Millie found that she really wasn't equal to Sunday lunch so soon after two substantial breakfasts, but she sat with Henrietta and Christopher and chatted as they ate. She watched with interest as Henrietta silently crammed a vast amount of food into her spindly frame and Christopher complained about the indignity of being hustled off the church behind Gabriel's flapping coat tails like a small child.

"Anyway, I've worked out a way to avoid actually dying of boredom at church. Though it would jolly well serve them right if I did die of it one day," said Christopher, shooting a black look in the direction of Gabriel at the other side of the table and spearing his broccoli savagely. "It's a bit like your usefully stupid expression, Millie. I conjure a sort of apparition screen of me wearing it, and then I can skulk behind it out of sight of anyone. I just sit there and read a book Mordecai gave me about spin bowling - look, it just fits into my breast pocket, so nobody notices me take it into church."

"That does sound useful," Millie agreed, absent-mindedly eating some of Christopher's Yorkshire pudding. "Do you do the apparition thing on both sides of you?"

"Well, I sat next to a pillar, so I didn't have to. But I'll do it on all sides next time. Of course, it wouldn't be any good if Gabriel were next to me, he'd spot what I was up to a mile off. I was surprised that Flavian didn't tumble to it, to be honest, but he doesn't seem himself today."

"Flavian's our tutor," Millie explained to Henrietta, although the girl was showing no particular interest in the conversation. "He's that one over there - and you're right, Christopher. What a peculiar green colour his skin has gone."

"Anyway," said Christopher, sighing, "it was all going well until the time came for the vicar to say that thing about the sign of peace and everyone to shake hands. I was completely absorbed in reading about the technique and I was sort of practicing with my arm ever so slightly, how you'd put the spin on the ball just before letting go, you know. But I was doing it just as Rosalie leaned over to shake my hand. All she could see was the apparition, of course, so she didn't know I was sort of bowling, and she came too close, and I - I ended up hitting her in the chest." Christopher blushed crimson as Millie guffawed with delighted laughter.

"Not hard, I hope?," Millie managed to ask between spurts of laughter.

"I don't think it hurt her. But she wasn't pleased," Christopher said. Christopher did not enjoy being made to look foolish and he'd felt pretty mortified at the time, but Millie's merriment made him see the matter in a different light and now his lips twitched upwards. Before long he too was laughing and even Henrietta was seen to give a very slight smile before she applied herself again to her roast beef.

The mood of gaiety lasted them through till the pudding plates were being cleared away, at which point Dr Simonson stalked past the table where the children were sitting and laughing. "Millie, bring your new friend up to Gabriel's study after lunch. You come too, Christopher. You might learn something," he said without stopping.

"You'd think I'd deserve a day off from learning things," Christopher grumbled as they pushed back their chairs, although he was secretly quite keen to see how Gabriel proposed to assess the latent magic of someone seemingly unable to perform a simple spell. Millie ignored him and said to Henrietta, who was somewhat pale beneath her many freckles, "Don't be alarmed by Dr Simonson. He just looks sinister because of his odd pointy beard. He's really quite nice." She would have liked to squeeze Henrietta's hand, but didn't quite dare.

In Gabriel's study, the darkness of the drear wintry weather seemed to have seeped into the dark wood panelling and the lamps glowing on Gabriel's vast desk seemed only to bring out shadows. Millie wondered why it felt so different from the companionable, almost cosy, afternoons she had spent in it with Gabriel the previous week. She risked brushing her hand against Henrietta's as they stood in front of Gabriel's desk, surveyed gravely by him and Dr Simonson, and felt Henrietta freeze instinctively in surprise but then look at Millie with the hint of a grateful smile.

"I feel sure that you will appreciate the extent my difficulty, children," Gabriel said, looking as though he doubted it very much. "Here we have a young person who is clearly imbued with a great deal of magical ability but who is unable to access it so as to allow us to observe its nature and extent. When we came upon Christopher here, we were able to observe that he had more than one life and should have had nine, making it clear that he was a nine-lived enchanter, who invariably wield unparalleled power, for good or ill. When you arrived at the castle, Millie, you did so having extracted a life from a nine-lived enchanter without his knowing it and used it to cross between worlds, which only a user of extremely potent magic could begin to dream of doing."

