"If anything happens to Conrad," said Elizabeth, "I will hold you personally responsible."

"I told him not to go on a walk with Flavian," said Christopher.

"Yes, and that's why he went," said Elizabeth. "If only you'd learn to keep your mouth shut . . . ."

Bernard laughed. "Small chance of that," he said. "Anyway, why shouldn't Conrad take a walk with Flavian? The rest of us had to, at one time or another. It's practically a rite of passage."

It was true. I had been on that walk with Flavian, when Bernard and I were both new. We had run into a salamander, and it had ended with me needing sixteen stitches and Bernard unable to sit down for a week. Christopher did warn me—"I shouldn't go if I were you, Hester; hiking is not one of the mandatory subjects"—but I'd trusted my previous experiences with teachers more than I'd trusted Christopher; and besides, my name isn't Hester. It wasn't always Henrietta, either. Most people are born with their names, and some people choose them—like Millie—and some have new names thrust upon them. That's me.

"It's just too bad Conrad is missing the travelling show," I said. "It won't be the same without him." I liked Conrad. He was from another world, and had only been at the castle for three weeks, and could barely do any magic. When he was around, he was the one who was wrong-footed and strange.

"That's what I told him," said Christopher.

But there wouldn't be any lessons until Monday, and we'd managed to leave the castle for once without being saddled with a chaperone, and without anyone being confined to the grounds for some wrongdoing or other. Elizabeth wanted to see the acrobats, and Jason wanted to see the menagerie, and Bernard had heard that they actually battered chocolate bars and fried them. Christopher acted like he didn't care, but he kept forgetting not to smile.

I could hear the show before I saw it, brass and drums and laughter and the murmur of crowds. Half the village was there, and good parts of two or three of the other villages around besides, milling about between the long striped tents. I could smell it, too, and I wrinkled my nose—there was a menagerie around here somewhere. Bernard's nose, more helpfully, led him to a cart where a man was selling all sorts of things, battered and fried. So we all had deep-fried chocolate bars. Christopher somehow ate his neatly, but soon Bernard, Elizabeth, Jason and I were all sticky, smeared with chocolate, and sugar-stupid.

A sign next to the entrance of one of the tents invited passers-by to "MARVEL at MASTER DODD'S collected FREAKS of NATURE." On display, the sign promised, were the Siamese twins, the ugliest man on earth, the tattooed lady, Tom Thumb, and the mermaid.

Elizabeth went all gooey and wanted to see the mermaid. Christopher said it wasn't a mermaid, there weren't any in this series, it was just a woman wearing a stitched-together tail and not much else. Jason said maybe she came from a different series, like Millie and Conrad. Bernard leered and wanted to know what was wrong with a woman wearing not much. Elizabeth frostily said she didn't want to see the mermaid after all.

That made it two to two. They turned to me, and I shrugged and said no. Christopher looked smug and Elizabeth looked righteous; Jason looked like a disappointed puppy and Bernard looked angry and betrayed—the two of us were usually allies of a sort, maybe because we came to the castle at the same time. It was the opposite result to what I would have wanted, but the thought of staring at people in boxes somehow sent prickles all up my neck. I found myself on the wrong side of stares too often—a small, flat-faced, slant-eyed girl in a crowd of bloomingly healthy English children. I mean, I am English. I have papers that say so, with a wax seal and everything. But.

We kept walking, and came to a tent about the size of a bathing hut. Its sign said "Gypsy Fortune-teller MADAME ZENOBIA Sees All and Tells All," followed by a row of mystic symbols. Christopher stopped dead. "Oh," he said. "I think I need to talk to her."

"We can't see a mermaid, but you need to talk to a Gypsy fortune-teller?" Bernard demanded. "If you want some charlatan to foretell doom in your future, you can just wait for your next letter from—"

Elizabeth grabbed his arm. I knew from experience, whenever I was about to make some social misstep, those nails were sharp. "If you finish that sentence," said Elizabeth, "I shall call Gabriel."

"You wouldn't," said Bernard.

