No down-home aphorisms, no done deals. Roland Bell, the man with two guns, nodded solemnly, his eyes moving quickly from shadow to shadow.

They had a mystery on their hands.

Cooper and Sachs had examined all the trace found in the treads of the Chicago fire trucks and police cars that had been at the scene of the Ed Carney crash. There was the useless dirt, dog shit, grass, oil, and garbage that Rhyme had expected to find. But they made one discovery that he felt was important.

He just didn’t have a clue what it meant.

The only batch of trace exhibiting indications of bomb residue were tiny fragments of a pliable beige substance. The gas chromatograph/mass spectrometer reported it was C₅H₈.

“Isoprene,” Cooper reflected.

“What’s that?” Sachs asked.

“Rubber,” Rhyme answered.

Cooper continued. “I’m also reading fatty acids. Dyes, talcum.”

“Any hardening agents?” Rhyme asked. “Clay? Magnesium carbonate? Zinc oxide?”

“None.”

“It’s soft rubber. Like latex.”

“And little fragments of rubber cement too,” Cooper added, peering at a sample in the compound microscope. “Bingo,” he said.

“Don’t tease, Mel,” Rhyme grumbled.

“Bits of soldering and tiny pieces of plastic embedded in the rubber. Circuit boards.”

“Part of the timer?” Sachs wondered aloud.

“No, that was intact,” Rhyme reminded.

He felt they were on to something here. If this was another part of the bomb, it might give them a clue as to the source of the explosive or another component.

“We have to know for sure whether this’s from the bomb or from the plane itself. Sachs, I want you to go up to the airport.”

“The—”

“Mamaroneck. Find Percey and have her give you samples of anything with latex, rubber, or circuit boards that would be in the belly of a plane like the one he was flying. Near the seat of the explosion. And, Mel, send the info off to the Bureau’s Explosives Reference Collection and check Army CID—maybe there’s a latex waterproof coating of some kind the army uses for explosives. Maybe we can trace it that way.”

Cooper began typing the request on his computer, but Rhyme noticed Sachs wasn’t pleased with her assignment.

“You want me to go talk to her?” she asked. “To Percey?”

“Yes. That’s what I’m saying.”

“Okay.” She sighed. “All right.”

“And don’t give her any crap like you’ve been doing. We need her cooperation.”

Rhyme didn’t have a clue why she pulled on her vest so angrily and stalked out the door without saying good-bye.

. . . Chapter Twenty-nine

Hour 31 of 45

At Mamaroneck Airport Amelia Sachs saw Roland Bell lurking outside the hangar. Another six officers stood guard around the huge building. She supposed there were snipers nearby too.

Her eye caught the hillock where she’d dropped to the ground under fire. She remembered, with a disgusted twist in her belly, the smell of the dirt mingling with the sweet cordite scent from her own impotent pistol shots.