Korsak and Mick did not know each other. As Rizzoli introduced them by the glow of the van’s dome light, she saw that Korsak was staring at the CST’s earring and noticed his hesitation before he shook Mick’s hand. She could almost see the wheels turning in Korsak’s head. Earring. Weight lifter. Gotta be gay.

Mick began unloading his equipment. “I brought the new Mini Crimescope 400,” he said. “Four-hundred-watt arc lamp. Three times brighter than the old GE three-fifty watt. Most intense light source we ever worked with. This thing’s even brighter than five-hundred-watt Xenon.” He glanced at Korsak. “You mind carrying in the camera stuff?”

Before Korsak could respond, Mick thrust an aluminum case into the detective’s arms, then turned back to the van for more equipment. Korsak just stood there for a moment holding the camera case, wearing a look of disbelief. Then he stalked off toward the house.

By the time Rizzoli and Mick got to the front door with their various cases containing the Crimescope, power cords, and protective goggles, Korsak had turned on the lights inside the house and the door was ajar. They pulled on shoe covers and walked in.

As Rizzoli had done earlier that day, Mick paused in the entryway, staring up in awe at the soaring stairwell.

“There’s stained glass at the top,” said Rizzoli. “You should see it with the sun shining through.”

An irritated Korsak called out from the family room, “We getting down to business here, or what?”

Mick flashed Rizzoli a what an asshole look, and she shrugged. They headed down the hall.

“This is the room,” said Korsak. He was wearing a different shirt from the one he’d worn earlier that afternoon, but this shirt, too, was already blotted with sweat. He stood with his jaw jutting out, his feet planted wide apart, like an ill-tempered Captain Bligh on the deck of his ship. “We focus here, this area of the floor.”

The blood had lost none of its emotional impact. While Mick set up his equipment, plugging in the power cord, readying the camera and tripod, Rizzoli found her gaze drawn to the wall. No amount of scrubbing would completely erase that silent testimony to violence. The biochemical traces would always remain in a ghostly imprint.

But it was not blood they sought tonight. They were searching for something far more difficult to see, and for that, they required an alternate light source that was intense enough to reveal what was now invisible to the unaided eye.

Rizzoli knew that light was simply electromagnetic energy that moved in waves. Visible light, which the human eye can detect, had wavelengths between 400 and 700 nanometers. Shorter wavelengths, in the ultraviolet range, were not visible. But when UV light shines on a number of different natural and man-made substances, it sometimes excites electrons within those substances, releasing visible light in a process called fluorescence. UV light could reveal body fluids, bone fragments, hairs, and fibers. That’s why she had requested the Mini Crimescope. Under its UV lamp, a whole new array of evidence might become visible.

“We’re about ready here,” said Mick. “Now we need to get this room as dark as possible.” He looked at Korsak. “Can you start by turning off those hall lights, Detective Korsak?”

“Wait. What about goggles?” said Korsak. “That UV light’s gonna blast my eyes, right?”

“At the wavelengths I’m using, it won’t be all that harmful.”

“I’d like a pair, anyway.”

“They’re in that case. There’s goggles for everyone.”

Rizzoli said, “I’ll get the hall lights.” She walked out of the room and flipped the switches. When she returned, Korsak and Mick were still standing as far apart as possible, as though afraid of exchanging some communicable disease.

“So which areas are we focusing on?” said Mick.

“Let’s start at that end, where the victim was found,” said Rizzoli. “Move outward from there. The whole room.”

Mick glanced around. “You’ve got a beige area rug over there. It’s probably going to fluoresce. And that white couch is gonna light up under UV, too. I just want to warn you, it’ll be tough to spot anything against that background.” He glanced at Korsak, who was already wearing his goggles and now looked like some pathetic middle-aged loser trying to appear cool in wraparound sunglasses.

“Hit those room lights,” said Mick. “Let’s see how dark we can get it in here.”

Korsak flipped the switch, and the room dropped into darkness. Starlight shone in faintly through the large uncurtained windows, but there was no moon and the backyard’s thick trees blocked out the lights of neighboring houses.

“Not bad,” said Mick. “I can work with this. Better than some crime scenes, where I’ve had to crawl around under a blanket. You know, they’re developing imaging systems that can be used in daylight. One of these days, we won’t have to stumble around like blind men in the dark.”

“Can we cut to the chase and get started?” Korsak snapped.

“I just thought you’d be interested in some of this technology.”

“Some other time, okay?”

“Whatever,” said Mick, unruffled.

Rizzoli slipped on her goggles as the Crimescope’s blue light came on. The eerie glow of fluorescing shapes appeared like ghosts in the dark room, the rug and the couch bouncing back light as Mick had predicted. The blue light moved toward the opposite wall, where Dr. Yeager’s corpse had been sitting, and bright slivers glowed on the wall.

“Kind of pretty, isn’t it?” said Mick.

“What is that?” asked Korsak.

“Strands of hair, adhering to the blood.”

“Oh, yeah. That’s real pretty.”

“Shine it on the floor,” said Rizzoli. “That’s where it’ll be.”

Mick aimed the UV lens downward, and a new universe of revealed fibers and hairs glowed at their feet.

Trace evidence that the initial vacuuming by the CSU had left behind.

“The more intense the light source, the more intense the fluorescence,” said Mick as he scanned the floor. “That’s why this unit is so great. At four hundred watts, it’s bright enough to pick up everything. The FBI bought seventy-one of these babies. It’s so compact, you can bring it on a plane as a carry-on.”

“What are you, some techno freak?” said Korsak.

“I like cool gadgets. I was an engineering major.”

“You were?”

“Why do you sound so surprised?”

“I didn’t think guys like you were into that stuff.”

“Guys like me?”

“I mean, the earring and all. You know.”

Rizzoli sighed. “Open mouth, insert foot.”

“What?” said Korsak. “I’m not putting them down or anything. I just happen to notice that not many of them go into engineering. More like theater and the arts and stuff. I mean, that’s good. We need artists.”

“I went to U. Mass,” said Mick, refusing to take offense. He continued to scan the floor. “Electrical engineering.”

“Hey, electricians make good money.”

“Um, that’s not quite the same career.”

They were moving in an ever-widening circle, the UV light continuing to pick up the occasional fleck of hair, fibers, and other unidentifiable particles. Suddenly they moved into a startlingly bright field.

“The rug,” said Mick. “Whatever these fibers are, they’re fluorescing like crazy. Won’t be able to see much against this background.”

“Scan it anyway,” said Rizzoli.

“Coffee table’s in the way. Could you move it?”

Rizzoli reached down toward what appeared to her as only a geometric shadow against a fluorescing background of white. “Korsak, get the other end,” she said.

With the coffee table moved aside, the area rug was a bright oval pool that glowed bluish-white.

“How we gonna spot anything on that background?” said Korsak. “It’s like trying to see glass floating in water.”

“Glass doesn’t float,” said Mick.

“Oh, right. You’re the engineer. So what’s Mick short for, anyway? Mickey?”