"I will," said Elizabeth. "What do you mean by picking a fight with Christopher here; do you have any concept of how flammable ordinary people are—"

Bernard and Elizabeth didn't notice, but the ordinary people at the show were safe from Christopher. He wasn't listening. He had already gone into the fortune-teller's tent. I crept closer to listen, but I couldn't understand the strange, chopped-up language that they were speaking—at least, the fortune-teller was speaking it. Christopher's replies were short and stumbling.

"What are they saying?" Jason hissed in my ear.

I frowned. Jason was no good at sneaky. I didn't answer at first, but I saw that Jason would just repeat his question if I didn't. "Shh," I hissed back. "I don't know."

Just then, I heard something I did understand—the soft rustle of Christopher's clothes as he stood up, and footsteps. I yanked Jason out of the way and pretended I'd been watching a stilt-walker making his way through the crowd.

"What was that about?" said Jason. "Is she really a Gypsy fortune-teller?"

"Of course not. She's an Irish Traveler; it's entirely different," said Christopher. He was walking quickly, towards the edge of the green where the circus' wagons were parked, and the rest of us had to hurry to keep up. "But she really is a sister in the Order of St Ahasuerus, and that means I really do owe her a favor. I travelled with them for a while, you know."

We did know. Or, at least, if this was the first time I'd heard of the Order of St Ahasuerus, we all knew that Christopher had left with the travellers when he'd gone off to find Millie. There was a short, meaning silence. None of us had quite forgiven Christopher for going off to rescue Millie without us.

"What does she want from you?" Elizabeth said finally.

"She has suspicions about this show," said Christopher. "Children have been disappearing, when it passes through a town."

"Kids do run off with the circus," said Jason.

"Yes," said Christopher, "but Madame Zinnia has been with the show for six months, and she says they're not here. There's a thing that the master of the show keeps in his wagon that, as she puts it, stinks, and it's keeping her from sniffing out what's going on. She hasn't been able to lift it, but she thinks that maybe I can."

This was better than mermaids any day, and almost as good as deep-fried chocolate bars. "Which one's Master Dodd's wagon, then?" said Bernard.

"Wait, but look, Christopher," said Elizabeth. "Why do we have to sneak around? If Master Dodd is some kind of monster who eats children, that's Chrestomanci business."

"If it's Chrestomanci business, then it's my legitimate business," said Christopher. "Although, I'd appreciate it if you didn't mention that to Madame Zephyr. Her goals are basically the same as Gabriel's, but historically the Order hasn't got on well with him, or his predecessors."

Christopher stopped, and so did the rest of us, short of the edge of the crowd. We weren't near enough to the wagons and horses to draw looks from the knot of large men who sat there. "I'm going to need a distraction," he added.

Jason grinned. "Right," he said. "I'll just—"

"Not a magical distraction," said Christopher. "I don't know what we're dealing with here; I'd rather that went both ways."

"The big red wagon," I said. "That's the one you want them to be looking away from, yes?"

"Yes," said Christopher, "but—"

"Right, then," I said. Let the rest of them get started, and they'd talk all day. I walked towards the wagons.

One of the men set down his mug on a barrel, and stood. He had a wide red face and a wide red waistcoat, and he loomed over me like a mountain. "Hey, there, missy," he said. "You can't—"

I kicked him in the right shin, and then in the left one, and turned and sprinted away as he bellowed. I nearly ran into Elizabeth and Bernard. Stupid! Elizabeth had probably followed me to try and stop me from doing what I'd just done. I didn't know why Bernard was there. One look at the red mountain bearing down on us and they ran too.

"Have you gone mad?" panted Elizabeth. "That man's four times your size! He could have flattened you!"

"But he didn't," I said. "Most people aren't prepared to be kicked. Especially not by a little Chinese girl." The posh clothes I'd been wearing since I came to the castle didn't hurt, either.

"You're not Chinese," said Bernard, as we ducked between two wagons, heavy footsteps falling close behind us. Trust Bernard to fix on an unimportant detail! But it's not really unimportant to me.

"I know that," I said. "But I don't think he does."

Elizabeth looked over her shoulder. "Anyway, I don't think it's worked," she said. "The rest of them aren't chasing us. They're looking out more sharply than ever."

