She gave his shoulder another shake; that, he realized was the mysterious force that was moving his arm. So he wasn’t having a fit, then. He groaned, opening his eyes wide.

‘Mac!’ she shouted, overjoyed. ‘You’re alive!’ With that, she launched herself at his neck. His head thudded back into the ground, and everything turned red as a fresh wave of pain took over.

When the room finally got off the merry-go-round, he pushed himself up to a sitting position, Theo still draped over him. He looked around, trying to take stock of his surroundings.

He was in another cavern—no, not a cavern, a tunnel so wide that three men could have walked abreast in it, although admittedly it would have been a tight fit. It ran forward about a dozen feet and presumably further, but what lay ahead didn’t matter, because the rest of the tunnel was blocked, sealed off by the tons of rock and debris jammed between the floor and the ceiling. The tunnel itself was very different from the pipes they had been running through. It was almost certainly natural, completely made of rock, with craggy spurs and large mineral formations twisting out at odd angles from the ceiling and walls. Overhead, the ceiling had a row of lanterns hanging from it, creating a corridor of light all the way down the centre of the tunnel. The rest was bathed in a constant, shadowy darkness.

He could see the others, too. Theo, attached to his chest, in front of him. Colby and his men standing next to the wall of rock, talking animatedly about something, but in such low voices that he couldn’t make out what they were saying. On his right sat June, with a grim expression on her face and a faraway look in her eyes.

‘Wha—what happened?’ he asked.

Silently, she shook her head.

‘The blast … there was a blast. What happened after?’

‘You got hit by a rock. The cavern came down. We only just made it. But the shock brought this one down too.’

A bolt of panic shot through him and he sat straight up, then wished he hadn’t, as his head spun. ‘One moment, Theo,’ he said, gently disentangling her from around his neck. It hurt just to smile.

He stood up, swaying a little, and immediately learnt three things—one, that it was a bad idea to attempt to stand while still groggy; two, that hitting the ground with your head was not one of those things you grew accustomed to over time; and three, since on this occasion he retained his consciousness, that it hurt like hell. A second later, he added a fourth: given the right circumstances, it was perfectly possible to see stars in the daytime.