"They're carrying on to the end of the corridor," Skulduggery said. "There's no way out there. They'll have to double back. You don't have long."

She spun, screwdriver working, twisting and twisting until- "Done," she said, the last screw joining the others on the ground. She dug the screwdriver in at one corner and prised the covering loose, then got her fingers in there. She bit her lip and pulled, ignoring the pain as the metal dug into her skin. It came free all of a sudden and she lifted it away. She looked at the square hole. It was dark, and looked too small to fit in.

"Are you sure I won't get stuck?" she asked.

"You don't have a choice," Skulduggery said. "They're on the way back to you. You're going to be crawling to your left. Move!"

Valkyrie took a deep breath, and plunged in.

t was tight.

It was small and tight and dark. She couldn't even raise herself up on to her hands and knees. She shuffled forward on her elbows.

"See?" Skulduggery said. "I told you you'd be fine."

She kept shuffling until she froze. She closed her eyes, turned her head so she could whisper into the phone. "Get me out of here. It's too small. How am I going to get out? I can't turn around."

"It won't do you any good to panic."

"I'm going to get stuck in here, I know I am."

"Shh. They're in the room behind you."

She quietened. She could hear them, their raised voices, arguing among themselves. One of the voices got suddenly louder, and she twisted to look back. A head appeared in the shaft, examining the space. He couldn't see her, lying there in the dark.

"Valkyrie," Skulduggery said, very softly. "There aren't any cameras in the room. I can't see what they're doing."

She didn't answer. The head ducked back out and the voices started up again. Valkyrie crawled on, as fast and as quietly as she could. There was a series of loud noises behind her.

"They're in here with me," she whispered. "They're following me."

"Just keep going," she heard Skulduggery say. "You're going to pass four more covers like the one you just opened. The fifth one will overlook a stairwell that should be empty. That's where you're getting out."

The first ventilation cover was up ahead. Already her muscles were burning. Her hair fell over her face but she didn't have room, or time, to tie it back. She crawled on, phone in one hand, screwdriver in the other.

The closer she got to the vent, the louder the alarm sounded.

She didn't want to glance back, didn't want to see anyone moving back there. She kept her eyes front, kept her elbows working. She reached the vent and glanced through into a dark room. She moved on. She could hear voices behind but she did her best to block them out.

There was another vent ahead. Light streamed in through the slats. There was some movement outside. People running. She reached the vent and shuffled onwards, but a voice behind her drifted up.

"You see that?" the voice said. "There's someone up there."

She froze.

"No there's not," said another voice. "Just keep going, will you?"

"Just look. See? They were moving just a second ago. Hutchinson, get up here. See that?"

"Yeah," said the third voice, the one they called Hutchinson. "Hey there! Hold on a sec!"

Valkyrie took a deep, deep breath and started crawling again, as fast as she could, without caring about the noise she was making. The men behind her shouted but she couldn't hear the words. She didn't want to hear the words. They were far behind her and there was no way they were going to catch up.

Her muscles burned and she stopped for a moment, heard frantic movement close behind her and glanced back, saw a grinning face moving through the slotted light.

"Hey!"

It was the one called Hutchinson. He was small and thin and squirming through the ventilation shaft like a rat. She started crawling again but it was no use. She felt his grip on her boots and tried to stamp her foot back into his face. His soft chuckle echoed as his hands wrapped round the back of her knees. He hauled himself forward, moving over her kicking legs centimetre by centimetre. He got another handhold, the waistband of her trousers this time. She squirmed, reached behind her and tried to keep him away, but he pushed her hand down and now he was squeezing in on top of her. He wasn't heavy but he was filling every space now, and she couldn't even move her arms.

"It's OK," he whispered as he crawled up her back. "I'm not going to hurt you." She could hear the smile in his voice. He tried to slip his right arm round her throat but she tucked her chin down. His fingers worked beneath her jaw. "It's OK," he whispered. "Shhh..."

He pulled her hair with his free hand, but didn't have the space to make it unbearable. He abandoned that tactic, tried to make her loosen up by jabbing at her, but she kept her chin down. Even so his right hand was getting in there. He was going to get in eventually. She readied the screwdriver.

His hand slipped through and suddenly his arm was round her throat. She jabbed blindly over her shoulder with the screwdriver and he squealed, started thrashing as she heaved herself ahead of him. He didn't try to stop her. He fell against her legs and she grunted, kicking back to shove him off. She'd lost the screwdriver but it had been worth it, and now he was an obstacle to the men crawling behind him.

