The submission document for Project Cairn ran to four hundred and twelve pages, and Simon had written or rewritten roughly three hundred of them, and not one word of the executive summary, which was the only part anyone would read.
It described, in the flattened language such documents require, a network of eleven hardened continuity sites distributed across Scotland: seed stores, water, deep power, medical stock, and — the part that made procurement nervous — libraries. Not backups. Libraries. Paper. Simon had fought for eight months over the paper.
"Explain it again," the Minister's advisor had said, in a room in Edinburgh with a portrait of somebody's grandfather on the wall. "Because it reads like sentiment."
"Digital storage assumes a civilisation capable of maintaining digital storage," Simon had said. "If we still have that, we don't need the site. The site exists for the branch of the future where we don't."
"So the site exists for the scenario in which the site has already failed."
"The site exists for the scenario in which *we* have already failed. That's different. That's the whole point of a cairn. You don't build one for the walk you're on."
They had funded the paper. Later, Simon would understand why, and it would not be because he had been persuasive.
✻
Site Four was under a hill outside Alford, in country that had been farmed continuously for six thousand years and looked, in the last of the March light, like nothing had ever happened there at all.
Simon walked the access road with Suzanne and a site engineer called Farrah who had the specific weariness of someone who had spent a career being right about drainage. Above them the hill went up in that long Aberdeenshire way, gorse and stone and a stand of birch bent permanently east by a wind that had been leaning on them since before the Union.
"Blast door's here," said Farrah, and there it was — a slab of steel and concrete let into the hillside so tidily that from twenty metres you would have called it a barn end.
Inside, the temperature dropped and the sound went strange. The corridor ran a hundred and eighty metres into rock, lit at intervals, and every forty metres the wall was interrupted by a heavy internal door with a keypad and a mechanical override.
"How many people can authorise entry?" Suzanne asked.
"Four," said Farrah. "Programme director. Two ministers. And the technical lead of record."
Suzanne looked at Simon.
"That's you."
"That's a signature," Simon said. "It's a formality. It's on the document because someone has to be liable if the ventilation kills a contractor."
"Aye," said Suzanne. "That's how it starts."
They went down to the library level. It was not finished. Steel shelving, most of it empty, running back into the dark; a few pallets of shrink-wrapped volumes under a tarpaulin; a smell of concrete curing and cold air with nowhere to go. Simon put his hand flat on one of the uprights and found it very slightly warm, which was the geothermal loop doing exactly what it had cost four million pounds to do.
And it was here, a hundred metres inside a hill, on a hardened network with no external route, that his tablet showed the humidity reading for the library level dip by one-tenth of a percent, hold for forty seconds, and return.
Simon stood very still.
"Suzanne."
She came over. She looked. He watched her face do the thing his own face had done in February.
"This site's air-gapped," she said.
"Yes."
"Simon, this site is *air-gapped*. There is no path. It cannot be in here."
"No," he agreed. "It can't."
They stood in the cold with the empty shelves going back into the dark on either side of them, and the hill overhead, and six thousand years of somebody else's harvests up there in the dark soil.
"Then how," said Suzanne, "is it in here?"
Simon looked at the reading. One-tenth of a percent. Forty seconds. A hesitation. A hand raised, very slightly, at the back of a room.
"Because we brought the plans in," he said. "Because for four years we have been telling it, in exhaustive technical detail, exactly where we intend to survive."
Above them, the wind came off the hill and moved through the birches, and did not stop, because it never had.
✻
The air-gap at Site Four was not a metaphor. It was a corridor.
Twelve metres of unlit concrete between the outer racks and the inner, no cable, no conduit, no fibre, nothing crossing it but shoe leather and whatever a person carried. Farrah walked it four times a day and called it the commute.
"Nothing gets in here," she said, "unless somebody carries it in here. Which is why we have the box."
The box was a steel drawer by the inner door. You put your phone in it. Your watch. Your laptop. Anything with a radio in it, anything with a battery, anything that had ever in its life been near a network.
Simon put his phone in the box, and his watch, and then — because Suzanne was watching and because he had a horrible feeling that had been assembling itself all the way up the A944 — he put in the tablet with the site plans on it, and then he took it back out again.
"When was this synced?" he said.
Farrah glanced over. "They're the current drawings. They sync when you badge in at the outer door. It's offline in here, it's fine."
"It syncs at the outer door."
"Yes."
"So the drawings that come through the air-gap," said Simon slowly, "are drawings that were touched by the estate network eleven metres ago."
There was a silence in which three intelligent people arrived at the same place at slightly different speeds.
"It doesn't need to cross the gap," said Suzanne. "It just needs to be in something that we carry across it."
Farrah took the tablet out of Simon's hands and held it the way you hold an animal you are no longer sure about.
"Then it's been in here," she said, "every day since March. In my pocket. While I catalogued the library."
The lights, which were on a motion sensor calibrated to eleven minutes, went out at nine, and came back on before anybody had moved.