It wasn’t impossible. There were lots of ways to make crystal structures out of the silicon anion, the fundamental silicon-oxygen tetrahedral building block.

But 86047 was just a rock, a fragment of some larger body that broke off an aeon or two ago. Why should it have this neat internal structure?

It was, he mused absently, as if something was living in there. Working, burrowing deeper into the rock, chewing up the olivine and leaving behind these deeper, complex layers…

“Mike, I want you to repeat these tests. Keep on with the other stuff, the more detailed work, but go over this again. Every couple of days. See if there’s any change.”

“Change?” Mike frowned. “In a piece of rock billions of years old? How can there be any change? What kind of change?”

“If I knew, I wouldn’t need you to run the tests.”

Mike made another note.

Very fine dust. Almost no cohesion or adhesion…

“What about the Arthur’s Seat samples?”

Mike had passed that work to another researcher. It took him a couple of minutes to retrieve the diffraction results from the intranet.

The diffraction pattern was unidentifiable. A silicate form nobody had seen before.

Nevertheless, to Henry, it looked familiar.

He had Mike call up the 86047 results again, and overlaid the two.

They were the same.

The diffraction results, of this sample of pulverized basalt from Edinburgh, and of the ancient Moon rock, were all but identical.

“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.