Inside the Palace, unaware of the events silently unfolding around her, Sarah Heap was perched precariously at the top of a stepladder in the Palace entrance hall. By the light of a beautiful chandelier (it had taken Billy Pot ten whole minutes to light all of its candles) Sarah was busy nailing up a banner that read HAPPY 14TH BIRTHDAY JENNA AND SEPTIMUS above the archway that led into the Long Walk. She was not pleased to hear the sound of approaching footsteps outside.

"Botheration," Sarah muttered under her breath. She knew that one set of footsteps belonged to Marcia Overstrand - somehow Marcia always managed to walk everywhere as though she owned the place. Sarah struggled irritably with the unwieldy banner above her head. Trust Marcia to arrive early, she thought. Well, she would have to make herself useful until the party started. Goodness knows there was plenty to do. Oops. She could hold the stepladder steady for a start.

The sound of the footsteps changed from cinder scrunches on the path to purposeful tippy-taps of purple python on wood as they crossed the bridge over the ornamental moat. They were followed by equally purposeful - but less proprietary - thuds of the footsteps of Marcia's companions.

The Palace doors were pushed open and the tippy-taps strode across the stone floor of the entrance hall. They halted below Sarah's ladder.

"Sarah Heap," Marcia announced.

Why, Sarah wondered crossly, did Marcia have to sound so officious? She turned around, hammer raised, the last two nails held between her lips.

"Mrgh?" said Sarah, finally deigning to look down at her visitors. "Ah, hrr Brrr n Hrrrr," she said, actually pleased to see two of Marcia's companions, Beetle and Hildegarde, although less pleased to see the young witch they had with them. She took the nails out of her mouth. "You're early," she said. "But I could do with some help. There's always more to do than you think to get a party ready."

"Mum," said the young witch.

Sarah nearly dropped her hammer. "Goodness, Jenna. It's you. I didn't know this was going to be a fancy dress party."

"Mum, it's not, but - " Jenna began, wanting to explain before Marcia jumped in with both feet.

Sarah looked disapproving. "Well, I don't know why you are walking around in that witch stuff," she said. "You really shouldn't. It's not nice."

"Sorry. It's been a bit of a rush. But - "

"You're telling me. We're not nearly ready for the party, and now - "

"Mum, listen - "

"The party's cancelled," said Marcia.

Sarah dropped the hammer, narrowly missing Marcia's right foot. "What?" she said angrily.

"Canceled. You and everyone inside the Palace have five minutes to leave."

Sarah was down the ladder in a flash. "Marcia Overstrand, how dare you?"

"Mum," said Jenna. "Please listen, it's important, something has - "

"Thank you, Jenna, I'll handle this," said Marcia. "Sarah, it is my job to ensure the safety of the Palace. There's a Cordon encircling the building and I am now putting it in Quarantine."

Sarah looked exasperated. "Look here, Marcia, there is no need to go to such extremes. I don't know what Septimus or Jenna have been telling you about the party, but you really mustn't take any notice. Their father and I will be here and we have no intention of letting things get out of hand."

"It seems they already have got out of hand, Sarah," said Marcia. She put her hand up to stop Sarah's protests. "Sarah, listen to me, I am not talking about the party. And may I say, the fact that you and Silas have been here appears to have been no safeguard against anything whatsoever. Indeed, I am surprised - and not a little disappointed - that Silas has allowed this to happen."

"It's only a little birthday party, Marcia," Sarah said snappily. "Of course we've allowed it to happen."

"Sarah, for goodness' sake, listen to what I am saying. I am not talking about the birthday party," Marcia replied, equally snappily. "And you can stop waving that hammer around too."

Sarah looked at the hammer in her hand as though she was surprised to find it there. She shrugged and placed it on the stepladder.

"Thank you," said Marcia.

"So what are you talking about?" Sarah demanded.

"I am talking about your lodger in the attic."

"What lodger? We don't have lodgers," Sarah said indignantly. "Things may be a bit tough sometimes but we haven't had to rent the Palace out as a guesthouse quite yet. And even if we did, I hardly think we need your permission, thank you very much." Sarah folded up the stepladder with an angry bang and began to heave it into the Long Walk. Beetle stepped forward and took it from her.

