"And this Accelerator exists?" Skulduggery asked.

"I think so," said Lament. "And I think it's hidden somewhere in Roarhaven. Even if it's half finished, we could work on it, bring it online."

"Why?"

"Because it doesn't have to be used for its original intention," said Lament. "It could be altered, used to charge the Cube indefinitely. Skulduggery, you were talking about increasing the Cube's power by two or three times? The Accelerator would increase it a hundredfold, and we wouldn't even need the Tempest hooked up to it. Argeddion would never wake up, never escape. And if this Darquesse really is as powerful as everyone thinks she will be, she can be held in a Cube alongside him. We're talking about a maximum security prison strong enough to hold gods."

"In that case," Skulduggery said, standing up, "I think it's time I made a phone call."

Valkyrie followed him to an empty room. His phone was in his hand but he didn't dial.

"What do you think?" he asked.

"About what? The idea? I think it's great."

"What do you think of building a prison that could hold you? This isn't theoretical any more if we go down this road, it's a reality. We'll be building a Cube for you, Valkyrie."

She shrugged. "That's what we want, isn't it?"

He folded his arms. "Are you really going to stand there and tell me this whole thing doesn't scare you?"

She laughed. "What do you want me to say? 'Don't build a Cube for me?' Then what? I kill everyone?"

"All I want you to do is admit how you feel."

"What good is that going to do us?"

"You need to be absolutely sure about your motivations for going along with this."

"So you want me to be honest? Because the two of us have always been really good with honesty, yeah? Because we've never hidden the truth from anyone? You know what? Fine. I don't want a prison built for me, OK? I don't want to sleep for an eternity in a Cube. I want to be free and stay free and be happy and alive. But I'm not going to get that chance."

"We don't know that yet."

"Of course we do. My God, every time I give in and Darquesse comes out things start making sense. Nothing scares me and nothing worries me. I'm pure. I'm content. Do you know how wonderful that is? To feel that? And the more it happens, the harder it is to push it back down again. I... I like being Darquesse. I think I might like it even more than I like being me."

They looked at each other for the longest time, and then he took a single step and hugged her. He was cold and bony, but when she rested her head against his sternum, that didn't matter.

"Of course you do," he said softly.

She stepped back. "What?"

"I told you," he said. "Power is addictive. Why wouldn't you love being that strong? Why wouldn't you love being able to bring yourself back from the brink of death?"

"It's not just that. It's the way I'm starting to think. It's the thoughts I have. I don't even realise I'm thinking them and then suddenly it hits me. It's not that Darquesse is taking over, it's... It's that I'm becoming more like her with every single day that passes. I don't want to spend the rest of my life in a Cube, Skulduggery, of course I don't. But we need it. We need to build it."

"OK then," he said. "Just as long as we're both ready to admit what it might mean." He dialled a number, put the call on speaker.

"Finally!" Ghastly said when he answered. "You do remember I asked you to call in every four hours, yes? And that was twenty hours ago?"

"I was going to call," Skulduggery replied, "but I was too busy being brilliant. Tyren Lament says hello, by the way."

"They're all there?"

"All four of them, in a secret base built into the side of a mountain. You'd love it. It's very James Bond."

"And Argeddion? He's alive?"

"He's being kept in an artificially induced coma, yes. There might be a way to reinforce the cage that's holding him, which should cut off whatever influence he's having on the world. But in order to do this, we need another machine located somewhere in Roarhaven. Probably in the Sanctuary itself."

"What is it?"

"It's called the Accelerator. I'll send you a file as soon as I have one, just to let you know what you're looking for. It was part of the Roarhaven coup attempt, so it's probably well hidden. It might not be wise to involve any Roarhaven mages in the search for it or, in fact, any other mages at all, apart from Ravel."

"You're sounding awfully paranoid."

"I have reason to be. In the wrong hands, the Accelerator could be the most devastating weapon the world has ever seen."

rand Mage, Elder Bespoke, I was wondering if I could have a word."

Ravel talked as he walked. "You, Mr Sult? Are we no longer important enough to warrant direct communication with Grand Mage Strom? Instead, they send a Junior Administrator to speak to us?"

"We'd almost be offended if we cared," said Ghastly.

"My deepest apologies," Sult responded. "I assure you, we mean no disrespect. It's just, with the murder of Christophe Nocturnal in this very building, Grand Mage Strom has been advised to move to a more... secure location. But I am fully authorised to speak on behalf of the whole Supreme Council on all matters."

"They left you behind, then?" Ravel said. "They must really like you, to leave you in such dangerous territory."

Sult smiled politely. "They have faith that I will be well protected by your Cleavers and operatives, all of whom are beyond reproach in their duties. Personally, I do not feel in danger in the slightest."

Ghastly glanced at Ravel, and stopped walking. Sult almost collided with him, then backed off with a chuckle as Ravel kept going. Ghastly looked him in the eye. "What can I do for you, Mr Sult?"

"Ah, yes, to business. It has come to my attention, Elder Bespoke, that there has been some tension arising between our people and yours."

"You mean the fight that broke out last night."

"Yes, sir, I do. I wish to apologise on behalf of the Supreme Council. It is not our intention to make trouble."