"Watch," I said. And I must have been spending too much time around Christopher, because I added, "And learn."

We came to a crowd of horses placidly eating their lunch. I skidded to a stop, took a breath, and screamed. I may be small, but when I scream I put my lungs into it. Half of the horses got white around the eyes, and tried to bolt. The rest of them did bolt, pulling up stakes, trampling things in all directions. The water trough was overturned, and the man who'd been chasing us slipped and fell into the mud—not that he was my main worry right now. Bernard had a hand around my arm and he dragged me out of the way of a couple of horses bearing down on us. I didn't see Elizabeth.

And that was the trick that earned me the name Shrieking Hetty on the streets of Liverpool.

I didn't think any of the circus people would have much attention to spare for Christopher now. If he was half as good as my brother David, he would get his stinky thing without a problem—and I don't mean to insult my family's honor but Christopher is twice as good as my brother David. He wasn't going to help me escape from the angry men chasing me, though. That I would have to do myself.

I dashed back into the crowd, Bernard panting behind me. He was too big to duck between the bewildered and shouting villagers the way I did, and he clearly didn't have the wind for this sort of thing. I hadn't asked him to follow me—a man, thinner than our first pursuer but taller, with wicked-looking gnarled hands, made a grab for Bernard as we passed by the battered-and-fried cart. I snatched up the pot of oil, threw it in the man's general direction, got Bernard's hand, and ran for the freak show.

It was a shove and a half to get through the narrow tent, but the men chasing us seemed to be slowing down. I didn't, and I didn't let Bernard. We dashed past the Siamese twins—not Siamese, or even conjoined; I'd bet they weren't even twins—and Tomb Thumb—actually quite small—and out the other side. The parade was passing, and I slipped between two startled elephants and hoped Bernard was behind me. He was, and the large angry men weren't. We more-or-less fell into a patch of shade next to the big tent and sat catching our breath.

"It was just a lady in a stitched-together tail after all," said Bernard. "Not a mermaid."

"Yes," I said. You get used to wrenching conversational turns when you're around Bernard. "Did you enjoy the view?"

I didn't think Bernard could get redder than he'd got from running, but a moment before he'd been rhubarb and now he was a tomato. "Yes," he said hoarsely. "Er, of you. That was amazing."

I don't know what sort of produce I looked like, but I felt very hot. Just meaningless gallantry—except that Bernard is no more gallant than I'm a kangaroo. The idea that clever, obnoxious, posh Bernard was nursing a hopeless admiration of me was stupid, but it did explain some things. Like why he'd rushed after me when I'd gone to make a diversion. And why he was looking at me like saying that was the scariest thing he'd ever done.

I remembered the way his hand had felt on my arm when he'd dragged me out of the way of the horses, and I leaned in towards him. Sometimes I don't know what I'm going to do until I do it. I still can't be sure what I was about to do just then, because that's when Elizabeth's voice behind us said, "Ahem."

I couldn't see her, but I should have known.

"Christopher's got the thingummy," she said. "He says it's safe to use magic now. Come on." So Bernard and I went invisible too and followed her back to Madame Zenobia's tent.

It was your standard bigger-on-the-inside-than-the-outside job, full of gauzy curtains and tasseled cushions and Oriental carpets, and smelling of incense. Jason was poking at some odds and ends—a crystal ball, a mummified monkey's paw, a deck of Tarot cards—in a happy Jason way, and Christopher was lounging on some of the cushions in an indolent Christopher way. Sitting in a great wicker chair like a throne was an old lady—not as old as Gabriel, but who is—in bright layers of flouncy skirts and shawls, with a scarf wrapped around her steel-grey hair and big hoops in her ears. If she wasn't a Gypsy, she was doing a good imitation of one.

"There you are," said Jason, as we blinked back into visibility. "Madame Zenobia's been saying—"

"Meg, love," said the not-a-Gypsy. "Madame Zenobia is for the customers."

"Why?" I said.

She laughed. "You wouldn't want your palm read by Meg Reilly, would you?"