"Sorry again for that," Millie muttered to Christopher. He flashed her one of his most handsome and gallant smiles in return, his black eyes gleaming. "Don't mention it, Millie," he said in his most lordly voice. "Any time." Wondering vaguely why she was blushing, she grinned back at him.

Gabriel raised his voice slightly as he started to speak again. "The other children who are educated here along with Christopher - Jason, Elizabeth, Bernard, and the twins - underwent very rigorous tests to ensure that their magic was sufficiently strong to allow them to benefit from the instruction available here. They each performed several demonstrations of their magical abilities before being offered a place; many others were turned away."

Millie gulped. She hadn't known this and felt ever more dreadful about having invited Henrietta to the castle only to undergo a series of humiliating tests. "Perhaps Henrietta would prefer it if Christopher and I weren't here," she suggested, awkwardly looking at Henrietta.

Henrietta shrugged with a characteristically brusque movement, so different from the fluid motions when she was on the trapeze. "I don't care," she said, and Millie nodded. She was beginning to see that Henrietta's apparent lack of pride was in a strange way not dissimilar from Christopher's excess of it.

There followed a long process of Gabriel asking Henrietta to perform spells and enchantments, and Henrietta trying with a grim expression and without success to comply whilst Dr Simonson walked around and around her, squinting alarmingly. After a while, Millie and Christopher tired of standing and despaired of being asked to sit down, so they sat together on a small but sturdy mahogany table in the corner.

"Why does he keep asking her?" Millie whispered to Christopher in anguish when Henrietta failed to produce so much as a whisper of motion after several minutes attempting to raise a wind. "Anyone can see she can't do it."

"Do you think Dr Simonson's sort of measuring something whilst she tries? He's certainly staring and nodding a lot," Christopher whispered back, wriggling in discomfort.

"Next, please attempt to render this desk invisible," Gabriel carried on remorselessly. "Try first using whatever approaches or methods suggest themselves to you. If that fails, we shall see whether you can work a spell which I shall teach you."

Henrietta stared dumbly at the table for a minute or so, and then looked at Gabriel with mute hostility.

"Very well," Gabriel intoned. "Now, repeat the following words whilst you hover your hands over the table: -"

"I. CAN'T. DO. IT." Henrietta suddenly spoke for the first time in twenty minutes and she slammed her hands down on the table with unprecedented ferocity.

The room shook very violently. Books and artefacts began to slide off the shelves. The ancient stone walls started to creek and subside. A hole opened up in the floor of the study through which the table slowly slid as though it were being sucked down by a plug to the floor below. Henrietta stood immobile watching the heaving destruction and had Mille not leapt up and pulled her unceremoniously back from the hole it seemed likely that she would have allowed herself to be absorbed into it along with the table.

Gabriel stepped nimbly back from the hole as it continued to expand. Before long, he and Dr Simonson had retreated to one corner of the room whilst the three children huddled in the opposite corner, the floor at the four corners of the room being effectively all that was left of it. The hole had reached within an inch of where Millie was standing, pressed back against Christopher who in turn was pressed against the wall with Henrietta beside them, when in alarm Christopher raised his hand and then decisively let it fall on a sideways tilt. "That's enough," he said firmly as he did so, and the hole stopped growing. The castle walls stopped creaking and there was a heavy silence in what was left of the room.

"Well, it looks as though you can do magic, after all," Millie said cheerfully to Henrietta, as they peered down the hole to the floor below. Rosalie and Mordecai were standing next to a pile of broken furniture looking up at them. They seemed put out.

"Oh dear. I'd forgotten that Rosalie's sitting room was beneath my study," Gabriel muttered looking suddenly guilty and more than usually human. "No wonder she looks unhappy. My apologies, Rosalie!" he called loudly. "We'll have things readjusted shortly. We were just testing the abilities of our new friend here."

"On this evidence, her abilities seem more powerful than they are considerate," replied Rosalie, crossly. "Do put things back as quickly as you can, Gabriel, there's more than enough to do when planning a wedding as it is, let alone with tables and chairs falling on us with no provocation whatsoever."

"You'd think nobody had ever got married before, the way that she carries on," Christopher muttered, whilst Gabriel started moving his hands very subtly and the errant items of furniture started floating back up to their proper place, repairing themselves as they went. Millie just caught a cheerful wink from Mordecai in the children's direction before the floor reassembled itself and Gabriel stepped briskly onto it.