"OK."

"However, the incident has resulted in three of our operatives needing medical attention."

"And two of ours."

"Yes, sir, but, without wishing to offend, it was your men who started the fight."

"That's not how I heard it."

Sult smiled. "I have no wish to contradict you, sir. But we have our report, in which a verbal disagreement escalated into a physical confrontation when one of your men punched the leader of our security team."

"Who had been making some pretty derogatory remarks."

"For which he will be disciplined. However, a verbal assault and a physical assault are completely different things."

"They're both assaults, are they not?"

"Yes, sir, but-"

"And a physical assault is usually preceded by a verbal assault, and our people are trained to spot this and act accordingly. So while my man may have thrown the first punch, he did not actually start the fight. That was your man."

"Elder Bespoke-"

"Mr Sult, I have neither the time nor the inclination to stand here and argue this with you. Your guys had a fight with my guys. That's it. It happens, and that's the end of it. But if it happens again, we'll be kicking your guys out of the country."

"What? You can't be serious."

"Tempers are frayed. Patience is short. We have a huge problem that we're trying to deal with and a prisoner has been murdered while in our custody. I don't care about a fight in which nobody was seriously injured, and neither should you. There are other things to worry about. Give my regards to your bosses."

Ghastly walked away. Sult, to his credit, didn't even try to follow.

Ravel was waiting around the next corner. "Thanks," he said. "I really don't like that guy."

They took the stairs to the lower levels. Cleavers stood to attention when they passed. The corridors got darker and colder and Ghastly had to take out a map to keep track of where they were going.

"Isn't this beneath us?" Ravel asked as they walked. "This is probably beneath us. We're Elders. We're not supposed to look for things. We're supposed to get things handed to us."

"It amazes me how quickly you've become spoiled."

"I never liked looking for things," Ravel grumbled. "You remember looking for clues with Skulduggery? I always hated that. I never knew what was a clue and what wasn't. I'd look at a room and see a room and he'd look at it and solve a mystery."

"I wouldn't worry about it," said Ghastly. "You might not be as good a detective as Skulduggery is, but you're good at other things. Like wearing a robe and complaining."

"I'm amazing at those things," Ravel said. "And I order people around really well. This morning, Tipstaff came over with a cup of tea and I told him no, I don't want tea I want coffee. That was great. I really asserted my authority."

"Did he go and get you a coffee?"

"No, he said he'd already made a pot of tea so I took the tea because, you know, he'd already made it, but my authority was still firmly asserted."

Ghastly nodded. "He'll think twice before making tea again."

"That he will, Ghastly my friend, that he will. What are we looking for, by the way?"

"Seriously? I gave you the file half an hour ago."

"Yes, you did."

"Did you read it?"

"No, I did not."

Ghastly sighed. "It's called an Accelerator. It's a big machine type thing."

"Great. What does it look like?"

"I don't know."

"Is that it?"

"No. That's a wall."

"It could be disguised."

"You're really not very good at looking for things, are you?"

"I'm good at looking for walls. Look, I found another one."

They came to a junction and Ghastly stopped walking, and frowned. "This is odd. That corridor isn't on the map."

Ravel folded his arms. "Maybe it isn't there."

"Maybe the corridor isn't there?"

"Maybe it's an optical illusion. Or it's like Schrodinger's cat. Until you look at it, it's both there and not there."

"But we're looking at it now, Erskine, and I'm pretty sure it's there. It just isn't on the map."

Ravel shrugged. "It's an old building. There are tunnels and secret passageways all over the place."

"But the first thing we did when we moved the Sanctuary was send a team of mages down here to check for things like this. I'm holding the map they made."

Ravel looked at him. "We sent a team of Roarhaven mages."

"They left out this corridor on purpose," Ghastly said, putting the map away. "Skulduggery was right. We can't trust them. So what's down here that they wanted to keep secret?"

"Hopefully, it's the Accelerator, and not just some bathroom they wanted to keep private. We should probably get a squad of Cleavers to go down first, make sure it's safe and clear of booby traps."

"Yeah," said Ghastly. "We probably should. We could go back up and sit on our thrones and drink tea while we wait."

"Good idea. Safe, too. Tipstaff would approve."

"He really would," said Ghastly, and they both started down the corridor.

They found a series of rooms without doors. Those that weren't empty were stacked with building materials and supplies, and a thick layer of dust covered everything. The power down there hadn't been connected, so they each held fire in their hands to light their way. Rats scuttled in corners and water dripped into large, cold puddles, and the shadows played as they walked. Ravel stopped.

"I think I've found it," he said.

They stepped into a large room. Most of it was empty space, as dark and as damp as the corridor outside. The Accelerator stood in the exact centre like a giant vase that had burst open from within. Its curved wall bent gently back, the jagged tips almost scraping the ceiling. The front section was open, allowing access into the thing itself, where a white disc rested on its base, forming a slightly raised platform. Circuitry ran like dull veins through the skin of the machine, which seemed almost translucent under the flickering firelight.

Ravel knocked his fist against it. The sound suggested a strange mixture of metal and rubber. Ghastly stepped through the opening, on to the white dais. Hemmed in on three sides, he got an odd feeling of claustrophobia.