"I wouldn't want my palm read at all," said Bernard. "Now, give me a microscope and a spoonful of good Assam and I could tell you how the markets will open on Monday."

"Be that as it may," said Christopher, because nobody wants to let Bernard get started on finance, "we've been trying to work out what this artifact is. It seems to have some connection to—"

There, on a velvet tablecloth on a rickety folding table, was something I never thought I'd see in England, outside my mother's kitchen. Two sticks, arranged in a cross, and woven through with silk thread; a shifting square of blue and green, red, white and yellow that fascinated the eye. "It's an endless knot," I said.

"Don't look at it," said Meg sharply.

I wrenched my eyes away. I didn't understand, but I'd run with my brother's gang and I'm an enchantress; I know how to listen first and ask questions second. What you don't understand can cut you just as sharp.

"Why not?" I said. "They're good luck."

"Good luck for who?" said Meg. "Good luck for Master Dodd would be bad luck for you, I'm thinking."

That name, on top of the knot like that, jostled something loose from my memory. I still didn't understand, but I was beginning to see the shape of it. "Not Dodd," I said. "Bdud. Demon."

"An endless knot," said Christopher. "What does it do?"

"It's a spirit cage," I said. "It traps demons and evil spirits and things so they can't make trouble in your house. Sometimes people make them as houses for gods, but that's a different sort . . ."

"And children?" said Meg.

I had to try really hard not to look back at the endless knot on the table. "You could make one to trap children," I said.

"Bdud," spat Meg. "Shouldn't be here, in England."

"And I suppose if he were back in Tibet he'd be welcome to ensnare children as much as he liked?" said Elizabeth.

Meg shrugged. "The Order's concerned with balance," she said. "In Tibet, there'd be people who knew what he was, and how to oppose him. Here, there aren't." She turned an unsettling steely gaze on me. "Or are there?"

Not fair, to ask that. "I was six when we left Tibet," I said. "And this . . . this is priest's work."

"Huh," said Meg, and turned back to Christopher. No slaps like David, or gentle encouragement like Flavian, or sarcasm like Gabriel. So either you were good enough, or you weren't worth her time? It nettled.

"To exorcise a demon," I said, "you need an endless knot to trap it—we've got that—and a phur ba, I guess you'd call it a ritual dagger, to fix it in place. I haven't got one of those." My grandfather's phur ba, made of meteoric iron and carved with three faces of Dorje Phurba, was long gone. Probably fallen into the hands of the lamas and melted down for scrap.

"Haven't you?" said Meg. "Look around yourself. What do you see, that you can't see past?"

Bernard did a cryptic crossword every Sunday. Christopher and Elizabeth and, lately, Conrad, would help him with it, calling out suggestions, puzzling over clues. Not me. "I hate riddles," I said.

"The whole theory doesn't make sense," said Bernard. "If this thing is a trap, it should have been put somewhere where someone could fall into it. What it was doing was stopping Meg from spying on Master Dodd. Protects the house from intruders, right?"

"Master's knot, master knot," said Christopher. "Those connections we found . . ."

"They might lead to other knots," said Jason, "which are where kids can find them."

"Or were," said Elizabeth grimly. She closed her eyes and put her hands over the endless knot, and started teasing strings loose. The shape of the physical object didn't change. These were strings of magic: blue, green, red, white, yellow. "There's five. Isn't that lucky."

"We'll find them," Christopher said. "Give us each a string."

Christopher took blue, for space, and Bernard took red, for fire. Jason took yellow, for earth, and Elizabeth kept white, for water. I took green, for air, and followed my string invisibly back out into the crowds.

I found the other end of it in the pocket of a small boy—well, not smaller than Jason, actually—chattering to his father about the elephants. I conjured it into my hand, and then—I can't explain what I did next.

I mean, I'm an enchantress, and I'm not feeble-minded. I knew I wasn't supposed to be looking at the knot. But I had never seen anything like those colors.

Then the parade was sweeping by, towards the big tent. The crowd followed, moved along by the insistent drumbeat, humming with excitement, and I moved with them. The show was starting at last! I clutched my treasure, the bright tangle of string, and found a ringside place in the big tent. Something exciting was about to happen.

