Oz swung the Mini into the bay and stamped on the brakes. The front bumper rocked barely an inch from the brick wall.

"Have you been promoted, Oz?" asked Ess.

"What?"

Ess nodded at the plaque in front of them, which sternly announced that the bay was for the exclusive use of the college chancellor.

Oz dismissed it with a wave of his hand. "You think the old fool will be around at this time of day? He'll have packed his bags and swanned off to his club ages ago. Besides, the man is terrified of me. I can't think why. It's not like I ever actually cursed him. Okay, I've threatened to a few times, but the man is supposed to be a physicist. He's not meant to believe in that sort of thing. Besides, this is close to the hall. Right, everyone out, and bring the baggage, young man."

They decamped from the car, Paul carrying a large cardboard box. Oz opened the boot, pulled out a holdall and draped the shoulder strap over Paul's head. Finally he took a book from the car and slammed the boot shut. Turning, he regarded Paul for a moment.

"No, fine, don't you worry about an old man like me. I'm sure I can manage to carry this book by myself, even though it's heavy." He slapped Paul on the shoulder and laughed as Paul staggered to keep his feet. "This way, men. For England and Lord Harry!"

Oz strode across the small courtyard towards the college entrance, sucking the others along in his wake. He took the steps two at a time and held the door open. Inside he rapped on a door marked 'Porter.'

The top half of the door swung inwards, revealing the angry face of a thin man with a fat moustache and a peaked cap.

"Who the bloody hell is ... oh, Professor, it's you. How are you, this evening? Heard you was sick."

The frown disappeared in an instant, replaced by concerned interest.

"Watchya, Alf. I am as fit as an Olympian god now, thank you very much. How are you? Ruby all right?"

"Champion, thanks. We went for a walk in the park last weekend. Only a little one, mind you, but it's a start. I reckon she'll be able to go to the shops on her own, soon."

"Well, don't rush it. Agoraphobia takes time to conquer."

"Don't I bloody know it. She'd still be trapped indoors, if I had to wait for the bleeding NHS. Grateful to you. Here, the kettle's on. Have a cuppa."

"Maybe later," said Oz. "Just at the moment I'm a bit busy. Is the Carlisle theatre free?"

"Well, nobody's booked it out, not official. Might be a couple of students in it though." Alf said it in a way that suggested students were of no more importance than if the room were occupied by a couple of spiders.

"Excellent. My colleagues and I are going to be working in there this evening. We'd like to be alone."

"No problem, Professor, you know that. Here," he reached out of sight and produced a key, "lock yourself in." He looked suspiciously at Paul and Ess. "There ain't going to be no mess, is there? Blood's a bugger to get out of parquet flooring."

Oz took the key and beamed. "I am happy to inform you we will not be sacrificing any virgins or goats this evening, Alf. The worst might be some chalk marks on the floor, but I promise you that this young man here will ensure the hall is left in pristine condition. If you've gone by the time we leave, give Ruby my felicitations, and I'll drop the key in your pigeonhole."

"Right you are, Professor." Alf touched the peak of his cap and closed the door.

"Have you noticed," said Oz, as he bestrode the corridor, "that the less nominal power someone has in an organisation, the more actual power he wields? Alf could paralyse this noble establishment in thirty minutes. The chancellor, on the other hand, could go missing for a month and no-one would notice. Receptionists, security guards and porters: they're the ones that rule the world. Cross them at your peril. Alf has the power to make a lecturer's life a joy or pure misery, and it's a power he has no compunction in exercising. I've worked hard at ensuring he thinks the sun shines out of my arse, and in return he greases my drawers in the sideboard that is this establishment."

"He greases your drawers?" asked Ess, barely containing her laughter.

"Okay, on reflection that sounded better in my head, but you get my drift. Ah, here we are."

Oz pushed open a set of double doors.

"Out, damn spots!" he roared, pointing to the corridor in a theatrical sweep of his arm. A small group of students looked startled, perched on and around the tiers of seats. They grabbed books and sheaves of notes and scurried towards the exit. Oz stopped a frightened-looking Chinese girl and turned the cover of the book.

"Ah, As You Like It. Well, my apologies for interrupting your read-through, my children, but all the world's a stage. I'm sure you can find an equally quiet spot. I believe MacMillan's free. Exeunt stage right." He smiled as he stepped aside to allow her anxious exit. "Break a leg," he called as they left.

"Really, Oz. You needn't put the fear of God into those poor kids," said Ess.

"They are not poor kids, they are university students. English Lit. students at that. I am a professor. It is one of the few perks of my job to put the fear of Oz in them. Besides, my own students love me. It all balances out in the end. Yin and yang, and all that.

