“Yes.”

“Like that. We’re going to be walking over a meringue, a thin crust of rock. Take a wrong step, and poof.” He snapped shut his fingers. That’s why there’s no heavy equipment here. We’ll follow these routes.” He indicated the highlighted trails. Other areas, Ted saw, had been sectioned off by hand-drawn blue hatching. Moonseed outbreaks.

“So how do we know where is safe?”

Blue shrugged. “We can’t be sure. We do aerial surveys, every day. Debriefs from the soldiers and police and fire boys who work in here.” He eyed Ted. “We spend human lives, the lives of civilians or scientists or emergency workers doing their duty. That’s what this thing is. A map bought with human lives.” Blue faced him, his face a broad round mask behind his scuffed and dirty faceplate. “Now, you listen to me, old man,” he said.

“I’m not much older than you.”

“Bullshit. I’m taking you in as a favour to Henry, who likes you because he’s porking your daughter.”

“I wish you’d say what you think,” Ted said drily.

“Only fools like me should risk going into such places. And for sure a dinged-up old fucker like you is just a liability.”

Blue’s mix of Japanese accent and cowboy phrasing was, Ted thought not for the first time, bizarre.

Blue leaned forward. “Now, I don’t give a rip what Henry says. Henry isn’t here. If you start coughing and spluttering and wheezing and doing other old-man stuff, you’re straight out of here. I want that clear right from the git-go. You got that?”

“I got it.”

“Okay. Then let’s get it over.”

Blue folded his map, and they walked on.

Ted wanted to get as close to the Seat as possible. That was, he reasoned, where he would find what he sought. But Blue skirted west, heading towards the New Town, and he had to follow.

In the rubble of the west of the city, there were more people than he had expected.

Many of them were civilians, poking through the ruins of their homes, business suits and summer skirts stained with ash. Some of them were filthy, their faces grimed by layers of mire; they looked as if they hadn’t washed or been properly fed for days. Evidently not everyone had made it to the comfort of a Rest Centre.

But there were provisions for people, even here. They passed a Red Cross tent complex, beds and a simple field hospital, and what looked like a morgue. Human life and activity, slowly intruding, here on the surface of the Moon.

A squad of soldiers went by. They wore grimy fatigues, cloths bound over their mouths. They looked exhausted, but they were carrying spades and body bags, on their way to another clean-up. None of them spoke. They looked inordinately young to Ted: probably younger than both his children, not much older, in the greater scheme of things, than poor Jack.

The Army crews had been working here since the volcanism had died away. But there were still many bodies. Ted could see that, just walking here.

Some of them lay where they had been trapped in the rubble of their shattered houses, their limbs splayed, under roofing timbers or steel joists. The corpses were already bloated and discoloured, faces swollen to a youthful smoothness, freed of the contortions of pain, the bloody reality masked by the thin painting of ash. In Newington there seemed to have been a more major fire — the buildings were uniformly razed — and in the main road that threaded through the suburb, they came across many bodies, apparently unburned, men, women and children alike, lying scattered across the road surface. He saw a mother with a baby. The mother had been trying to hold her baby up, away from the road surface. And in that posture they had been petrified.

Evidently there had been some kind of miniature fire storm here. The road tarmac had melted. The people, fleeing the fires, had gotten stuck, like insects on fly paper, and, suffocating, had fallen. Now their corpses were glued in place, cemented to the road surface which had betrayed them.

How must it have been? Ted wondered, staring at the corpses. Not the fact of death itself, but those few seconds, knowing its inevitability: knowing that today was the day, now was the hour, death bursting out of the mundane background of these quiet suburbs; and suddenly there was nothing you could do to protect those you loved, not even the most innocent. How must it have been?

Edinburgh had become a city of tableaux, he thought, of tiny fragments of immense and undeserved suffering, such as this.

Ted and Blue inched around the bodies, trying not to get too close. Flies swarmed, and the stench was powerful enough to penetrate Ted’s protective suit.

They walked on into the heart of the city. The heat of the June day climbed.

At St Leonard’s, Blue cut right, and headed through the few blocks of housing directly towards Arthur’s Seat. Ted followed gingerly.

The damage was so extensive here it was impossible to make out even the outlines of the streets. Everything had been smashed and burned and shattered by the ash flow, so that rubble lay everywhere in heaps that looked, from a distance, almost smooth. Easily negotiable. But close to, much of it was actually hot to the touch and unstable, eager to collapse to a more consolidated profile.

Ted found the going much more difficult, with jagged edges of wall eager to trip him, or rip his suit, or send a miniature landslide down on top of a foot or leg. In some places the rubble was smoothed over by layers of pumice and ash, making it still more treacherous, and even Blue was forced to slow right down, and move forward with much more caution.

From the air they must have looked like two silvery bugs, inching their way across the shattered, transformed landscape.

That wasn’t the worst of it, though. Here, Ted could tell he was close to the Moonseed.

The air was so still. And there was a tinge, a silvery glow, as if the sunlight was being scattered by a smog of iron filings.

At last, the world was reduced to its essentials. Moonscape below, silver-stained sky above, himself and Blue and this rubbly plain, his own breathing, the steady thump of his old heart, the tug of pain at his wounded chest. And as his faceplate grew opaque with the mist of his breath, the fine layer of ash dust he had to keep wiping away, his universe narrowed further, became simpler still.

It was almost peaceful.

He wondered what he would smell, if he raised his hood.

He thought about the Moonseed, and meringues, and the unknown pit of alien forms somewhere beneath his feet. It was as if the Moonseed had turned this place into an alien landscape, not Earth any more.

Blue mounted a thick slab of wall, breathing hard, and looked back at Ted. “You are doing well.”

“Thanks.”

“For a geologist this is not so strange, this landscape.”

“What?”

Blue waved a gloved hand. “No life. Nothing but minerals. The world reduced to its essence, by the burning power of the alien among us. Come, my friend. Not much further.” And he stepped forward and continued his progress.

After a time, the housing remains ran out. They had reached the western edge of Holyrood Park, the old garden which had contained the Seat, overlooked here by the Salisbury Crags.

The Crags had gone. The Moonseed pool had come spilling out from the Crags in great silvery tongues. But the turf survived, in narrow bridges pushing a few yards more into the Moonseed, evidently fragile. Ted could see the burned and fallen trunks of trees, grey and lifeless on the scorched, ash-strewn turf.

Further to the east, towards the heart of the Seat, there was only the silver-grey glow of Moonseed light, all the geology and structure there — a billion years of Earth history — reduced to alien smoothness.

“Come on,” Blue whispered. “We can go a little further.”