"No," Rhyme said to her. "We still don't know for certain he's gone." Sellitto stood away from the glass as he drew the drapes shut.
Oddly, it was scarier not knowing exactly where the Dancer was than thinking he was pointing a large rifle through a window twenty feet away.
It was then that Cooper's phone rang. He took the call.
"Lincoln, it's the Bureau's bomb people. They've checked the Explosives Reference Collection. They say they've got a possible match on those bits of latex."
"What do they say?"
Cooper listened to the agent for a moment.
"No leads on the specific type of rubber, but they say it's not inconsistent with a material used in altimeter detonators. There's a latex balloon filled with air. It expands when the plane goes up because of the low pressure at higher altitudes, and at a certain height the balloon presses into a switch on the side of the bomb wall. Contact's completed. The bomb goes off."
"But this bomb was detonated by a timer."
"They're just telling me about the latex."
Rhyme looked at the plastic bags containing components of the bomb. His eyes fell to the timer, and he thought: Why's it in such perfect shape?
Because it had been mounted behind the overhanging lip of steel.
But the Dancer could have mounted it anywhere, pressed it into the plastic explosive itself, which would have reduced it to microscopic pieces. Leaving the timer intact had seemed careless at first. But now he wondered.
"Tell him that the plane exploded as it was descending," Sachs said.
Cooper relayed the comment, then listened. The tech reported, "He says it could just be a point-of-construction variation. As the plane climbs, the expanding balloon trips a switch that arms the bomb; when the plane descends the balloon shrinks and closes the circuit. That detonates it."
Rhyme whispered, "The timer's a fake! He mounted it behind the piece of metal so it wouldn't be destroyed. So we'd think it was a time bomb, not an altitude bomb. How high was Carney's plane when it exploded?"
Sellitto raced through the report. "It was just descending through five thousand feet."
"So it armed when they climbed through five thousand outside of Mamaroneck and detonated when he went below it near Chicago," Rhyme said.
"Why on descent?" the detective asked.
"So the plane would be farther away?" Sachs suggested.
"Right," Rhyme said. "It'd give the Dancer a better chance to get away from the airport before it blew."
"But," Cooper asked, "why go to all the trouble to fool us into thinking it was one kind of bomb and not another?"
Rhyme saw that Sachs figured it out just as fast as he did. "Oh, no!" she cried.
Sellitto still didn't get it. "What?"
"Because," she said, "the bomb squad was looking for a time bomb when they searched Percey's plane tonight. Listening for the timer."
"Which means," Rhyme spat out, "Percey and Bell've got an altitude bomb on board too."
"Sink rate twelve hundred feet per minute," Brad sang out.
Percey gentled the yoke of the Lear back slightly, slowing the descent. They passed through fifty-five hundred feet.
Then she heard it.
A strange chirping sound. She'd never heard any sound like it, not in a Lear 35A. It sounded like a warning buzzer of some kind, but distant. Percey scanned the panels but could see no red lights. It chirped again.
"Five three hundred feet," Brad called. "What's that noise?"