But his screams had attracted attention. There were shouts from up ahead, and someone started kicking the vent. If they got it open, she'd be trapped.

She stuffed her phone into her jacket pocket, and crawled faster.

The men behind were shouting now, trying to make themselves heard over Hutchinson's screams. And then there was a horrible cracking sound, and the screams stopped. Valkyrie didn't have to look back to know what they'd done.

"Kick it in!" one of them shouted. "She's trying to get by!"

The kicking resumed. Intensified. The covering started to buckle.

Valkyrie reached it, didn't even glance through the slats.

"There she is!" a man shouted. "Get it open!"

Multiple boots, kicking. She got by but the ventilation cover burst open behind her and a man reached in, grabbed her ankle.

"Got her!"

She kicked, kept kicking, kept slamming her heel on to his hand, even as she was hauled backwards. She looked over her shoulder, saw more hands reaching in, grabbing her, and now her feet were out of the duct, and she was dragged out after them.

She slid across the floor, men in prison uniforms staring down at her. She got her legs free and scrambled up, burst through them into the corner of the room then turned, hands clenched, teeth bared. Exhausted, sweating, terrified.

The men formed a semicircle, cutting her off from the open door. Four of them, and now two more crawling out of the duct. All the shouting had ended. All the cursing. Now they looked at her, and she looked at them, and none of them said anything.

One of them, the biggest, started to grin. It started small, then spread across his face. "I haven't killed anyone so pretty in years." He stepped forward.

Another man, a skinhead with facial tattoos, put a hand on his arm. "No," he said. "We use her as a hostage. She's our ticket out of here."

The big man tried to shake the hand off. The skinhead held on. A scuffle broke out, and then a fight, and suddenly all six men were slamming into each other. One of them, a man with yellow teeth, reached for her, grabbed her wrist, and yanked her through the gap he had made.

"Run!" he shouted, and cried out as the big man snapped his neck.

Valkyrie ran, kept running, found herself skirting the top tier of the Observation Deck. Two convicts were sitting against the wall up ahead, just talking, looking like they'd opted out of all the violence going on down below. She ran past them and they stared at her, but didn't try to follow. There was a shout and she glanced back. The big man was coming.

She saw an AUTHORISED PERSONNEL ONLY sign and followed it, sprinting through a narrow corridor that ended with a door. A convict was on his knees by the door, trying to pick the lock. He gave a little cheer and stood up, opened it and turned with a smile on his face that she wiped off with a flying elbow. She didn't even see him crumple to the ground, and now she was in a stairwell, jumping down the steps.

The big man was hurtling down after her.

There were no cameras in the stairwell, but surely Skulduggery had seen where she was heading. She jumped and slammed against the wall, pushed herself off, almost falling down to the next level. Speed was one thing, but if she twisted her ankle trying to get away, she'd never leave this stairwell alive.

She heard the big man stumble and fall, his curses ringing out, giving her a boost of hope. She was going to make it. Five more floors to go before she reached the basement. He was, what, maybe three levels above? She was going to make it. She was going to get to the basement level and burst through the door and Skulduggery was going to be there, gun in hand.

He'd better be.

Valkyrie got to the basement, all cold walls and leaking pipes, flickering lights and gloom stretching into shadows. She lunged out through the door, into a small maze of corridors. Skulduggery wasn't there.

The big man came through the door like a bull and she took off. He was right behind her, and gaining. Valkyrie dodged left so he overshot, then took the adjoining corridor, glancing back to see him stumbling to correct his course. There was a door ahead, marked MAINTENANCE. She ran into the tiny room, slamming the door shut behind her. She spun, planted her left foot forward, her right leg ready. His footsteps and his curses got louder and as he burst in, she was already kicking.

Her boot hit the door, the door hit his head.

Valkyrie fell back from the impact and he dropped to his knees, hands clutching his face. She sprang up, grabbed a mop, smacked the handle on to the top of his skull. He howled, started moving away. She jabbed him in the face with the handle until he knocked it from her hands, and she jumped out after him, swinging kicks into his side. He caught her leg, held it to him as he struggled to his feet. He was panting heavily from the exertion, blood running from his nose. He slammed her back against the wall, one hand still holding her leg, keeping her off balance while the other hand wrapped round her throat.