"Now, unpack the bags, dear boy, while I retire to my office for a moment."

Oz left, humming 'If I Ruled The World' to himself.

"He's ..." Paul wasn't sure how to end the sentence politely.

"Larger than life? Absolutely. He's a force of nature. I think if he were shipwrecked on some Pacific island, the natives would worship him as the incarnation of their volcano god. Most of it is pure theatre, of course. When he forgets to play the great Oz, he's really rather sweet, though he'd never admit it. I can understand why girls fall for him. Oh, not me, dear Mother, no. He's not my type at all. Come on, I'll give you a hand with the gear. That's not for eating, you little scamp."

Ess held out her hand, and Scarth reluctantly gave her the candle he had fished out of the carton.

"Ice-cream?" he asked, without much hope.

"I'll tell you what, how about a mint?" she said, fishing in her bag. "There you go, suck on that."

Scarth sniffed the mint suspiciously, took it out of her hand and placed it carefully in his mouth.

"Suck it," said Ess, miming the action. "Oh, okay, crunching it up is just as good, I expect. Whatever."

Paul and Ess knelt by the box and started to arrange its contents on the floor. Paul thrilled to the occasional touch as their hands brushed each other's, pulling out the paraphernalia. He suspected it wasn't entirely by accident on Ess's part, but he didn't complain.

"What's all this stuff?" he asked.

Ess shrugged. "Different people perform magic in different ways. It's like dressing. Do you put your top on before your socks, or after? It doesn't matter, so long as your knickers don't end up on top of your trousers. The basic rituals are the same, but some of the peripherals are optional. Oz does it his way, I do it mine. I, for instance, would not use these."

She held up a three-pack of condoms, holding the corner between finger and thumbnail. She suddenly looked at Paul horrified. "I mean, I wouldn't use them in a ritual, not, erm, I mean, oh, bloody Oz and his infantile humour."

"Ah, you found them," said Oz, from the doorway. "I was going to slip them to you quietly, so as not to embarrass you in front of your boyfriend. No, no, don't thank me, I get a bulk discount."

"You honestly didn't walk down the corridor like that, did you?" asked Ess, flinging the packet back into the box.

"What, you mean this old thing?" said Oz, holding out his arms and treating the pair to a slow spin. He wore a huge white robe that might have once been a marquee. The wide sleeves, hem and neck were embroidered in purple and gold, and cabalistic symbols covered the front and back. A thick guy rope served as a belt. On his head sat a square hat in matching design, with a gold tassel hanging rakishly to one side. He carried a staff fashioned from a long branch of white wood in his right hand.

"These, my cohorts, are the robes of office for a grand wizard of Roke. It is symbolic of my power and authority, and lends me gravitas and dignity." He winked at Ess. "Want to know what I'm wearing underneath?"

"A world of no, Oz. I don't even want to think about it."

"In that case, izzy wizzy, let's get busy. We've only got half an hour."

Paul glanced at his watch. "Half an hour? But I though you said we were doing this at midnight."

"I said the witching hour. You watch Bride of Dracula and think you know it all. The witching hour was never midnight. Seven, that's when the power is at its strongest, and the barriers between the planes are at their weakest. Or eighteen minutes past five, if you prefer. The point is, it doesn't matter. What matters is what you believe, and I believe that we are going to do this at seven, so get your arse in gear and help me set this up."

Twenty minutes later Oz stepped back and admired his handiwork.

"Not bad, not bad," he said. In the centre of the lecture hall he had drawn a circle six feet in diameter, enclosed in a pentagram. At each point burnt a candle. Odd symbols were chalked round about. He fished out an apple and a small bottle of whiskey and placed it carefully inside the circle, stepped back and regarded them critically.

"Just manners," he explained. "Demons expect a libation. It's like offering a cup of tea to the Jehovah Witnesses when they come round. Did you know they've blacklisted my place? Can't think why. It's only a cheap brand, of course. I'm not going to waste a single malt on him. Hmm. I wonder if it's too cheap? Better test it."

He stepped back into the circle, picked up the bottle and took a long swig from it. He shuddered and pulled a face, then replaced the bottle. "Not exactly a Bushmills, but it'll do, I guess."

He turned back to the others, clapping his hands together and rubbing them enthusiastically. "Now then, my occult duo, we need to understand the basic rules, okay? The first rule, absolute and inviolate, is that, whatever happens, you are under no circumstances to enter this circle, understand?"

