Beetle," said Marcia as they halted outside Larry's Dead Languages and Beetle fumbled for his key. "What are your plans for tonight?"

Beetle thought glumly what his plans had been: Jenna's fourteenth-birthday party at the Palace. He'd been looking forward to it for months. He knew that the cancellation of a party paled in significance against what had happened at the Palace that night, but if you'd asked Beetle which he regretted most right then, he would have admitted it was the party.

"None," he replied.

"In the continued absence of my Apprentice" - there was an edge in Marcia's voice - "I would greatly appreciate an assistant - a knowledgeable assistant. An assistant who does not run off and spend his valuable time with a disreputable old Alchemist." Marcia almost spat the last few words. She recovered her poise and continued. "So, Beetle, what do you say to spending the night at the Wizard Tower and helping us with our preparations for the Fumigation tomorrow?"

Once again Beetle had the uncomfortable feeling of being second choice to an unavailable Septimus. But the offer was not one he wanted to refuse. The alternative was creeping up to his tiny room at the back of Larry's Dead Languages while trying not to wake the irascible Larry - something he had not yet managed to do. Larry was a light sleeper and always woke with a string of Latin curses, which, with his recently acquired knowledge, Beetle now understood perfectly.

And so he replied, "Yes, I'd like that very much."

"Good." Marcia looked pleased.

As Beetle and Marcia walked up Wizard Way, the Safety Curtain lighting up the night behind them, both were occupied with thoughts of who might be marooned in the Palace inside the Darke Domaine. Beetle's thoughts led to his terrifying afternoon - and it was only then he remembered the book he had snatched from Merrin's grasp.

He fished it out of his pocket and handed it to Marcia. "I forgot. Merrin had this. I snatched it just as he was doing the BeGone. I'm sure you've got a copy but I thought you'd be interested."

Marcia stopped in her tracks, which happened to be under a torch post. She stared at the unprepossessing, sticky little book in her hands and let out a long, low whistle. Beetle was a little shocked - he didn't know Marcia whistled.

"Beetle, I most certainly do not have a copy - there is only one of these," said Marcia, turning over the dog-eared book in amazement. "I have wanted to get my hands on this for years. It is the index - the key to the secrets - of a very important book." She looked at Beetle, her eyes shining with excitement. "Beetle, I cannot tell you what a relief this is. I have to confess that what I saw at the Palace tonight frightened me and frankly, I wasn't at all sure we could get rid of it. I was afraid we might never be able to use the Palace again - that it would be Quarantined forever." Marcia shook her head in dismay.

Quickly Marcia flicked through The Darke Index. "Amazing . . . just wonderful. This is the real thing. Beetle - you have saved the day!"

Beetle grinned. "Gosh," he said. "I didn't realize it was that important."

Marcia turned to him. "It is pivotal. You see, now - for the first time for hundreds of years - we can use the Paired Codes. They are our protection against the Darke but we have been unable to read them ever since this disappeared along with The Undoing of the Darkenesse. I found that moldering in the Marram Marshes, but it's no good for the really important stuff without this." She waved The Darke Index triumphantly. "Now we shall be able to get rid of that nasty little concoction of Merrin Meredith's down at the Palace with no trouble at all!" Marcia looked at Beetle with a broad smile. "I do hope it will be all right if I borrow this tonight?"

Beetle was quite taken aback. "Oh . . . yes. Of course," he said. "In fact, I'd like you to keep it. Something like that should only belong to the ExtraOrdinary Wizard."

"Very true," said Marcia approvingly. "But thank you all the same, Beetle." She put The Darke Index into her most secure pocket. "So now," she said, "we shall pay a visit to the Manuscriptorium. There is something there I need to collect."

Bother, thought Beetle.

The door to the Manuscriptorium was locked but Marcia had a key. This was a source of great indignation to Jillie Djinn but there was nothing she could do about it. ExtraOrdinary Wizards always had a key to the Manuscriptorium for use in emergencies - which Marcia considered this to be. She turned the key in the unwilling lock and the door swung open without the usual ping. The counter was disconnected every evening before the scribes left the building.

Reluctantly Beetle followed Marcia into the scruffy front office. He had been there too many times that day for his liking.

