He didn't look dangerous. On the small screen he looked comical, waving his arms, his rant a squawk from the phone's speakers.

'The People's Republic of China,' he was saying, random syllables underscored with a pistol finger, 'has taken over the world without firing a shot. This is not even controversial! And yet, in all our-'

Gabrielle switched him off, then shifted her chair so that she could face me.

'Don't you realise? He's one of our MSPs. We're both in his constituency. And I saw him when he was campaigning. He knocked on our door.'

'He knocks on doors?' I said, impressed.

'Oh yes,' said Gabrielle. 'None of that lazy do it all online stuff for him. He actually said to me, you haven't campaigned properly in an election if you still have the same shoes at the end as you had at the start. Renewal's new, so they have to do things the old way.'

'What was he like?'

'Well, he only had a few minutes, and he started off all affable, talking about freedom and enterprise and so on, sticking up for small businesses and young families, all that. And then ...' She frowned, as if trying to remember. 'Hard to put a finger on. Something dodgy in the body language. Emphasis on local people, young mums, hard-working families ...'

I laughed. 'Motherhood and apple pie?'

'Apple pie?' She didn't seem to get the allusion. 'No, but he did talk about corner groceries, and there was a bit about motherhood, all right, and everything he said was sort of subtly old-fashioned. Like he was appealing to people who've never really got used to immigrants and refugees and working mothers.'

'You mean, the very old?'

Gabrielle shrugged. 'Don't underestimate that as a share of the vote. Anyway a I didn't like him.'

'Fair enough,' I said. I leaned forward to depress the cafetiere plunger and I considered telling her what I knew about Baxter, and decided not to.

Later, as we walked across the Links to the Meadows in the continuing rain, I held her copper-coloured girly umbrella over us both, and she put her arm around my waist to stay close and underneath.

And that was us, us.

PART FOUR.

17.

Gabrielle, tiny beside the standing stone, tinier yet on my phone screen, waved and pointed to something above and behind me.

'Look!' she called out. 'A flying saucer!'

I snapped the pic and turned to the vast Orcadian sky. Low over the low hills came, not a saucer but a bright globe, silent as a balloon, swift as a small aeroplane and about the same apparent size. I gazed at it stupefied for a moment, then tracked it with the camera as it passed over our heads, a couple of hundred metres up, and on out over the sea where it vanished in the glare and glimmer. Gabrielle was doing the same a by the time I'd hurried over to where she stood, she had the UFO identified.

'It's a test flight,' she said, looking up from her phone. 'Says here it's piloted.'

'Wow,' I said. 'British Avionic Systems, by any chance?'

'That's the one,' she said. 'How did you know?'

I grinned and put an arm around her. 'You talked about it the first day we met up.'

'Did I?' she said. 'I'm impressed you remembered.'

'We were going to have a look at their stall,' I said. 'Actually, I don't remember if we did or not.'

I thought back to that day. It had been wet, hadn't it? Yes: Gabrielle sticking close to me under the brolly. The Meadows muddy, some clown on stilts getting stuck, debates under canvas marquees and geodesic tepees, the smell of grilling patties and deep-fried doughnuts, face-painted kids, balloons, buzzing camcopter swarms, huge crowds, arguments, the warm, muggy, sticky all-embracing hug of a popular front in formation. I remembered looking on a phone screen at Jim Baxter's strange rant, but not a visit to the stall of the company he'd worked for before he went into politics.

'Probably not,' I concluded.

'Looks like we missed out, then.' She replayed the video capture, froze and zoomed. 'Look at that, just a silver ball. Heck, look closer.' She worked her thumb, until I could see in the globe's mirror sheen the distorted reflection of her face looking up, and the upraised phone. For a laugh, she zoomed to the highest magnification, to show the reflection of the phone's camera lens and within that a bright pixel or two: the reflection in the lens of the globe itself.

'I mean, how does that work?' she said.

'Reflection of reflection of reflection?'

'No, I mean it looks like a solid polished steel ball, but it can't be. The air's passing right through it, isn't that the idea?'

'Metamaterial,' I said, with a handwave.

'Like that explains anything.'

'I've written about it,' I said. 'Well, them. There's lots.'

'Yeah, yeah. I can't read everything you write.'

'Really? I'm hurt.'