He looked down at his feet, squarely in the middle of the circle. "Oops." He strode over to Ess and Paul. "No, seriously, I mean it. If you enter the circle while the demon is there, you are in deep doo-doo. Second, under no circumstances allow the circle to be broken. If you smudge out the circle, even a little, we will lose any control over our guest, and he will be free to wreak havoc. Thirdly, do not forget he is a demon, whatever form he presents himself in. Which means he is a lying homicidal maniac. Treat him with caution. Finally, do what I tell you without hesitation. If things go pear-shaped, listening to me may be the only thing that saves your life, understand? We are not playing parlour games here, children, we are risking life and soul. Now, Ess, I need you to take your clothes off."

"What?" said Ess.

Oz shrugged. "Oh, well, it was worth a try. But I'm disappointed you hesitated. We need to make sure Scarth doesn't enter the circle as well. Where is he?"

Paul and Ess look round.

"Scarth?" called Ess.

"He was around here a moment ago," said Paul, looking around frantically.

"You've lost the little bugger?" asked Oz, disbelievingly.

There was a loud and protracted fart from within the seats. Paul bounded up the aisle.

"Found him," he said.

Scarth was sitting hunched on the floor behind a row of seats. His ears drooped, his shoulders sagged and he shook as though caught in a snowstorm.

"Scarth, get out here," said Paul.

Scarth turned eyes as big as dinner plates towards Paul. His cheeks were wet with tears.

"Scarth good," he wailed.

"Yeah, yeah. Good boy. Now get your arse out here."

"Scarth good. Scarth not eat. Scarth sit on hands."

"Fine, just get out here, you moron."

Ess came up beside Paul. "Oh, poor thing. Look at him. He's terrified, poor lamb. Come here, my sweet. What's the matter?"

"Scarth good," wailed Scarth, on the point of sobbing. "Scarth good. Stay with master."

"He's seen the circle," said Paul. "He thinks I'm getting Lord Roath back."

At the mention of the name Scarth covered his head with his hands and wailed.

Ess walked down the row and knelt by the frightened creature.

"It's okay, Scarth. Everything is fine. I'm not going to let anything bad happen to you, understand?"

"Don't make Scarth go in circle. Scarth good."

"Yes, you're a very good little demon," soothed Ess. "We won't make you go in the circle. I promise. Here, take my hand. That's it. Now, I'm going to hold your hand, and I promise you, you're not going in the circle, okay?"

"Not circle?"

"No. Have I ever lied to you, Scarth? I've always given you ice-cream when I promised, haven't I?"

"Ice-cream?"

"Yes. I tell you what. After this is over, I'll get you an ice-cream, okay, even if we have to go to the West End to get it. Just trust me. Come on, there's a brave soldier. Come with me."

"Well, I take it we won't have a problem with it jumping into the circle of its own volition?" said Oz.

"We'll have trouble with him getting anywhere near it," said Paul.

"Okay, if that little pantomime is over, let's get onto the main feature, shall we, people? Paul. You stand there, please, at the base of the pentagram. Ess, you over there. Wonderful. Remember the rules. One final touch."

Oz took a small brass saucer and placed it in the circle. He pulled a Tupperware box from a holdall and carefully poured the thick red liquid into the saucer.

"Is that blood?" asked Ess, wrinkling her nose.

"Relax. I had liver in my fridge," said Oz. "I was going to fry it up with onion gravy tonight. It's one of the reasons I've never asked you to marry me, precious. I could never be a vegetarian. It should be a sacrificial goat, but the principle is sound."

Oz put the tub away, opened the textbook and took his station opposite Ess. "Here we go then. Does anyone want to back out?" He looked hard at each of the others in turn. "Sure? Because after this moment, there's no backing out, and summoning a demon is not exactly risk-free. Okay."

He started to intone from the book, running his finger over the lines. Paul didn't recognise the language. It seemed full of harsh gutturals. He looked over at Ess, who smiled back. It was probably meant to be one of encouragement, but it betrayed her nerves. He was suddenly struck by the huge effort and risk these people had put themselves through, on the basis of less than forty-eight hours acquaintance. If it had been him in their place, would he have put himself out as much? He smiled back, and hoped it showed less anxiety than hers.

Paul didn't know what to expect. A flash, maybe, or a puff of smoke. A gaping hole appearing in the floor, spewing flames, or a rent in the space-time continuum achieved by hugely expensive CGI effects. Instead, an old man suddenly appeared in the centre of the circle, as though he was waiting for the bus.

He stared at Paul for long seconds, then slowly turned his head to take in Oz and Ess. His thin lips stretched into what might have been a smile.

"Good evening," he said.