"It's not my favorite place, either," Marcia said in a half whisper. "But I need to collect the Manuscriptorium half of the Paired Code. Of course we have the Wizard Tower half of the Pair, but unfortunately the Manuscriptorium half is somewhere here in a place known only to the Chief Hermetic Scribe." Marcia sighed. "I just wish it wasn't this Chief Hermetic Scribe, that's all." She looked at Beetle hopefully. "I don't suppose you happen to know where it might be?" she asked.

Beetle shook his head. "I've no idea what a Paired Code even looks like," he said.

"The Manuscriptorium one is a small silver disc with lines radiating out. I think there's a hole in the middle where the ancient Hermetic Scribes used to put a thread and wear it around their neck. They used the Paired Codes a lot in those days," Marcia said wistfully. "The Manuscriptorium half is much smaller than the Wizard Tower half, which we have up in the Pyramid Library. Neither of them look like much on their own, but when you put them together it's quite something, apparently. As we will soon find out." Marcia looked delighted. The thought of once more being able to perform such ancient Magyk thrilled her.

They went through to the Manuscriptorium, which was deserted. It was wreathed in shadows, illuminated only by the light that shone up from the basement where the Conservation, Preservation and Protection Scribe, Ephaniah Grebe, lived and worked. Of Jillie Djinn there was no sign.

"Miss Djinn will be in her rooms," Beetle whispered to Marcia. "She never stays down here after the scribes have gone home. She goes upstairs and eats biscuits. And counts things."

Beetle led Marcia through the lines of desks to the back of the Manuscriptorium to a short flight of worn stairs with a battered blue door at the top. Marcia tippy-tapped up the stairs and tugged irritably at the silver bellpull beside the door. The faraway tinkle of a bell rang forlornly somewhere at the top of the building. They waited for the sound of Jillie Djinn's footsteps descending, but none came. Impatiently Marcia rang the bell again. There was no response.

"It really is too bad," muttered Marcia. "The Chief Hermetic Scribe should always be available in emergencies." She stomped back down the steps. "We'll just have to search this wretched place until we find her. She's got to be here somewhere."

Suddenly something caught Marcia's attention. She pointed to the narrow stone arch at the side of the Manuscriptorium that led to the Hermetic Chamber. "I thought I saw someone go in. Out of the corner of my eye. But she must have seen us - what is she playing at?" Marcia hurried over, her python shoes tapping on the old oak floorboards.

Beetle hung back as Marcia stepped through the arch into the pitch-black passageway that led to the Chamber, but she beckoned him to come with her. He followed her in.

The Hermetic Chamber, the inner sanctum of the Manuscriptorium, was reached by a seven-cornered passage, which was specially designed to catch any stray Magyk that might try to escape from the Chamber or, indeed, enter and disturb the delicate balance within. It was also completely light tight and soundproof - and somewhat unnerving.

As Beetle followed the rustle of Marcia's cloak brushing along the stone floor of the passageway, he had the uncomfortable feeling from the way she had slowed down that she was a little spooked. As he went deeper into the passage and lost any glimmer of light, Beetle began to feel pretty spooked himself, but as they turned the seventh and last corner, the light from the Hermetic Chamber flooded the final few feet of the passageway and Beetle relaxed. Half obscured by Marcia's flowing cloak, he saw with some relief - for he'd had the distinct impression that Marcia had been expecting something altogether different - the Chief Hermetic Scribe, Jillie Djinn, sitting at the familiar round table.

The white walls of the Hermetic Chamber made it feel dazzling after the darkness of the passageway. Beetle glanced around - everything looked just as he remembered it. The ancient dark Glass was propped up against the roughly plastered walls, as was the old-fashioned abacus. The large, round table was in the middle and underneath it, Jillie Djinn's tiny feet in their sensible - and sadly scuffed - black lace-ups were resting on the main Ice Tunnel hatch, which, Beetle noticed with relief, was closed and clearly had been for a long time, judging by the dust covering it.

Jillie Djinn seemed smaller than Beetle remembered. The harsh light in the Chamber showed up the shabbiness of her dark blue silk robes - a shabbiness that he had not seen before. Jillie Djinn had always been rather fond of new silk robes and was very particular about keeping them clean, but now they were creased and had what looked suspiciously like gravy stains down the front. Beetle was shocked. But what he found most concerning was that Jillie Djinn was not actually doing anything. There were no books of calculating tables open in front of her, no fat ledgers filled with endless columns of her tiny figures, ready for an unfortunate scribe to transcribe in triplicate the next day. She sat hunched over the bare table, staring into space and hardly seemed to register the intrusion of her visitors. It was as if she wasn't there.

