“Or get gas?”

“No, too open,” she said. “A restaurant parking lot full of cars would leave the killer less exposed. When you talk to Detective Kronewald, you’re going to suggest-” She held up one finger in the air to stress this word. “Suggest that Kronewald does a credit-card trace to find that restaurant. He’ll want to get somebody out there to search the parking lot for the discarded battery. It might have fingerprints. He would’ve done that anyway, but he’ll like that touch. I know this man. And he’ll like you, too. Tell him you’re driving all the way to Chicago to bring him a flat tire. The crime lab should find a tool mark on the air valve.”

He just stared at her in lieu of asking any more questions.

“The killer loosened the tire’s air valve,” she said. “Then he replaced the cap. He needed to disable the car, but he wanted it to stop down the road and away from witnesses. So the victim pulls over with a flat tire and checks it out with that little flashlight. He’s on a dark road, no lampposts. He can’t find any holes in his tire. Probably figures the problem is wear. The other three tires looked due for a change. And he couldn’t see much with that little flashlight of his. You’ve got the size of the broken bulb on your inventory?”

“Yes, ma’am. It’s a small one.”

“Close enough.”

“But won’t Detective Kronewald have to turn all of this over to the FBI?”

“He will-a piece at a time-every screwup Cadwaller made today, and Kronewald’s going to love every minute of it. Then he’ll probably solve the case for the feds. He’s a good detective.” She picked up her knapsack and rose from the table. “I’m out of here.”

“Wait, ma’am. Please? One more question? Why didn’t t he killer just steal Mr. Linden’s c e ll phone?”

“Good question,” said Mallory-with no sarcasm. “It helps if you know the murder weapon’s not a gun. It’s a sharp object. Kronewald wouldn’t like it if he knew I told you that.”

The trooper shook his head to say he would never betray her.

The lesson went on. “The killer went to a lot of trouble to remove that battery, and that was risky. He probably borrowed the phone from Linden, then told him it wasn’t working. That’s why Linden had it plugged into the car charger. He thought the battery was dead.”

“What about the tire? Why didn’t he just slash it? Or a puncture-a small hole for a slow leak. Why risk being seen fooling with that air valve?”

Mallory waited for the trooper to answer his own question. He had a good brain, and he must learn to use it.

The trooper nodded his understanding. “The killer wanted everything to look normal when Mr. Linden stopped on that road. If the phone was stolen-if the tire was slashed-”

Mallory was nodding, prompting him. “And don’t forget the caravan connection. The victim was on his way to join them. Gerald Linden already had murder on his mind. If he was suspicious, maybe scared-”

“The killer wouldn’t have gotten close enough to do him in-not without a fight.”

“That’s right.” Mallory was making her escape as she spoke-almost free. “So Linden’s out on a dark road with a flat tire, a weak flashlight and a dead cell phone. And suddenly-a dream come true.”

“Along comes a Good Samaritan-to kill him.”

“Now you’ve got it.” Her eye was on the clock; her hand was on the door. “And it was a familiar face. This was the man who borrowed his cell phone. Linden walked right up to his killer and shook the man’s hand.”

“Wait.” The trooper was rising from the booth as Mallory was backing out of the diner. “Where can I reach you?”

“You can’t. ”

The door closed on the New York detective, and the trooper settled back into the booth to gather up his notes and posters. He looked out the win- dow in time to see the silver convertible when it was only aiming at the road. A second later, a fly had found him. In the time it took to swat an insect, Mallory was gone. He could see over a fairly long stretch of open country, but he could not see her car. She had just traveled from zero miles per hour to gone.

This vanishing act was the only event of the day that did not have a clear explanation-considering the vehicle that she was driving-and it would color his permanent memory of her. Over the years to come, whenever he told his best story of old Route 66, he would not make Mallory any taller than she was, and even the size of her gun would remain the same. Nothing would need to be exaggerated.

Hours and miles west of the Illinois diner, one vehicle changed lanes to glide up alongside another, and now the encroaching driver was close enough to the Finns’ old Chevy to see the silhouette of a little girl in the back seat.

The six-year-old had been facing the other side of the family car when she turned suddenly to peer through her own window, as if she had felt a breath on the back of her neck. The watcher’s c ar dropped further behind and blended into the line of the caravan. Dodie Finn turned toward the front seat and a reassuring sight, the back of her father’s head. She rocked and hummed.

Her brother, Peter, rifled the glove compartment, then reached over his seat to pass her a stick of gum, asking, “Everything okay, Dodie?”

Inside she was screaming; outside she was smiling, unwrapping her gum.

“Seat belt,” said their father.

Peter obediently pulled back and disappeared with the click of the belt fastener.

Dodie hummed her little song; it quieted her heart, this same refrain, over and over-all that she could remember. She raised one small hand to rub the back of her neck, still sensing a touch of something nasty.

Charles Butler was wide awake, a great improvement over yesterday, when he had returned to New York from Europe after being marooned in one airport after another, missing planes for security searches and suffering massive sleep deprivation. Late this morning, he had awakened in the passenger seat of his Mercedes, wondering whither he was bound and what had possessed him to give the car keys to Riker, a man with no driver’s license. T r y as he might, Charles could not remember any conversation from the previous night, and thus he had traveled through the morning in the silent fog of the jet-lagged brain.

However, this afternoon he was rather enjoying himself, seated in this bright and lively restaurant. He was in the excellent company of two homicide detectives, who, between bites of steak and potato salad, discussed the bloody details of a recent murder.

So cheerful.

Detective Kronewald bore a slight resemblance to the late Louis Markowitz, particularly when the heavyset man gathered his hound-dog jowls into a brilliant smile. Riker seemed to like this Chicago policeman, and the oft-used phrase “you bastard” was apparently a term of endearment.

“Okay,” said Riker, “ I’ll tell you why Mallory turned you down cold. It’s the way you dole out information.” He leaned closer to the Chicago detective. “You think the kid doesn’t know you held out on her? She’s a bet- ter cop than I am, and fifteen minutes after I hit town, I found out about the other bodies.”

Riker paused a beat to accept the paperwork that would attach him and his absent partner to Chicago Homicide. “If you don’t give us everything, then I can’t talk Mallory into working this case.” He unfolded an Illinois map and laid it out on the table. “Now, if it’s not too much trouble-you bastard-just mark the places where the feds dug up the kids’ bodies.”

When Kronewald hesitated, Riker put a pen in the man’s hand, saying, “Mallory’s as good as they come, and you know that. By now, I promise you-these gravesites are all you got left to give away.”

“No, there’s more,” said their host, for this meal was compliments of the city. “I got it all with me.”