"Even without the cuffs," Kara said softly, "that girl never had a chance of getting away."

"Is that rare? The knot?"

She explained that, no, anyone with a basic knowledge of Houdini's routines would know it. The castor oil in the makeup, Kara continued, meant that he was using very realistic and durable theatrical cosmetics, and the latex was, as Rhyme had suspected, probably from the fake finger cups, which were also popular magician's tools. The alginate, Kara suggested, wouldn't be from dental work but was used to make molds for latex casting, probably for the finger cups or the bald cap he'd worn in his janitor disguise. The disappearing ink was more of a novelty, though some illusionists occasionally used it in their shows.

Only a few things were unique, she explained: the circuit board (which was a "gimmick," she said, a prop the audience can't see), for instance. But he'd made that himself. The Darby handcuffs were rare. Rhyme ordered someone to check out the escapology museum in New Orleans that Kara had mentioned. Sachs suggested they take the responding officers, Franciscovich and Ausonio, up on their offer to help. This was the sort of assignment that'd be perfect for a couple of eager young officers. Rhyme agreed and Sellitto arranged it through the head of the Patrol Services Division.

"How about his escape?" Sellitto said. "What's the deal where he changed into janitor clothes so fast."

"'Protean magic' it's called," Kara said. "Quick change. It's one of the things I've been studying for years. I just use it as part of my routines but there're some people, it's all they do. It can be amazing. I saw Arturo Brachetti a few years ago. He could do three or four dozen changes in one show – some of them in under three seconds."

"Three seconds?"

"Yeah. And see, true quick-change artists don't just change clothes. They're actors too. They walk differently, hold themselves differently, speak differently. He'll prepare everything ahead of time. The clothes are breakaway – they're held together with snaps or Velcro. Most of quick change is really quick strip. And they're made of silk or nylon, real thin, so we can wear layers of them. I sometimes wear five costumes under my top outfit."

"Silk?" Rhyme asked. "We found gray silk fibers," he explained. "The officers on the scene reported that the janitor was wearing a gray uniform. The fibers were abraded – sort of buffed to a matte finish."

Kara nodded. "So they'd look like cotton or linen, not shiny. We also use collapsible hats and suitcases, shoe coverings, telescoping umbrellas, all kinds of props that we hide on our bodies. Wigs, of course."

She continued, "To alter a face the most important thing is the eyebrows. Change those and the face is sixty, seventy percent different. Then add some prostheses – we call them 'appliances': latex strips and pads you put on with spirit gum. Quick-change performers study the basic facial structures of different races and genders. A good protean artist knows the proportions of a woman's face versus a man's and can change genders in seconds. We study psychological reactions to faces and posture – so we can become beautiful or ugly or scary or sympathetic or needy. Whatever."

The magic esoterica was interesting but Rhyme wanted specific suggestions. "Is there anything concrete you can tell us that'll help find him?"

She shook her head. "I can't think of anything that might lead you to a particular store or other place. But I do have some general thoughts."

"Go ahead."

"Well, the fact he used the changing rope and finger cups tells me he's familiar with sleight of hand. That means he'll be good at picking pockets, hiding guns or knives or things like that. Getting people's keys and IDs. He also knows quick change and it's obvious what kind of problem that'll be for you. But more important – the Vanished Man routine, the fuses and squibs, the disappearing ink, the black silk, the flash cotton means he's a classically trained illusionist."

She explained the difference between a sleight-of-hand artist and a true illusionist, whose acts involved people and large objects. "Why's that important for us?"

Kara nodded. "Because illusion is more than just physical technique. Illusionists study audience psychology and create whole routines to trick them – not just their eyes but their minds too. Their point isn't making you laugh because a quarter disappears; it's to make you believe in your heart that everything you see and believe is one way when in fact it's the opposite. There's one thing you'll have to keep in mind. Never forget it."

"What?" Rhyme asked.

"Misdirection… Mr. Balzac says it's the heart and soul of illusion. You've heard the expression that the hand is quicker than the eye? Well, no, it's not. The eye is always quicker. So illusionists trick the eye into not noticing what the hand is doing."

"Like, you mean, diversion, distraction?" Sellitto asked.

"That's part of it. Misdirection is pointing the audience's attention where you want it and away from where you don't want it. There're lots of rules he's been drumming into me – like, the audience doesn't notice the familiar but're drawn to novelty. They don't notice a series of similar things but focus on the one that's different. They ignore objects or people that stand still but they're drawn to movement. You want to make something invisible? Repeat it four or five times and pretty soon the audience is bored and their attention wanders. They can be staring right at your hands and not see what you're doing. That's when you zing 'em."

"Okay, now there're two kinds of misdirection he'll be using: first, physical misdirection. Watch." Kara stepped near Sachs and stared at her own right hand as she lifted it very slowly and pointed to the wall, squinting. Then she dropped her hand. "See, you looked at my arm and where I pointed. Perfectly natural reaction. So you probably didn't notice that my left hand's got Amelia's gun."

Sachs gave a faint jump as she glanced down and saw that, sure enough, Kara's fingers had lifted the Glock partway out of the holster. "Careful there," Sachs said, reholstering the pistol. "Now, look in that corner." Pointing with her right hand again. This time, though, Rhyme and the others in the room naturally looked at Kara's left hand.

"Caught my left hand, didn't you?" She laughed. "But you didn't notice my foot, pushing that white thing behind the table."

"A bedpan," Rhyme said acerbically, irritated that he'd been tricked again but feeling he'd scored a point or two by mentioning the indelicate nature of the object she'd moved.

"Really?" she asked, unfazed. "Well, it's not just a bedpan; it's also a misdirection. Because when you were looking at it just now, I got this with my other hand. Oh, here," she said. "Is this important?" She handed a canister of Mace back to Sachs.

The policewoman frowned, looked down at her utility belt to see if anything else was missing and replaced the cylinder.

"So, that's physical misdirection. That's pretty easy. The second kind of misdirection is psychological. This is harder. Audiences aren't stupid. They know you're going to try to trick them. I mean, that's why they've come to the show in the first place, right? So we try to reduce or eliminate the audience's suspicion. The most important thing in psychological misdirection is to act naturally. You behave and say things that're consistent with what the audience expects. But underneath the surface you're getting away with…" Her voice faded as she realized how close she'd come to using the word that described the death of the young student that morning.

Kara continued, "As soon as you do something in an unnatural way, the audience is on to you. Okay, I say I'm going to read your mind and I do this."

Kara put her hands on Sachs's temples and closed her eyes for a moment.