"Thank you, Beetle," said Sarah, "that's very sweet of you. Excuse me, Marcia, I have things to do." With that she began gathering up the remains of streamers that were scattered across the floor.

"Mum," said Jenna, handing her some fallen streamers. "Mum, please. There's something horrible here. We have to - "

But Sarah was not in a mood to listen. "And you can take that witch cloak off right now, Jenna. It smells awful - just like the real thing."

Marcia raised her voice. "This is my final warning. I am about to Quarantine this building." She got out her timepiece and laid it on her palm. "You have five minutes from now to vacate the premises."

This was too much for Sarah. She stood up and, hands on hips, hair angrily awry, she raised her voice even louder. "Now look here, Marcia Overstrand, I have had quite enough of you barging in on my daughter's birthday - and my son's too, as it happens - and tearing everything apart. I will thank you to go away and leave us in peace."

Hildegarde had been watching Marcia's handling of the proceedings with dismay. Before her promotion to the Wizard Tower, Hildegarde had been on door duty at the Palace. She knew Sarah Heap well and she liked her a lot. Hildegarde stepped forward and laid her hand on Sarah's arm.

"Sarah, I'm very sorry, but this is extremely serious," she said. "There really is someone in your attic and he has, so it seems, set up a Darke Domaine in there. Madam Marcia has placed a protective Cordon around the Palace to prevent the Domaine escaping and now, for the safety of all of us in the Castle, she needs to place the Palace in Quarantine. I'm so sorry this had to happen today of all days, but we dare not leave it a moment longer. You do understand, don't you?"

Sarah stared at Hildegarde in disbelief. She wiped a hand across her forehead and sank into a battered old armchair. A faint groan came from the chair, and Sarah sprang to her feet. "Oh, sorry, Godric," she said, apologizing to the very faded ghost who had fallen asleep in the chair some years ago. The ghost slept on.

"Is this true?" Sarah asked Marcia.

"That's what I've been trying to tell you, if only you'd listen."

"You haven't been trying to tell me anything," Sarah pointed out. "You have been issuing instructions. As usual." She looked around, worried. "Where's Silas?"

Her question was answered by the sound of running footsteps above. Silas Heap, blue Ordinary Wizard robes flying as, two at a time, he raced down the sweeping stairs that led down to the entrance hall was yelling, "Everyone - get out, get out!"

Silas skidded to a halt at the foot of the stairs and, for the first time in his life, he looked pleased to see Marcia. "Marcia," he puffed. "Oh, thank goodness you're here. My SafetyGate has been broken. It's got out of the attic. It's upstairs now and it's filling the place up - fast. We've got to get a Quarantine put on. Marcia, you need to do a Call Out, get a Cordon around if we've got time - "

"All done," Marcia told Silas briskly. "The Cordon of Wizards is in position."

Silas was stunned into silence.

Marcia got down to business. "Is there anyone else in the Palace?"

Sarah shook her head. "Snorri and her mother have gone off on their boat. The Pots have gone to see the lights. Maizie's out lighting up, Cook's gone home with a cold, and no one's arrived for the party yet."

"Good," said Marcia. She glanced up to the top of the wide flight of stairs, which led to a gallery from which the upstairs corridor ran the length of the Palace. Along the gallery, the rushlights were burning as usual, but the dimming of the light where the corridor stretched away both to the left and right told Marcia that the more distant lights were being extinguished. The Darke Domaine was getting closer.

"Everyone will exit the premises," she said. "Now!"

"Ethel!" gasped Sarah. She raced off and disappeared into the Long Walk.

"Ethel? Who on earth is Ethel?" Marcia glanced up to the gallery. The flame on the farthest rushlight began to dim.

"Ethel's a duck," said Silas.

"A duck?"

But Silas was gone, racing off in pursuit of Sarah - and Maxie, who he just remembered he had left sitting by the fire that morning.

Up on the gallery the first rushlight had gone out and the flame on a second, nearer rushlight was faltering. Marcia looked at Jenna, Beetle and Hildegarde. "It's moving fast. If I don't do the Quarantine now, this is going to get out. And frankly, I am not sure that our Cordon will hold it. We are very widely spaced. And I certainly won't have time to Raise a Safety Curtain."

