“Now,” Henry said, “what the hell do we have here? What is the connection between this bartered old piece of the Moon, and an innocent Edinburgh landscape?”

But Mike turned away, oddly reluctant to respond.

Mysteries on mysteries, Henry thought, puzzled by Mike’s reaction.

When he went up to the Seat, he found Blue and Jane waiting for him.

“I see you found each other.”

Blue was grinning so wide his teeth were twinkling. “I see you found each other,” he said.

“Knock it off.”

Jane said, “I was over with the cultists—”

Blue giggled. “She saw me sniffing the rocks.”

“So I knew he had to be something to do with you.”

“I’m glad you two are getting along,” Henry said drily.

“I’ve been telling her all about your past,” said Blue.

“Oh, shit.”

“Yeah,” Jane said. “Blue tells me his hotel is okay, but they are — what did you say?”

“Skinning me like a country chicken.” Blue cackled.

She said drily, “So which part of Arkansas are you from?”

“Come on, Blue,” Henry said. “We’re here to work.”

Blue nodded. “We need to get closer. The young lady—” he nodded at Constable Decker “—will allow us through the tape.”

“She will?”

“I vouched for you,” said Blue.

They lifted the tape and ducked underneath it. Cautiously, they approached the edge of the summit dust pool — which, once more, had spread since Henry last looked. It sprawled, ragged, over the lumpy rock.

Blue threw lumps of turf into the pool — they disappeared immediately, without so much as a ripple — and he kneeled down, a little stiffly, to sniff the air.

Blue said, “It might be liquefaction.”

Jane said, “What’s liquefaction, exactly?”

Henry said, “Where earth tremors shake up certain kinds of soils. Seismic shear waves passing through a saturated granular soil layer distort its structure, and that causes some of the void spaces to collapse—”

“In English.”

“For a while, the soil acts like a liquid.”

“But,” Blue said, “liquefaction is only found when the sands and silts were deposited recently.”

Jane said, “Recently?”

Henry shrugged. “Say, less than ten thousand years ago.”

“Even then,” Blue said, “you need ground water within thirty yards of the surface… This is an ancient volcanic plug. I can’t believe this is liquefaction, as we understand it.”

“Then what?”

He spread his frail hands. “I’ve never seen anything like it.”

“Congratulate me,” said Henry. “A new geological breakthrough.”

Blue drawled, “Even a blind pig finds an acorn sometimes.”

But the banter was, Henry thought, on auto-pilot. Blue seemed to share some of his own sense of dread, as he stood here and studied this unclassifiable phenomenon.

“So,” Jane said, “what are you going to do now?”

“I think we should bring the portable lab out here,” Blue said.

“What portable lab?”

Henry said, “He means the VDAP’s. That’s the Volcanic Disaster Assistance Program. A kind of volcano SWAT team run by the US Geological Survey. They have a portable lab for studying geological disturbances which—”

“Oh, sure,” she said. “Why don’t you get your ex-wife to beam it down from the Space Shuttle?”

“Jane—”

“This isn’t the Third World, you know. Even if it was, you would still be a patronizing arsehole American.”

Henry eyed Blue. “Of course she’s right. Everything we need should be here.”

“Okay,” Blue said. “So we wire the mountain. We need seismometers. A network of them, at the rim, on high-gain rock sites. They will have to be moved regularly as the pool progresses, I suppose… We’ll need volunteers for that. The seismos will be linked by radio telemetry to a central point.”

“We’ll use my lab,” Henry said. “We’ll need a war room.”

“Why a network of seismometers?” Jane asked. “Why not just one or two?”

“Because we have to triangulate,” Blue said with gracious patience. “We must locate the movements of the ground in three dimensions.”

Henry said, “What else?”

“We should do some real-time and spectral seismic analysis, to understand the growth of this phenomenon.”

“Deformation monitors?” To Jane he explained, “When magma builds up beneath a volcano the ground distorts.”

“Yes,” Blue said. “Whatever you can find. Ideally laser based EDMs—”

“Electronic distance meters,” Henry told Jane.

“And GPS receivers.”

“Global—”

“Positioning System?” she said with some satisfaction.

“A cospec for gas emissions,” Blue said.

“Yeah.”

“Henry, I’d really like BOB here.”

Jane said, “Who’s BOB?”

Henry smiled. “A VDAP computer program. For rapid analysis of time-series data in crisis situations. Okay. And I’d like to order up regular aerial surveys to map the changing extent of the thing. My shoe-leather metrics really aren’t good enough. Later we should think about acoustic flow monitors if there are lahars, microbarographs—”

Jane said, “That sounds like it detects changes in atmospheric pressure.”

“So it does.”

“Why that?”

“Because it’s a good predictor of a volcanic explosion.”

“…Oh.” She was looking at the pool rim. “Look at this,” she said. She pointed to a patch at the rim of the pool, where bare rock showed through the grass.

A foot-wide patch of rock was — Henry thought, shielding his eyes against the sunlight — glowing.

The rock flashed. Henry jumped back. He’d felt heat on his face.

When he looked again, the rock was changed. It had turned to the fine silvery dust, characteristic of the rest of the pool.

“Holy shit,” Henry said. “Did you see that?”

Blue said, “At least we know how it spreads now.”

Jane looked from one to the other. “I can’t quite read you two,” she said. “You are interested in all this. Fascinated, even. But, underneath that… You’re afraid, aren’t you?”

Henry and Blue exchanged a glance.

“Why?” said Jane. “Do you think this is a volcanic event? Arthur’s Seat has been dormant for a third of a billion years. Do you think it’s becoming active now?”

“We don’t know. This isn’t like any volcanic event we’ve faced before.”

“Then what is it?”

“We don’t know that either.”

She nodded. “And that’s what’s frightening you.”

“Yes,” Blue said. That is what is frightening us.”

“The growth rate has been maintained for weeks,” Henry said. “The pool is still pretty small now, but it’s not going to stay that way.” He regarded Jane. “We have to be ready to face that.”

“I understand.”

Blue was studying the air. “It is blowing away.”

“What?”

“The dust. Spreading in the breeze.”

Jane asked, “Is that important?”

“I don’t know.”

Blue was glaring at the dust, his face a sour mask.

“So,” Henry said. “What do you think, old friend?”

Blue sniffed. “This is something which should not be here It is like a cancer, on the face of a good friend.”

Yes, Henry thought. That was exactly it.

Something new. And unwelcome.

Bad news.

They made their slow way down the Seat.