A small round man in a tall hat stood in the middle of the ring. He raised his hands and the crowd's hum fell to a murmur. "Ladies and gentlemen, and children of all ages!" he—I don't know why I thought of the word keened. "Take your seats beneath the big top, and welcome to Master Dodd's Show of Marvels! I am Master Dodd, at your service, and this is what I offer you: the finest riders, aerialists and acrobats in Europe, the most wonderful beasts, the most daring acts of skill and illusion, the greatest spectacle on Earth! Lend me all your senses, and let the spectacle begin!"

The drums got louder and faster, bells clattered, and from the opposite side of the tent the performers started coming in. Stilt-walkers bobbed, and tumblers turned handsprings; stunt riders leapt from horse to horse, elephants lumbered and bears shambled. Overhead, men in bright leotards swung from trapezes and tossed glittering women back and forth between them. Another aerialist did a frantic, spinning dance on the high wire.

"And now," said Master Dodd, "I'll need five volunteers from the audience. Step up, ladies and gentlemen."

I was on my feet before I knew it, ducking under the barrier to stand in the ring. I was joined by a tall boy with elegant clothes, and a pretty blonde girl, nearly as elegant. Two more boys made their way out of the crowd, one small skinny one with a cheerful grin and one wide, blunt-featured one with disorderly tufts of medium-brown hair and eyebrows. The tall boy looked around himself with a vaguely puzzled frown, and took one of the blonde girl's hands in one of his, and one of the blunt-featured boy's hands in the other. The blunt-featured boy reached for my hand, and I was about to show him what I do to people who touch me without permission, when his fingers grazed mine and I came back to myself with a lurch. Bernard's eyes met mine and I knew he was feeling about the same way.

"You were all completely bewitched," breathed Christopher, too low for anyone but us to hear. "He shouldn't be able to do that."

The spectacle was even more spectacular in its true form. There were no stilt-walkers, but long-legged giants with backwards feet. The aerialists flew on drums, not trapezes, and I do mean flew. Glittering birds with women's faces fluttered among them. The bears had claws two feet long, and eyes like the edges of a fire. The elephants' feet shook the ground when they hit, and on their backs dancers with snake's tails entwined and slashed each other with knives. In the middle of it all stood Master Dodd, a small round man in a tall hat, with blue skin and twenty arms and a mouthful of fangs, surrounded by a halo of flames.

"God," whispered Jason, "they're all demons."

They weren't, actually—almost half of the performers were human, and going through their acts like dreamers. I felt a fury take hold in me. Creatures of illusion, how dare you toy with my mind.

"Do you know what to do, Henrietta?" Christopher whispered.

I didn't. My anger had warmed, but not enlightened me. Look around yourself, Meg Reilly had said. What do you see that you can't see past? I looked past my friends, past the demons, past the mesmerized crowds. But I couldn't look past the walls and roof of the tent. And what's a phur ba but a tent stake?

"There's something I need to get," I hissed. "Can you make an illusion of me for a minute?"

Christopher nodded, and I turned Bernard's hand loose and pushed invisibly through the crowds once more, towards an anchor point of the tent. When I wriggled outside, I admit, it occurred to me that I could keep running. Then I closed my hand around the tent peg, and it was a sort of possession, but not the sort that had muddled my brain when I'd looked at the endless knot. This was—do you know the expression, self-possessed? It's more literal than you might think.

When I was back in the ring and facing Master Dodd, I raised my phur ba. Christopher, on the other side, raised the master's endless knot—nobody ever accused Christopher of being slow on the uptake. And I remembered what to say, which I don't think I ever learned in this life.

"Open the golden lock of the north," I said. "Open the silver lock of the east. Open the iron lock of the south. Open the copper lock of the west. The doors must be opened. Open the golden door, the silver door, the iron door, the copper door. Open the doors, we are coming to make the offering."

Then I drove my phur ba into the earth, and the flying demons, the snake demons, the bear and elephant demons all vanished. So did Master Dodd, and so did Christopher.