"You can't leave Mum and Dad," gasped Jenna.

"I have no choice. They're putting the whole Castle at risk - for a duck."

"You can't do that! I'm going to go and get them." With that Jenna raced off. Hildegarde darted after her and grabbed her witch's cloak.

Jenna spun around angrily. "Let go!"

The cloak felt horrible to the touch, but Hildegarde doggedly hung on. "No, Princess Jenna, you mustn't go. It's too risky. I'll go. They'll be in Sarah's sitting room, yes?"

Jenna nodded. "Yes, but - "

"I'll get them out of the window." Hildegarde glanced at Marcia, calculating how long it would take to get to Sarah's sitting room. "Give me . . . count me to a hundred and then do it. Okay?"

Marcia looked up at the landing. A wall of darkness now blocked any view of the corridors. She shook her head. "Seventy-five."

Hildegarde gulped. "Okay. Seventy-five." And she was gone.

"One," began Marcia. "Two, three, four . . ." She signed to Beetle and Jenna to leave. Jenna shook her head.

Beetle took Jenna's arm. "You must leave," he said. "Your parents would not want you to stay. Hildegarde will get them out."

"No. I can't go without Mum and Dad."

"Jenna, you have to. You are the Princess. You must be safe."

"I'm sick of being safe," she hissed.

But Beetle backed out of the Palace doors, taking Jenna with him. Once outside he took a small, fat tube from his pocket. "I've got the Flare," he called to Marcia.

Marcia gave him a thumbs-up. "Thirty-five, thirty-six . . ."

"What Flare?" asked Jenna.

"To Activate the Cordon. Just in case."

"In case what?"

"Well, in case the Quarantine doesn't work. In case something escapes."

"Like Mum and Dad, you mean?" Jenna said, wrenching her arm from Beetle's grasp.

"No. In case something Darke escapes."

But Jenna was not there to hear. Witch cloak flying, she was racing off along the small path that ran around to the back of the Palace. Beetle sighed. He wished Jenna would take off the witch cloak. She didn't seem like Jenna anymore.

Feeling wretched, Beetle waited between the two burning torches on either side of the bridge. Through the open Palace doors he saw the pile of abandoned birthday presents, the discarded streamers, the HAPPY BIRTHDAY banner, all looking oddly out of place now as Marcia - purple robed and intense - paced back and forth, continuing her count. Beetle saw the last rushlight at the top of the stairs flicker and go out and the wall of Darkenesse - not nighttime darkness but something thicker, more solid - begin to move down toward the pacing figure below.

Beetle watched Marcia like a hawk, terrified of missing her signal. The ExtraOrdinary Wizard was backing toward the door now. She was still counting, going on for as long as she dared in order to give Hildegarde the best possible chance.

"One hundred and four, one hundred and five . . ."

With every step backwards that Marcia took, the Darkenesse advanced. It reminded Beetle of a giant cider press he had once visited where you could stand inside and watch the pressing plate move down toward you. It had terrified Beetle at the time - and now it terrified him all over again.

The descending roof of Darkenesse reached the chandelier, and suddenly all the candles sputtered out. Beetle saw Marcia raise her right hand. He pushed the Ignite pin into the side of the Flare, held the Flare at arm's length and was blown off his feet by the sudden blast of light that shot into the sky. A gasp of "oohs" came from the crowd beyond, but from the Cordon came the quieter sound of a sustained humming, as though the Palace were surrounded by a gigantic swarm of bees. The Cordon was now Active. Marcia leaped outside, slammed the thick wooden doors shut, laid a hand on each door and began the Quarantine.

The Magyk was so strong that even Beetle - who was not a very Magykal person - could see the purple shimmering haze of Magyk playing around the doors and, as sound of the humming from the huge circle of Wizards, Apprentices and scribes filled the air, the Magyk spread out from the doors, creeping across the darkened windows of the Palace, Quarantining everything that lay within in a thin veil of purple.

Beetle hoped that what lay within did not include Hildegarde, Sarah and Silas. Or Jenna.