'Come on,' said Gabrielle. 'I don't think you read everything you write.'

'Now I'm really hurt.'

'Time I took a picture of you, then.' She waved an arm. 'Which stone do you want to pose beside?'

I looked around the wide, incomplete stone circle, sizing up backgrounds of hills, the next field, sea and sky.

'Over there. Maybe take it from ...'

I pointed.

'OK.'

We strolled off in divergent directions. As I walked up to a slab that seemed to get taller and paradoxically thinner as I approached, I considered whether I should mention my long-ago close encounter to Gabrielle. If I did, she'd be hurt a really, not in banter a that I hadn't told her before. Bewildered, even. I'd had long enough a just over three years, to be exact. She'd wonder what else I hadn't told her. She might ask Calum, and he might brag to her of how he'd fooled me into thinking that he (and by implication, she) was part of a secret race. Calum was a pal, my oldest and closest friend, still was even if we didn't see much of each other, and it was exactly the sort of thing I wouldn't put past him a precisely because he was a pal. He was loyal, but he'd see this as a laugh. Perhaps I should, too.

I laid my hand against the rough stone, and turned.

'Smile!' Gabrielle shouted.

I couldn't not.

'Right a bit, I'll get both stones.'

I moved. She waved. 'Got it.'

I grinned and waved back, then turned to press my hands and forehead against the stone, a tall, neatly split sedimentary slab, probably hacked and hauled from a nearby shore in some feat of skill and cooperation that made me wonder, and made me proud. Beyond that, unimaginably far beyond that, the rock itself, cemented by silent relentless pressure on the floor of a vanished sea from eroded particles of mountains more ancient yet.

'What were you doing there?' Gabrielle asked when I rejoined her. 'Praying to the old gods?'

'Just thinking,' I said. 'About the folk who raised it. Our people. We've been in this land ten thousand years.'

'Yeah,' said Gabrielle. 'Since the ice left.'

I glanced sidelong at her, and smiled, and didn't say that some of us might have been here for longer.

We headed back to the hired car, piled in and drove up to the Ring of Brodgar, then to Skara Brae of the grassy mounds around stone beds and shelves and kitchen sinks and on to the Broch of Gurness. By the time we'd circled Gurness's green ramparts and explored its stone labyrinth it was late afternoon. We bought paper tubs of ice cream in the visitor centre and dawdled back to the car park.

'Tomorrow, Birsay and Maes Howe,' said Gabrielle, licking sticky fingers and looking at the unstamped sites on our visitor pass.

'Yeah,' I said. 'Today we get stunned by the Stone Age, then impressed by the Iron Age, then tomorrow get gobsmacked by the Stone Age all over again.'

'It's like that, isn't it?' she said. 'Going from Skara Brae to here. You can see at Skara Brae what Gordon Childe saw, where he got this idea of our communist ancestors in their cosy hobbit-holes and then seeing here at Gurness the origin of classes with the walls and the wealth and all the work that must have gone into it.'

'In real life we'd have smelled our supposed communist ancestors,' I said. 'From here, probably.'

'Well, their midden heaps, anyway,' said Gabrielle. She wrinkled her nose. 'I couldn't stop thinking about what those mounds of shells and bones must have been like to live among.'

She was in the driving seat. I glanced at her profile as she turned the ignition, and saw again the faint imprint of the strange heritage I'd imagined for her. Like Calum's, her family did indeed trace its ancestry to the Travelling folk, and I'd once regaled her with another romantic notion I'd picked up: that the travellers and tinkers went all the way back to the Iron Age, as itinerant metallurgists tramping the trade routes, making and mending, forging and smelting, giving rise to legends of dwarven mines and of anvils ringing in the deep forest. That she'd found entertaining, if fanciful. Calum's tale of a conscious conspiracy, a genetic and memetic heritage of secret doctrine, would be a different matter. I forbore, again, to mention it.

I forbore, too, to mention something else in this connection, which had been on my mind for some time.

