pilot was on the radio. Dwight clicked on his radio headset that connected him to the flight trailer parked outside where Lance and Grady, the pilot and co-pilot, flew the drone with a joystick like the kind his sons used to play their video games.

'What?'

'Look.'

On the screen were images of tanker trucks, a long line of tanker trucks. He checked the other flat screen displaying a Google Earth map that tracked the drone's path.

'They're driving west on FM One-seventy,' Lance the drone pilot said.

The drone had cleared Presidio and now flew west over the river road past the point where the big Rio Conchos flowed into the Rio Grande. The trucks seemed to be slowing-yes, they were definitely slowing-and turning south. The line of trucks drove across the dry riverbed and crossed into Mexico as if they were UPS trucks making deliveries in the neighborhood. But what were those tanker trucks delivering to Mexico?