A road sign informed me that Casper, Wyoming, was 250 miles ahead. I set the Volvo's cruise control to make sure I stayed under the speed limit. When sunset approached and I put on my headlights, I felt even more inconspicuous, blending with thousands of other lights. I passed Cheyenne, Wyoming, able to distinguish little, except that its buildings seemed low and sprawling. Then, four hours after having left Denver, I approached the glow of Casper. For most of the drive, I'd sensed only flat land in the uninhabited darkness around me. Now the shadow of a mountain hulked on my left, blocking stars.

A few miles north of town, I saw a sign for the rest area. Traffic was sparse, most of the vehicles having driven into Casper. An arrow pointed toward a barely visible exit ramp. Following it off the interstate, I approached two squat brick buildings whose floodlights silhouetted three pickup trucks and a minivan.

But Petey would have needed more seclusion, so I took a gravel road that veered to the right from the pavement that led to the rest area. The floodlights at the buildings reached far enough to show picnic tables and stunted trees in back. Satisfying myself that no one had emerged from the rest rooms and seen what might have seemed unusual behavior, I reduced my headlights to parking lights and got just enough illumination to see a redwood-fenced area, behind which the tip of a Dumpster showed.

I parked behind the Dumpster, shut off my parking lights, and walked in front of the fence, verifying that no one, a state trooper, for example, had seen what I'd done and was coming to investigate. Confident that I was hidden, I unlocked the trunk.

What I imagined pushed me back. Kate and Jason on their sides. Squirming. Terrified. Duct tape pressed tightly across their mouths. Hands tied behind their backs. Ankles bound. Eyes so wide with fright that their whites were huge. Moans that were half apprehension, half pleas. The stench of bodily excretions, of carbon dioxide, of sweat and fear.

Petey would have taken off their gags and allowed them to catch their breath while he'd warned them not to scream. They'd have been too fear-weakened and groggy from the foul air in the trunk to manage much of an outburst. He'd have needed to lift them one at a time from the trunk, loosening their clothes so they could relieve themselves. That unpleasant intimacy would have tested his commitment to his new family. But his obligations were just beginning. For example, they'd have been terribly thirsty. Had he planned ahead and stopped at a fast-food place in Casper to get soft drinks, possibly french fries and hamburgers also? As he re-gagged them and put them back in the trunk, would he have said any reassuring words?

"I love you."

I shut the trunk. From the darkness behind the Dumpster, I stared toward the vehicles in front of the rest rooms. I walked in that direction, my footsteps crunching on pebbles. The floodlights at the two buildings made me feel naked the closer I came. By then, most of the vehicles had departed, leaving only a midsize sedan. I went into the men's room and found it empty. I stepped outside. Insects swarmed in the overhead light.

A woman left the other building, pulled keys from her purse, and approached the sedan. She didn't look in my direction. I imagined Petey starting to rush her, then pausing as headlights flashed past on the interstate, not a lot, but enough that there was never a gap, never a moment when somebody driving by wouldn't have seen a man attack a woman.

So Petey had waited for another opportunity, gone into the women's room, and subdued his victim there. He'd watched the interstate until there were just enough gaps between headlights that no one would see him in the few seconds that it took him to carry the unconscious woman around to the darkness. Behind the Dumpster, he'd tied and gagged her. Then he'd returned to the rest area, used the woman's key to start her car (a Caprice, the police had told me). He'd kept the headlights off and driven back to the darkness behind the fence, where he would have had to use a knife to make ventilation holes through the backseats into the Caprice's trunk before he transferred Kate and Jason into it.

But when he'd put the driver in the trunk with them, hadn't it worried him that there might not have been enough air for three people? Why had he risked suffocating Kate and Jason by putting the woman in the trunk with them? As it was, the woman had died. Why hadn't he killed her and hidden her body in the Dumpster? No one would have found her for quite a while, if ever. Again I felt Kate and Jason's horror as the asthmatic woman fought to breathe with the duct tape pressed over her mouth, her frenzied movements, her gagging sounds, her gradual stillness, the release of her bladder, probably her bowels. As the Caprice sped along the interstate, Kate and Jason would have been seized by the out-of-control fear that, if it had happened to the woman, it could happen to them.

The question kept nagging at me: Why hadn't Petey just killed her and hidden her body in the Dumpster? The only answer that made sense to me was that, no matter how indifferent Petey had felt toward the woman, he hadn't intended for her to die. Killing me was one thing. As far as Petey was concerned, I deserved to die for ruining his life. But this woman had merely happened to be in the wrong place at the wrong time. It was the first indication of humanity that I'd detected in him. It gave me hope for Kate and Jason.

He could have left the Volvo behind the Dumpster, where it might not have been discovered for days. Instead, he'd gone to the trouble of moving the Volvo to the front of the rest rooms, where it would be in plain sight. Because he wanted it to be found soon. He wanted it to point the way north, just as abandoning the Caprice outside Billings, Montana, made it seem that he was heading toward Butte. He'd been thinking with frightening control.

I drove back to the interstate. A road sign indicated that Billings, Montana, was 250 miles away. My eyelids felt heavy. But I had to keep moving. I had to complete Petey's escape.

Had he slept along the way? Doing that certainly tempted me. But I was afraid that if I steered off the interstate and found a secluded spot-a camping area, for example-where I could get a few hours' sleep, I wouldn't waken until daylight. In Petey's case, the Caprice might have been reported by then. He had to get to Billings. Imitating him, I kept driving.

I played the radio loud. In the middle of the night, it was hard to find a station. The ones I did find broadcast mostly evangelists riddled with static.

A mountain range stretched from north to south on my left. Moonlight glowed off the snowy peaks. My eyelids weakened. To stay awake, I bit my lips. I dug my fingernails into my palms. Interstate 25 became 90. I passed Sheridan, Wyoming, and entered Montana. The signs changed character: Lodge Grass; Custer Battlefield National Monument; Crow Agency… At Hardin, the interstate veered west. Meanwhile, as the miles accumulated, I imagined that Petey would have worried that his captives weren't getting enough air. He'd have stopped periodically on deserted roads to check on them. It pained me to think of Kate's and Jason's frightened eyes peering desperately up at him. They flinched when he reached in to touch their brows to calm them. As for the Caprice's driver, he barely looked at her.

When I finally read a sign for Billings, I was troubled that the distance between Casper and Billings should have taken me only four hours, but with frequent stops, pretending to check on my captives, I'd taken ninety minutes longer than I should have.

Even so, it was still dark when I came to the rest stop on the other side of Billings. A sign called it a scenic vista, but with the moon having set, I had only a vague sense of mountains to the north and south. Two vehicles were parked at the rest rooms: a pickup truck and a sedan. Here, too, a service road led behind the buildings. I parked in the darkness. Adrenaline overcame my exhaustion as I got out of the car. The air was surprisingly cold. Two men in cowboy hats came out of one of the concrete-block buildings. I waited while they got in the pickup truck and drove away. At this predawn hour, there was almost no traffic on the interstate. I walked quickly toward the rest rooms and listened for activity in either one. If I heard voices, if there was more than one person, I'd wait for a better opportunity. But if there was only one set of footsteps…