His room turned out to be a box, a typical city centre room, no doubt ruinously expensive, but His Majesty’s Government could worry about that. His escort, a couple of bullshitting squaddies, were booked in the hotel, down the corridor.

He threw his holdall down on the bed, shucked off his filthy clothes, and climbed straight into the shower, which was a modern fitting with a hot and powerful jet.

Ash-grey shit soaked out of his skin, and made little whirlpools at the plug at his feet. Bits of burned Edinburgh, rock just a day old, the youngest rock on the planet.

Drying off, he turned on the TV. All the regular programmes were suspended, save for one channel that was carrying children’s TV — he saw five seconds of it, weird little aliens that bounced around and spoke gibberish, Christ, bring back Sesame Street — and on all the other stations there was, of course, only one story.

Images of Arthur’s Seat, before and after the explosion. Before: waving cultists in their purple pyjamas, upturned faces like daisies, maybe one of them Michael Dundas’s.

And Arthur’s Seat after, a smouldering crater, still pumping out ash and steam.

And all of the people, as volcanologists say, part of the sunset now.

Here was the New Town after the pyroclastic flow, like an image of Hiroshima after the bombing: stumps of buildings, shorn off at little more than knee-level, surrounded by smashed and strewn rubble and covered by a ghostly powder-grey layer of ash, nothing left of the great Georgian design except the rectangular layout of the streets.

There were people already picking through the rubble, some in volcanologists” protective suits, others, heroic, in nothing more than regular emergency gear. The scientists were recording what they could, pyrometers and thermocouples measuring the dwindling heat of the smashed ground. The rescue workers were using microphones and other gear to search, forlornly, for survivors, maybe people who had ridden out the ash storm in cellars. So far, the news guys said, not a one had been found.

Henry could see how the heavy ash cloud, seeking the lowest points to pool like the sluggish liquid it was, had swept like a transient river around the other bony basalt outcrops, Calton Hill and the Castle; in fact most of the structures on those hilltops were still standing. But both plugs were marked, distinctly, by the cancerous grey scars of Moonseed pools. It would only be a matter of time before they went the way of the Seat, and added to the destruction of the area.

And all the time the Moonseed was spreading, chewing up the Earth, disrupted briefly by the destruction it caused, but always returning, stronger and more widespread than ever.