A flash of concern crossed Marcia's face but she got straight down to business. "Miss Djinn," she said briskly. "I have come to collect the Manuscriptorium half of the Paired Code."

Jillie Djinn sniffed and, to Beetle's shock, wiped her nose on her sleeve. But she did not reply.

"Miss Djinn," said Marcia, "this is a serious matter. You must make available to the ExtraOrdinary Wizard the Manuscriptorium half of the Paired Code upon request at any time of day or night. I realize this has not been requested for many hundreds of years, but I am requesting it now."

Jillie Djinn did not react. It was as if she did not understand a word that was said.

Marcia looked concerned. "Miss Djinn," she said quietly. "May I remind you that Paired Code Protocol forms part of the induction Oath of a Chief Hermetic Scribe."

Jillie Djinn shifted uncomfortably and sniffed again. She looked pathetic, thought Beetle. Once so upright and proper, she was now weighed down by her cares. He had never liked the Chief Hermetic Scribe, but now his dislike was mixed with sadness for her. And disquiet - something was very wrong. Beetle glanced at Marcia. She was regarding the Chief Hermetic Scribe with a new light in her eye - like a cat getting ready to pounce. And then, suddenly, she did. Marcia leaped forward and clapped both hands on Jillie Djinn's shoulders. "Depart!" she commanded. A flash of purple lit up the white chamber and Jillie Djinn gave a sharp scream. A loud hiss came from beneath Marcia's hands, and Beetle was aware of something small and dark - he couldn't see exactly what - leaping to the ground and scuttling out.

"A Maund," muttered Marcia. "Someone's put a Maund on her. Vicious beasts and so heavy. What is going on here?" She glanced around the Hermetic Chamber anxiously. So did Beetle. It appeared to be empty, but he was no longer so sure.

"Miss Djinn," said Marcia quickly. "This is of the utmost urgency. You must immediately give me the Paired Code."

Jillie Djinn, relieved of her burden, was no longer hunched. But she still looked haunted. She glanced around the chamber, then quickly ran her hand across the table in a zigzag movement. There was a quiet whirring noise and a tiny drawer opened in front of her. Looking about her uneasily, Jillie Djinn took out a small, polished silver box and placed it on the desk.

"Thank you, Miss Djinn," said Marcia. "I would like to check that the Code is indeed in the box."

Jillie Djinn was gazing out somewhere in the distance over Marcia's shoulder. She nodded absently, then an expression of fright flashed across her features.

Marcia was busy opening the box. Inside she saw a small silver disc with a raised central boss, which was exactly like the textbook drawing that she was familiar with. Marcia put her spectacles on and took a closer look. A mass of fine lines radiated from the tiny hole at the center of the disc and scattered along these was an array of Magykal symbols, some of which she had not seen since her advanced codacology week in her final Apprentice year. Marcia was satisfied - it was indeed the Manuscriptorium half of the Paired Code.

There was sudden disturbance in the air. Marcia spun around. She lunged forward, and Beetle saw the little silver disc fly into the air and disappear - then something gave him a sharp punch in the stomach.

"Oof!" He doubled over, gasping for breath.

"Beetle, block the passageway!" Marcia shouted.

Still winded, Beetle threw himself in front of the entrance to the seven-cornered passage. Something bony with sharp elbows hurtled into him and Beetle staggered back. He braced himself, arms across both sides of the narrow passageway so that whatever it was could not pass. As an invisible hand gripped his arm and tried to wrench it away from the wall, Beetle felt something burning dig deep into his flesh.

"Aargh!" he gasped.

"Don't move, Beetle," said Marcia, advancing toward him. "Just . . . stay . . . there."

Beetle's arm felt as though the pointed end of a red-hot stick was being thrust into it, and the look on Marcia's face as she came forward was terrifying. But he did not move. Marcia stopped a little way in front of him, her green eyes flashing furiously. She stretched out her arms and grasped something, as though she were picking up a two-handled pot.

"Reveal!" she said triumphantly. A cloud of purple filled the exit to the Hermetic Chamber and showed a dark shape within it. As the cloud cleared, the gangly form of Merrin Meredith was Revealed, both ears held firmly in Marcia's iron grip.

Merrin swallowed hard and winced. The Paired Code had sharp edges.

"He's swallowed it!" Marcia cried incredulously.