‘Some kind of alert,’ said Nadia, her voice clipped. ‘I just hope it’s nothing to do with that tremor a minute ago.’

As it would soon turn out, it had everything to do with the tremor. As if in response, the ground shifted once again beneath our feet, just very slightly, and I automatically stepped back from the edge of the chasm.

I looked over at Nadia; her face was barely visible behind the visor of her spacesuit. My suit’s electronics painted her face in witchy green. ‘So what’s it about?’ I asked.

‘Don’t know,’ she replied. ‘The suit radio’s a piece of crap. Hasn’t got enough range even to contact our Forward Base directly.’ She gestured towards the Excursion Vehicle parked nearby that had brought us here. ‘Let’s head back inside.’

I nodded, and followed her back over to the vehicle, sweating and cursing as I tried to walk in the heavy suit. I felt fitter and in better shape than I had in a long time, thanks to the intensive programme of training the Authority were putting me through. They needed their Pathfinders fit and healthy, but trying to walk around in the suit felt as if I was trying to wade through rapidly hardening mud.

The Excursion Vehicle – or EV for short – consisted of a pressurized steel cylinder with wheels like rugged balloons and a slit-like windscreen at the front. Once we had cycled through its airlock, Nadia barely paused to pull her helmet off before climbing into the driver’s seat and leaning over a microphone built into the dashboard. I stood listening, my own helmet under the crook of one arm, as she spoke rapidly.

‘Nadia Mirkowsky here, out on EV-6. I just received a priority alert and felt a couple of strong tremors. Can you give me any more information?’

She repeated this message twice more before a reply came. ‘Miss Mirkowsky?’ said a voice. ‘There’s a general evacuation alert being broadcast and your orders are to get back immediately.’

‘Evacuation?’ I echoed, more than a little alarmed, but Nadia abruptly put a hand up to quiet me.

‘Anything else?’ she asked. ‘Last I heard, there was a dig team down inside the Retreat.’

The Retreat was the name the Icelanders had given to the subterranean stronghold in which they had hoped to survive the death of their world. ‘I can’t tell you their status,’ came the reply, ‘but the evacuation order still stands. All I know is, the seismometers are going off the scale, and anyone who’s on excursion needs to get back here now. It looks like Hekla’s going to blow sooner than expected.’

‘Wait a minute,’ she said. ‘Why can’t you tell me the status of the dig team?’