"Sachs," he muttered as she entered the room, "was it a big scene? Was it huge?"

"Not so big." She frowned at the question. "Why?"

His eyes were on the gray milk crates containing evidence she and several other officers carried. "I was just wondering because it seemed to take a long time to search the scene and get back here. It is okay for you to use that flashing light on your car. That's why they make them, you know. Sirens are allowed too." When Rhyme was bored he grew testy. Boredom was the biggest evil in his life.

Sachs, however, was impervious to his sourness – she seemed in a particularly good mood – and said merely, "We've got ourselves some mysteries here, Rhyme."

He recalled that Sellitto had used the word "bizarre" about the killing.

"Give me the scenario. What happened?"

Sachs offered a likely account of the events, culminating in the perp's escape from the recital hall.

"The respondings heard a shot inside the hall then they did a kick-in. Timed it together, went in through the only two doors in the room. He was gone."

Sellitto consulted his notes. "The patrol officers put him in his fifties, medium height, medium build, no distinguishings other than a beard, brown hair. There was a janitor who says he didn't see anybody go in or out of the room. But maybe he got witnessitis, you know. The school's gonna call with his name and number. I'll see if I can refresh his memory."

"What about the vic? What was the motive?"

Sachs said, "No sexual assault, no robbery."

Sellitto added, "Just talked to the Twins. She hasn't got any present or recent boyfriends. Nobody in the past that'd be a problem."

"She was a full-time student?" Rhyme asked. "Or did she work?"

"Full-time student, yeah. But apparently she did some performing on the side. They're finding out where."

Rhyme recruited his aide, Thom, to act as a scribe, as he often did, jotting down the evidence in his elegant handwriting on one of the large whiteboards in the lab. The aide took the marker and began to write.

There was a knock on the door and Thom disappeared momentarily from the lab.

"Incoming visitor!" he called from the hallway.

"Visitor?" Rhyme asked, hardly in the mood for company. The aide, though, was being playful. Into the room walked Mel Cooper, the slim, balding lab technician whom Rhyme, then-head of NYPD forensics, had met some years ago on a joint burglary/kidnapping case with an upstate New York police department. Cooper had disputed Rhyme's analysis of a particular type of soil and had been right, it turned out. Impressed, Rhyme had dug into the tech's credentials and found that, like Rhyme, he was an active and highly respected member of the International Association for Identification – experts at identifying individuals from friction ridges, DNA, forensic reconstruction and dental remains. With degrees in math, physics and organic chemistry, Cooper was also top-notch at physical-evidence analysis.

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.

"Can you source any of it?" Sellitto asked.

"Generic fuse – untraceable – and the squib's destroyed. No manufacturer, nothing."

Cooper shook his head. All that was left, Rhyme could see, were tiny shreds of paper with a burned metal core of fuse attached. The strings turned out to be narrow-gauge 100-percent cotton, generic and thus also impossible to source.

"There was that flash too," Sachs said, looking over her notes. "When the officers saw him with the victim he held up his hand and there was a brilliant light. Like a flare. It blinded both of them."

"Any trace?"

"None that I could find. They said it just dissolved in the air."

Okay, Lon, you said it: bizarre.

"Let's move on. Footprints?"

Cooper pulled up the NYPD database on shoe-tread prints, a digitized version of the hard-copy file Rhyme had compiled when he'd been head of NYPD forensics.

After a few minutes of perusal he said, "Shoes are slip-on black Ecco brand. Appear to be a size ten."

"Trace evidence?" Rhyme asked.

Sachs picked several plastic bags out of a milk crate. Inside were strips of adhesive tape, torn off the trace pick-up roller. "These're from where he walked and next to the body."

Cooper took the plastic bags and extracted the adhesive tape rectangles, one by one, over separate examining trays, to avoid cross-contamination. Most of the trace adhering to the squares was dust that matched Sachs's control samples, meaning that its source was neither the perp nor the victim but was found naturally at the crime scene. But on several of the pieces of tape were some fibers that Sachs had found only in places where the perp had walked or on objects that he'd touched.