Rhyme mounted a campaign to get the man to return to the city where he'd been born and he finally agreed. The soft-spoken forensic tech/champion ballroom dancer was based in the NYPD crime lab in Queens but he often worked with Rhyme when the criminalist was consulting on an active case.

Greetings all around and then Cooper shoved his thick, Harry Potter-style glasses high on his nose and squinted a critical eye at the crates of evidence like a chess player sizing up his opponent. "What do we have here?"

"'Mysteries,'" Rhyme said. "To use our Sachs's assessment. Mysteries."

"Well, let's see if we can't make them a little less mysterious."

Sellitto ran through the scenario of the killing for Cooper as he donned latex gloves and began looking over the bags and jars. Rhyme wheeled up close to him. "There." He nodded. "What's that?" He was gazing at the green circuit board with a speaker attached.

"The board I found in the recital hall," Sachs said. "No idea what it is. Only that the unsub put it there—I could tell by his footprints."

It looked like it'd come from a computer, which didn't surprise Rhyme; criminals have always been in the forefront of technological development. Bank robbers armed themselves with the famous 1911 Colt .45 semiautomatic pistols within days of their release even though it was illegal for anyone but the military to possess one. Radios, scrambled phones, machine guns, laser sights, GPS, cellular technology, surveillance equipment and computer encryption ended up in the arsenal of criminals often before they were added to law enforcers'.

Rhyme was the first to admit that some subjects were beyond his realm of expertise. Clues like computers, cell phones and this curious device—all of which he called "NASDAQ evidence"—he farmed out to the experts.

"Get it downtown. To Tobe Geller," he instructed.

The FBI had a talented young man in its New York computer crimes office. Geller had helped them in the past and Rhyme knew that if anyone could tell them what the device was and where it might've come from Geller could do it.

Sachs handed off the bag to Sellitto, who in turn gave it to a uniformed policeman for transport downtown. But aspiring sergeant Amelia Sachs stopped him. She made sure he filled out a chain-of-custody card, which documents everyone who's handled each piece of evidence from crime scene to trial. She checked the card carefully and sent him on his way.

"And how was the assessment exercise, Sachs?" Rhyme asked.

"Well," she said. A hesitation. "I think I nailed it."

Rhyme was surprised at this response. Amelia Sachs often had a difficult time accepting praise from others and hardly ever bestowed it on herself.

"I didn't doubt you would," he said.

"Sergeant Sachs," Lon Sellitto pondered. "Gotta good ring to it."

They turned next to the pyrotechnic items found at the music school: the fuses and the firecracker.

Sachs had figured out one mystery, at least. The killer, she explained, had leaned chairs backward on two legs, balancing them in that position with thin pieces of cotton string. He'd tied fuses to the middle of the strings and lit them. After a minute or so the flame in the fuses hit the strings and burned through them. The chairs tumbled to the floor, making it sound like the killer was still inside. He'd also lit a fuse that ultimately set off the squib they mistook for a gunshot.