'Then I think we may have found our way into the underworld,' Aubrey said.
'What makes you say that?' Caroline asked. She took an unruly strand of hair that was plastered against her temple and, with both hands, fixed it behind her head.
'When I thumped the door, I felt a magic residue. A familiar one.'
Caroline narrowed her eyes. 'Concentrated on the area near the lock, I assume?'
'Dr Tremaine?' George said. He raised his fists, as if he thought Tremaine was going to burst through the door at any minute.
'Correct, both of you. It's the same security spell he used on the Old Man of Albion, and the tunneller.'
'So I missed him,' Caroline said flatly. She clenched her fists.
'Maybe not,' Aubrey said. 'Tremaine is . . . I don't know . . . not like normal people?'
George rubbed his chin. 'Are you saying like one of those werewolves in the stories? Do we need a silver bullet to finish him off?'
'No, nothing like that. It's just that things that would stop an ordinary person won't stop him.'
'I see,' Caroline said and Aubrey knew that she was taking careful note of this information. It wouldn't make her give up her quest for revenge – it would just make her more careful to do it properly next time.
'He's down there,' Aubrey said, 'so it's time for some ifs.' He counted them on his fingers. 'If it's Tremaine, and if he managed to escape from the Bank of Albion and find somewhere to recover, and if he's still down there, then he'd suspect that his security spell was compromised. He'd change his password.'
'So we're stuck?' George said.
'Maybe not. I might have an idea about a replacement password.'
He spread his left hand on the metal, just above where the bolt slid home. He felt the tingle of magic and had no doubt that it was Dr Tremaine's. 'This has been set recently. Within the last twenty-four hours.'
He ignored Caroline's sharp, hissing intake of breath.
'Sister,' he said, clearly and carefully.
The lock didn't budge.
'Sylvia.'
Nothing.
He chewed his lip, then had an inspiration. 'Pearl,' he said, and the lock's tumblers ticked, clicked, shifted. The bolt slid back and, with grim satisfaction, Aubrey realised that he may have found his enemy's weak spot.
He wrenched the door open and was greeted with a welcome gust of cool air. 'Journey with me,' he said grandly, 'to the centre of the earth.'
Without a word, Caroline stepped through. George followed, mumbling, 'I hope we don't have to go that far.'
Aubrey took a moment to prop the door open with a few bricks, then darted after his friends.
The stairwell was poorly lit. Mechanical noises echoed along its brick walls – clanking, vibrating sounds that made Aubrey think of clockwork toys run amok – but toys the size of buildings. By the time they reached the bottom of the stairs, his knees and calves were aching, but the pounding of his heart didn't come from exertion. His whole body was gripped by tension as they approached their destination, and – not for the first time – he wondered what foolishness had prompted him to plunge into the unknown like this.
Next time, he thought, I'm going to have a crack squad of magical operatives, sappers and marksmen with me. As a bare minimum.
He hoped there would be a next time.
In the lead, Caroline held up a hand and they stopped. The light that fell on her face made her look heartbreakingly beautiful and determined. She beckoned them forward and slipped out of the doorway.
Aubrey followed, then the outrageousness of the scene struck him. All his breath ran out in a single, awed exhalation.
The chamber was vast, the ceiling soaring cathedral-like overhead. The walls to the right and left were thirty or forty yards away but he couldn't make out the far wall, for the chamber was almost choked with a dizzyingly tangled meshwork of chains, cables and conduits. Pipes and wires of a thousand different sizes and colours emerged from the walls, floor and ceiling and dived into the central snarl, a tangled interweaving that defied the eye to unravel it. Plumes of steam gushed from its depths, and it vibrated, rattled, throbbed, hummed and pulsed with enough energy to seem alive.
Aubrey stared, numb, assaulted by the complexity of the array. He guessed that the entire structure must have plenty of open space, but the overall effect was of overwhelming solidity, of the coalescence of uncountable elements into a massive, compound whole. It reminded him both of a lattice and something organic, something that had grown, branched and grown again.
And he could feel waves of magic rolling through the fantastic construction, waves that came from a single source.
'Where's the light coming from?' Caroline whispered.
Aubrey whispered back, not sure why he kept his voice low, but it seemed most appropriate in this unsettling place. 'In the middle. Where the magic is coming from.' He moved his head from side to side. Light flickered across his face, scattered by the jungle of pipes and wires.
'Must be big. And it's moving,' George said. 'Look around.'
On the walls and ceiling, shadows moved, sliding along, overlapping each other, slipping at speed, then being swallowed by others. 'The light is rotating,' Caroline said.
Aubrey crossed to the edge of the structure. He peered past a series of parallel cast-iron pipes, each only as thick as his thumb, but it was like looking into a thicket; he could see only three or four feet. He put his hand on a brass pipe, a modest one a handspan in diameter, and narrowed his eyes as he felt a tingle of magic moving through it. The pipe emerged from the wall near the stairwell and plunged directly into the structure at about chest height; but as soon as it entered, it bent at ninety degrees and shot upward.
Aubrey edged his head in underneath an earthenware pipe and a sticky bundle of wires as thick as his thigh. He tried to follow his brass pipe to see how high it went. He thought it bent again at right angles and ran parallel to the front edge of the cube for about ten yards. There it met a three-way junction and he lost it.
Aubrey's grip tightened. A few yards away, wrapped around a large cast-iron pipe, was a loose mat of copper wire, the same wire that had infested Maggie.
He shuddered, but forced himself to inspect the malignant wire more closely. The mat was thick, like weed, and it oozed magic. It dangled from the cast-iron pipe and linked it to a bright steel beam that was standing vertically amid a riot of other wires, pipes and struts, interlinked in a structure that hinted at organisation. He was tempted to try to find the underlying pattern, but it defeated him.
'Rails,' George said. Aubrey withdrew his head, catching his ear a stinging blow on a square wooden duct. He hardly noticed.
'What?'
'About twenty yards in that direction. A narrow gauge railway comes out of a tunnel and heads into that mess.'
'And we have a canal over here,' Caroline said, appearing from the shifting shadows. Motes of light flashed across her face. 'A tiny one, only a few feet across.'