The climb, he knew from a lifetime’s experience, looked a lot stiffer than it was. The grassy ground was dark, still in the shadow of the turning Earth, even though the sky was already bright; and the dew made it a little slippery underfoot. The path was heavily eroded — too many visitors — but the climb was one Mike had been completing since he was a kid, and it didn’t take long to reach the broad, flat summit.

He stood on the red-brown, lumpy rock here. The rock was agglomerate, the exposed neck of the old volcano. There were two summit monuments up here, sparse concrete blocks.

He was alone. The Seat attracted few tourists, compared to the Castle Rock anyhow; mostly you saw locals, dog-walkers.

He turned slowly around. From here you got a panoramic view of the city and its environs, nestling around the volcano plugs; Arthur’s Seat was the highest hill in Edinburgh.

He could see the Pentland Hills to the south, the central lowland plain stretching off to the west, and the river to the north, the city splashed along its southern coast. He could make out the docks and the twin stacks of the Port Seton power station; the water beyond looked so flat and still it might have been moulded from steel. And there was the rocky northern coast of the Forth; on a good day you could see the peaks of the Highland massif, all of seventy or eighty miles away.

Venus was setting, but it was still bright enough to cast a reflection from the small waves on the Forth.

The air, blowing off the Forth, was fresh and laced with salt; he breathed it deeply, swinging his arms, invigorated, exhilarated.

All this out of his back door, and a Moon rock waiting for him back at the lab. Already he had more than a good feeling about how his relationship with this Henry Meacher was going to pan out. God, he thought, I love this job.

But first, he had to see his sister. He patted his pocket, to make sure the little vial of dust he had secreted there was safe.

Then he made his way down Arthur’s Seat, by a different crack.

He descended towards a sandstone ruin called St Anthony’s Chapel.

This was a grey heap of rubble not far below the summit of the Seat, in the lee of an exposed crag; time had left one wall intact, with a door and window gaping into nothing. The chapel was thought to date from the fifteenth century, but nobody actually knew; Edinburgh’s history had been chaotic.

As he headed towards the Chapel, through a steep-walled old glacial cwm called the Dry Dam, Mike could hear a single voice — a man’s — floating into the morning air.