Who the hell was this perp?

The results from the chromatograph/spectrometer popped onto a computer screen. "Okay, I've got pure latex… and what's this?" he pondered. "Something the computer identifies as an alginate. Never heard of -"

"Teeth."

"What?" Cooper asked Rhyme.

"It's a powder you mix with water to make molds. Dentists use it for crowns and dental work. Maybe our doer'd just been to the dentist."

Cooper continued to examine the computer screen. "Then we have very minute traces of castor oil, propylene glycol, cetyl alcohol, mica, iron oxide, titanium dioxide, coal tar and some neutral pigments."

"Some of those're found in makeup," Rhyme said, recalling a case in which he'd placed a killer at the scene after the man wrote obscene messages on the victim's mirror with a touch-up stick, smears of which were found on his sleeve. Running the case, he'd made a study of cosmetics.

"Hers?" Cooper asked Sachs.

"No," the policewoman answered. "I took swabs of her skin. She wasn't wearing any."

"Well, put it on the board. We'll see if it means anything."

Turning to the rope, the murder weapon, Mel Cooper looked up from his slump over a porcelain examining board. "It's a white sheath of rope around a black core. They're both braided silk – real light and thin – which is why it doesn't look any thicker than a normal rope even though it's really two put together."

"What's the point of that? Does the core make it stronger?" Rhyme asked. "Easier to untie? Harder to untie? What?"

"No idea."

"It's getting mysteriouser," Sachs said with a dramatic flair that Rhyme would have found irritating if he hadn't agreed with her.

"Yup," he confirmed, disconcerted. "That's a new one to me. Let's keep going. I want something familiar, something we can use."

"And the knot?"

"Tied by an expert but I don't recognize it," Cooper said.

"Get a picture of it to the bureau. And… don't we know somebody at the Maritime Museum?"

"They've helped us with knots a few times," Sachs said. "I'll upload a picture to them too."

A call came in from Tobe Geller at the Computer Crimes Unit at New York 's FBI headquarters. "This is fun, Lincoln."

"Glad we're keeping you amused," Rhyme murmured. "Anything helpful you might be able to tell us about our toy?"

Geller, a curly-haired young man, was impervious to Rhyme's edge, especially since there was a computer product involved. "It's a digital audio recorder. Fascinating little thing. Your unsub recorded something on it, stored the sounds on a hard drive then programmed it to play back after some delay. We don't know what the sound was – he built in a wiping program so that it destroyed the data."

"It was his voice," Rhyme muttered. "When he said he had a hostage it was just a recording. Like the chairs. It was to make us think he was still in the room."

"That makes sense. It had a special speaker – small but excellent bass and mid-tone range. It'd mimic a human voice pretty well."

"There's nothing left on the disk?"

"Nope. Gone for good."

"Damn. I wanted a voiceprint."

"Sorry. It's gone."

Rhyme sighed in frustration and rolled back to the examination trays; it was left to Sachs to tell Geller how much they appreciated the help.

The team then examined the victim's wristwatch, which had been shattered for reasons none of them could figure out. It yielded no evidence except the time it was broken. Perps occasionally broke watches or clocks at crime scenes after they'd set them to the wrong time to mislead investigators. But this was stopped at close to the actual time of death. What should they make of that?

Mysteriouser…

As the aide wrote their observations on the whiteboard Rhyme looked over the bag containing the sign-in book. "The missing name in the book." He mused, "Nine people signed but there're only eight names in the log… I think we need an expert here." Rhyme ordered into the microphone, "Command, telephone. Call Kincaid comma Parker."

On the screen the display showed a 703 area code, Virginia, then the number being dialed.

A ring. A young girl's voice said, "Kincaid residence."

"Uhm, yes. Is Parker there? Your father, I mean."

"Who's calling?"

" Lincoln Rhyme. In New York."

"Hold on, please."

A moment later the laid-back voice of one of the country's preeminent document examiners came on the line. "Hey, Lincoln. Been a month or two, hasn't it?"

"Busy time," Rhyme offered. "And what're you up to, Parker?"

"Oh, getting into trouble. Nearly caused an international incident. The British Cultural Society in the District wanted me to authenticate a notebook of King Edward's they'd purchased from a private collector. Note the tense of the verb, Lincoln."

"They'd already paid for it."

"Six hundred thousand."

"Little pricey. They wanted it that badly?"

"Oh, it had some real nice juicy gossip about Churchill and Chamberlain. Well, not in that sense, of course."

"Of course not." As usual Rhyme tried to be patient with those from whom he was seeking gratuitous help.

"I looked it over and what could I do? I had to question it." The innocuous verb, from a respected document examiner like Kincaid, was synonymous with branding the diary a bad-ass forgery.

"Ah, they'll get over it," he continued. "Though, come to think of it, they haven't paid my bill yet… No, honey, we don't make the frosting till the cake cools… Because I said so."

A single father, Kincaid was the former head of the FBI's documents department at headquarters. He'd left the bureau to run his own document-examination service so he could spend more time with his children, Robby and Stephanie.

"How's Margaret?" Sachs called into the speaker.

"That you, Amelia?"

"Yup."

"She's fine. Haven't seen her for a few days. We took the kids to Planet Play on Wednesday and I was just starting to beat her at laser tag when her pager goes off. She had to go kick in somebody's door and arrest them. Panama or Ecuador or someplace like that. She doesn't give me the details. So, what's up?"

"We're running a case and I need some help. Here's the scenario: perp was seen writing his name in a security desk sign-in book. Okay?"

"Got it. And you need the handwriting analyzed?"

"The problem is we don't have any handwriting."

"It disappeared?"

"Yep."

"And you're sure the writer wasn't faking?"

"Positive. There was a guard who saw ink going on paper, no question."

"Anything visible now?"

"Nothing."

Kincaid gave a grim laugh. "That's smart. So there was no record of the perp entering the building. And then somebody else wrote their name over the blank space and ruined whatever impression there might've been of his signature."

"Right."

"Anything on the sheet below the top one?"

Rhyme glanced at Cooper, who shone a bright light at an acute angle on the second sheet in the log – this, rather than covering the page with pencil lead, was the preferred method to raise impression evidence. He shook his head.

"Nothing," Rhyme told the document examiner. Then asked, "So how'd he pull that off?"

"He Ex-Laxed it," Kincaid announced.

"How's that?" Sellitto called.

"Used disappearing ink. We call it Ex-laxing in the business. The old Ex-Lax contained phenolphthalein. Before it was banned by the FDA. You'd dissolve a pill in alcohol and make a blue ink. It had an alkaline pH. Then you'd write something. After a while, exposure to the air would make the blue disappear."

"Sure," said Rhyme, recalling his basic chemistry. "The carbon dioxide in the air turns the ink acidic and that neutralizes the color."