‘I know we are,’ Yuichi agreed. ‘Which is why we came out here.’

‘We’re here,’ said Nadia, pulling over by the side of the road.

I followed them back out of the truck, thinking again about the moon’s fracture and what it implied. Nadia left the engine running, and I guessed we weren’t going to be hanging around for long. From what I could see, we were in the middle of nowhere. There was no sign of anything resembling civilization, bar the cracked and broken tarmac of the highway.

A torch appeared in Yuichi’s hand, and he switched it on as he stepped towards a sign by the side of the road. He played the torch’s beam over the sign as the freezing wind bit at the exposed skin of my face. It read: ‘WELCOME TO THE WORLD-FAMOUS WINE-GROWING REGION OF NAPA VALLEY, CALIFORNIA’.

I stared at the sign, then up at the dark and lowering skies. Frozen devastation, in all directions.

‘In this particular alternate,’ said Nadia, ‘Yellowstone Park erupted, big time. Not everyone knows this, but beneath all those hot springs, geysers and attractive scenic routes lies a lake of molten magma the size of Long Island. And the pressure’s been building and building down there for millions of years, just waiting for the right conditions to come bursting out.’ She shook her head sadly. ‘From what Tony and other survivors tell us, they didn’t have much warning. There were a few more earthquakes than usual, as well as a sudden, inexplicable outwards migration of wildlife trying to get as far away from the park as they could run, swim or crawl.’ She raised her hands. ‘Then, boom. Enough ash and dirt got blown into the sky, in the space of a single day, to build a life-size replica of Mount Everest. It’ll be still more years before anyone sees the sun.’

‘And that all means that just about everything died,’ added Yuichi, switching the torch back off and stepping over. ‘Food cycle shattered, crops failing. Most species went extinct and the forests died. That, along with a catastrophic crash in global temperatures, pretty much did for civilization here.’

‘How many survivors?’ I asked, even as part of my mind refused to accept the evidence of my own eyes. I pictured them making the sign up and planting it in some remote region, in order to fool me into believing their ridiculous story. But to what possible end? And was such a notion really any less lunatic than what they were telling me?

‘After the plagues and the fighting, maybe a few thousand here and there. People like Tony were better equipped to survive, but they still suffered badly. It’s pretty much over for humanity in this place, and it’s the same on world after world after world.’

‘So there’s more than just this world, and the one we just came from?’