"Not a bad effort, Christopher," he said, "but it would have been more efficient to perform the stopping spell and the reversing spell simultaneously."

"I like that!" Christopher burst out indignantly. "At least I did stop it, rather than waiting for the whole castle to fall apart which I can only assume is what everyone else was doing."

"Dr Simonson and I were waiting to see whether and how Henrietta here would think to stop it," Gabriel replied drily as he sat back down in his chair. "You and Millie were perfectly capable of taking appropriate action, as indeed you demonstrated, if you felt yourselves to be in immediate danger."

Henrietta was still staring, as if unable to believe that she herself had had anything to do with what had just happened.

"I didn't do it on purpose," she said, when she at least realised that everyone was looking at her. "I didn't know how to stop it."

"Hmmmm," said Gabriel. "I wonder. Millie, you said that you thought Henrietta used magic in her - ah - her acrobatic endeavours at the circus?"

"Yes, I'm sure of it. You were plummeting to the ground, you know, headed straight down like a diver, and then you swooped up on a curve as though caught by the wind, all the way back up to grab on to the trapeze. Magic seemed the only explanation- and anyway, I could feel it."

"I agree," put in Christopher. "It was obvious that - ow!" He turned to glare at Millie and then, meeting her eyes, bit his lip. "I mean, from what Millie's told me, it certainly sounds as though you must have been using magic," he amended, weakly, and Gabriel fixed a particularly cold stare upon him.

"Are you conscious of using magic when you do these aeronautical exploits, Henrietta?" Gabriel asked, and Christopher breathed an audible sigh of relief that the matter of his odd interjection was not being pursued further.

Henrietta shook her head, and then said, suddenly, "The first time I did the hardest leap, from the highest and furthest trapeze to the other, I remember free falling - I'd misjudged it and wasn't fast enough, I knew I'd never reach it. It's like Millie said - I was hurtling towards the ground and it was getting closer and closer." She closed her eyes with the effort of remembering precisely what she had done and when. "And suddenly I stopped feeling frightened and I felt so angry that I was going to die so young, and then next thing I knew I was soaring back up into the sky. Everyone shouted and screamed that it was a miracle. And then after that I could do the same thing every time without trying, it was just how I took the leaps."

"And have you ever experienced anything similar, apart from on your trapeze? Any incidences of a power to do things which other people can't?"

"Never," said Henrietta, disconsolately, as if knowing it was the wrong answer.

"I don't know," said Millie, suddenly. "You know, when you don't most particularly want to talk to people you seem to be able to disappear extraordinarily quickly. I know you said you're a fast runner, but I wonder whether...". She trailed off, doubtfully. She had only seen Henrietta disappear like that in the dark, and in a confusing labyrinthine circus camp, after all, so it was hard to be sure. In addition, now that everyone was looking at her Millie realised that she was still standing extremely close to Christopher, despite the room having been restored to its usual spacious and hole-free state. She took a hurried step away from him and, more to divert attention from her own unaccountable blushing than from conviction in what she was saying, she carried on.

"Well, what if you can only do magic when you're cross, or frightened, or something - so much so that whatever's normally stopping you doesn't apply? Could it be that you somehow normally impose a restraint on yourself, like silver does to Christopher, but sort of override it when in some kind of extremis?"

Millie had a feeling that this wasn't quite the right way to use the expression "in extremis", which she had only seen before in books and pronounced in a way which made Dr Simonson smile under his beard, but she hoped putting in something in Latin might make her suggestion more compelling. It didn't seem necessary, though. Dr Simonson and Gabriel glanced at once another thoughtfully and Gabriel said slowly, "What an interesting idea, Millie."

"And what an interesting puzzle it would be to unlock that talent," continued Dr Simonson, eagerly, looking like Christopher did when contemplating a new set of particularly fine clothes.

There followed anxious few minutes during which Gabriel and Dr Simonson exchanged phrases like "self-negated magic... not many known cases but always associated with great talent... high degree of transferred aptitudes", during which Henrietta looked anxiously at Millie and Millie could only shrug helplessly. But when Gabriel at last said "...extremely dangerous if not properly controlled, of course" Millie and Christopher both started to grin. And sure enough a minute later, Gabriel turned his steely eyes upon Henrietta and said (in tones which he believed to be avuncular, though none of the children would have guessed it): "Well, young lady. Would you like to stay here and be taught how to properly and responsibly exercise your magical abilities?"