'Not now, I think,' Caroline said. 'We have a mission ahead.'
Aubrey was torn, but he reminded himself that Maggie and her Crew were still missing – and Dr Tremaine was still out there. This could wait. 'Of course.'
'I'll keep it safe,' George said and he wrapped it in his handkerchief before slipping it into his pocket. 'There. Safe as the Bank of Albion. Or safer, really.'
They hurried from the tomb and quickly worked their way through the marble vault. After a scramble out of the Roman ruins, where Aubrey delightfully had to assist Caroline, they were back in the main tunnel. Once there, Aubrey leaned against the wall for a moment while George and Caroline argued about the way ahead. With glum certainty, he realised that his magical expenditure had already come at a cost. He ached, and shivering threatened to seize hold of him.
As he tried to steady himself, he realised that, for the present, this was his lot. He couldn't stop using magic. It was like deciding not to use one of his arms – awkward, difficult and potentially dangerous.
Live with it, he thought, and live long enough to find a way to sort things out.
He controlled his shivering through an act of will and straightened to join his friends.
The main tunnel trended upwards for a few minutes, then it opened out into a larger tunneclass="underline" a wide, open drive. It was long, and wide as a boulevard, with some bracing timbers as well as the magically stabilised earth. Along one side of the excavated area Aubrey could make out the foundations of buildings, the first reminder he'd had of the world overhead for some time.
Sitting in the middle of the underground boulevard, twenty or thirty yards ahead, was an elaborate machine.
George and Caroline stared. 'I think we've found our tunneller,' Aubrey murmured.
The machine was the size of an omnibus, completely enclosed in smooth steel apart from a window at the front. A large auger projected from the front, twice the height of a man, and it was surrounded by immense electric lights in wire cages. Large metal plates ran around all four wheels and Aubrey was startled to see that these plates were connected, like links in a chain. He squatted, taking the lantern from Caroline as she peered at the welding, and inspected the undercarriage of the contraption, growing increasingly excited at what he was finding.
By the lantern light, he saw that the cabin had a single seat. No room for passengers; this was a solo craft. Levers, knobs, switches were arranged within reaching distance. All were mysterious, unlabelled except for one brass handle – 'Ignition'. Automatically, Aubrey tugged on it but was not surprised when he found it locked – magically locked, to judge from the tingling in his fingertips.
A set of three large brass rings – each as tall as George – jutted from the rear of the machine, one behind the other. Hundreds of silver rods ran around the perimeter of each ring and linked them together so that they were a handspan apart. When Aubrey touched the rings, he felt the magical residue and immediately knew what they were for.
'They belch out the stabilising sheaths.' He stood and wiped his hands on his filthy trousers. 'The auger digs, the machine pushes aside the earth, and the rings shoot out stabilising magic that locks the earth into place.' He shook his head with admiration. 'It's a masterpiece.'
'A Dr Tremaine construction?' Caroline said without a trace of admiration.
'I'd say so. Dr Tremaine is a man for elegant machines.'
'So where is he?' Caroline demanded. 'If this is his machine, shouldn't he be nearby?'
The thought gave Aubrey a momentary alarm. Then he placed his palm against the cowling of the tunneller. 'It's cold. Hasn't been used for some time. Dr Tremaine could be anywhere.'
Aubrey walked along the length of the tunneller, then around to the far side. He lifted the lantern and faced the mighty foundations of a building.
Thrusting down from the overburden were large stone blocks, reinforced with steel bars driven through each and bolted, linking them together. They rested on solid bedrock. Aubrey looked up. The weight resting on these foundations meant that they were immoveable, part of the rock itself, as if they'd grown there. 'He's excavated right along the foundations of our Bank of Albion. I'd say the Vault Room is through here.'
George broke off from studying the tunneller's gearing and joined Aubrey's inspection of the foundations. 'How thick are they?'
Aubrey cast his mind back to his day in the vault with his father. 'Ten, twenty feet? There's no getting through that lot.'
'Then how is Dr Tremaine imagining he'll waltz in?' Caroline said.
Aubrey looked along the length of the foundations. 'Does the tunnel continue past the bank?'
'It does. And that doesn't answer my question.'
'No, but it's a step toward answering it.'
Aubrey was sure he was close, that answers were dancing just a few inches beyond his fingertips. He was tired, aching, filthy and suffering from the disunity of his body and soul – but he was buoyed by an urgency that came from his desire to succeed whatever the circumstances.
He walked along the length of the foundations. It wasn't long before he was on the edge of Caroline's lantern light and entering the realm of shadows. He tripped on a sheaf of tarred wires that emerged from the earth and vanished into the darkness ahead, but he barely noticed them.
Another tunnel, at right angles to the main shaft, had been bored along the side of the bank's foundations.
The tunnel mouth became clearer, shadows fleeing. 'Someone wants to see as much of the bank as he can,' Caroline said. She held the lantern up, and Aubrey could see the calculation in her eyes. 'Was he trying to find a weak spot?'
'In the bank?' George said, joining them. 'No-one's managed to break into the Bank of Albion. Ever.'
'Dr Tremaine is a man for firsts,' Aubrey said. He scuffed at the earth of this side tunnel. It wasn't as compacted as the main tunnel. Was it more recent?
His scuffing uncovered something that clinked when he nudged it with his foot. With astonishment, he realised that it was a chain.
He gouged at the earth with his heel and discovered that the chain seemed to run underneath the tunnel floor, extending into the distance.
'What is it?' George asked.
'An enigma.'
'One of those spiny anteater things from Antipodea? How did it get here?'
Aubrey lifted his head only to see George grinning at him.
'Now,' George said, 'for a second, you actually thought I'd confused enigma and echidna, didn't you?'
'Touché, George. Now that you've kept me on my toes, I'll ask you – what's that behind you?'
'I feel like I'm in a pantomime,' George said. He turned, but slowly, ready to disengage himself from any upcoming joke.
Twenty or thirty yards away at the edge of the lantern's light, was a shadowy bulge, an irregularity in the straight, sheer stone of the foundations.