She went for his eyes, digging her thumbs in. He tried turning his head, then took her violently to the ground. Kneeling between her legs, both hands now at her throat. Unable to breathe, her head suddenly pounding, Valkyrie squirmed into position then turned on to her hip, bringing one leg in to press against him. He pushed forward and she scissor-swept his legs, flipping him on to his back. Now she was on top and she rose up, started raining down palm shots and elbows. Four of them were all she needed, but she kept going, just to be sure. When he sparked out, unconscious and limp, she rolled off, breathing hard.

She forced herself to her feet. Her arms and legs were drained. She couldn't get her breathing under control. She staggered away from him, turned a few more corners before she let herself stop and bend over, hands on her knees, panting. While she was down there, she noticed a series of pipes free of rust or wear. She started following them, all the way to a door.

Once she was breathing properly again, she wiped the sweat from her forehead, and stepped into the room. "Ah," she said. "Found you."

er magic returned to her the moment she set foot in there but she almost didn't notice it, what with the man lying flat in mid-air, suspended off the ground by dozens of cables and wires that stretched taut from his wrists and ankles to the four corners of the room. The cables pulsed with an energy that emanated outwards. The man's eyes were open but unseeing. Some kind of helmet was strapped to his head. Thick bundles of wires cascaded from the back of it, disappearing through a small hole in the floor. Valkyrie stared at Silas Nadir and wondered if he was even aware of what was going on.

The door burst open behind her and Skulduggery ran in, gun in hand. He saw her. Froze. "Are you OK?"

She nodded.

"They didn't hurt you?"

She shook her head.

"The Cleavers are taking back control. The riot has been subdued. The last stragglers are being rounded up. You're sure you're OK?"

"I'm grand. You can probably put your gun away."

He looked at it. "I think I'll keep it out, actually. In case I want to shoot someone. I see you've found the dearly departed Mr Nadir."

"Mien's been using him to shunt the prison through realities. Look at all these wires. The whole place is hooked up to him. It must be awful."

Skulduggery joined her. "Don't forget, the man is a serial killer."

"He still shouldn't be used like this."

"The alternative is to keep him in a cell, being of no use to anyone."

"Are you actually in favour of this?"

"Not at all," Skulduggery said. "But I understand how Mien justified it to himself. Of course, I doubt either of us would be so morally righteous if Nadir had murdered anyone we knew."

"That's not the point," said Valkyrie. "So what do we do now?"

"We unhook him," Skulduggery said, examining the cables. "Hopefully, he'll wake up and we can question him about Lament. Once we have our answer, we throw him back in his old cell."

"Do you know how to unhook him?"

"I'm assuming we just take off the helmet."

"Just like that? Will he be harmed?"

"If we're lucky, it might sting him a little. If we're unlucky, it might cause irreversible brain damage. I'm feeling lucky, though, aren't you? It's a Saturday. Saturdays have always been lucky for us."

"I hadn't noticed. Look, we should probably find someone who knows what they're doing."

"Probably," Skulduggery murmured. "However..."

His gloved fingers skipped lightly over the helmet, then gripped a wire and yanked it from its slot.

Valkyrie's eyes widened. "Are you sure that's a good idea?"

"I think I've worked it out," he said. "I just need to disconnect the Emergency Valve Regulators one at a time. Once that's done, removing the helmet shouldn't result in any significant trauma."

"Emergency Valve Regulators," she repeated. "So you do know what you're doing?"

"Not really," he said, yanking another wire. "I made that term up to keep you happy. I'm just pulling all the red wires because they're the pretty ones."

Before she could protest, he'd yanked another three, then nodded. "That should do it."

"Oh, dear God."

He started undoing the helmet straps. "If this works, you're going to be mightily impressed with me."

"And if it doesn't work, you could kill him."

"For the chance to see the look of sheer awe on your face, Valkyrie, I'm willing to risk it." He removed the helmet and let it fall. Nadir's head lolled back and his eyes closed.

Valkyrie frowned. "When will we know if he's OK?"

"When he wakes up, I should imagine. Help me unstrap him."

They worked together to free Nadir of the wires and cables holding him off the ground, and together they laid him on the floor.

Valkyrie stood quietly for a few seconds, and asked, "Can we wake him now?"

"Patience has never been your strong suit, has it?" He slapped Nadir's face. "Excuse me. Excuse me, could you wake up now, please?"

Nadir moaned, and frowned, and Skulduggery slapped him again. His eyes snapped open and he looked at them, glared at them, and scrambled up.