Gabrielle was now a postgrad at the Stem Cell Centre in Edinburgh's BioQuarter; I'd had a string of freelance gigs for science websites. The BioQuarter's energetic biomedicine PR person, Nicola, had her desk in the centre, from which she sent out a steady stream of intriguing snippets about the latest developments. Naturally, I grabbed every opportunity to interview her or pump her for information, partly because she was a good source, but mainly in order to drop by at Gabrielle's desk and have a coffee and chat on the way out. Nicola and I got on well, and I often managed to wheedle out of her some telling detail or curious anecdote that wasn't in the official release. One morning in June, Nicola had trailed the scent of some infertility testing breakthrough, and I'd duly turned up to check it out.

'Hi,' Nicola said, as I put my head round the side of the door of the open-plan office where she worked. She stood up, swept a sheaf of papers and a phone from her metre of desk space, and nodded sideways. 'Coffee?'

I followed her past a couple of proper office doors and into a wide corner with non-glass walls lined with drink and snack machines, and containing a dozen high and low tables interspersed with barstools, random sofas and strategic beanbags. Nicola led the way to a small round table not occupied by a huddle of researchers, left me staking a claim on it, and returned with a couple of steaming plastic cups.

'Thanks,' I said, sipping black coffee. She knew my tastes. We made small talk for a couple of minutes a weather, traffic a then Nicola shuffled her pack and got down to business.

'OK,' she said. 'Very nice development, just out of clinical trials. A non-invasive fertility testing kit. It's a synthetic biology package, with computational properties. You swallow it, it passes through the urinary tract and picks up molecular markers from the sperm and ova, and if your pee turns blue the next day you don't have any obvious fertility problems.'

'What's the advantage? I mean, don't we already have tests?'

'Yes, but tests involve hassle, and embarrassment, and ... anyway, this will have some uptake. Especially with all the new fertility issues.'

'What new issues?'

Nicola sat back. 'Well, here's one. This is in the technical literature, but for, uh, reasons best known to themselves the researchers aren't too keen on its becoming widely discussed among the general public. At least, not until they've got a line worked out.'

'Really?' I said. 'That sounds like a story in itself.'

'No, seriously. If I tell you, it'll have to be deep background and off the record. If I catch you mentioning it a no more stories from me.'

She sounded serious.

'OK,' I said. 'Deal.'

She mimed shaking on it. 'Right,' she said. 'Well, one of the interesting issues is that some patients are presenting who on all tests seem to be fertile individually, but not with each other. And it turns out a sometimes through various infidelities and divorces and sometimes through consensual arrangements like sperm donation and so forth a that they really are fertile. And the speculation is that some kind of speciation event has taken place without anyone noticing.'

I felt a chill. Speciation. Fuck me.

'How could that happen?' I asked. 'I mean, has it ever been observed in other species?'

'Oh, sure. It was first discovered decades ago in mice when it turned out that certain pairs were infertile with each other but fertile with other partners. What had seemed to be one species a what had always been thought to be one species because they were always found together in the same places and niches and so on a turned out to be two. And something like that may have happened in humans.'

'Now, wait a minute,' I said. 'Mice have, what, how many generations a year? Four? Whereas humans-'

'Yes, it's a theoretical problem,' she said. 'There certainly haven't been genetically isolated human populations since ...' She shrugged. 'The Neanderthals, maybe?' She didn't see me flinch. 'And they seem to have bred back into the mainstream, as we know. It might be something stochastic a a train of chance events a rather than the sort of reproductive isolation we see in animal populations. But whatever the reasons, it is happening.'

'So the human species is speciating,' I said. 'Just when we thought it was safe to go back in the water ...'

'What do you mean?' she asked, frowning.

'Just when the whole idea of race is finally just about totally discredited, it turns out there are other actual species hiding inside the human race! Jeez, imagine what someone irresponsible and opportunistic could make of that.'

'I see how that could be a problem, that's why I think it's kept quiet, but I don't see how it could be used that way,' Nicola said. 'There are no obvious physical markers, nor even subtle ones; it's invisible.'

'But they can be found, can't they, with genetic databases?'

'Oh, sure,' she said. 'That's how people get genetic counselling; people can even look themselves up, see if they're compatible ...'

I stared. 'People do this already? This is a thing?'

'Oh yes. Of course it's not advertised that way, maybe because of that very issue. Just as a personal genetic compatibility prediction.'

'Right,' I said. 'Hmm. Yes, that should make the fertility kits a story of wider interest than I thought.'

'Indeed,' said Nicola, pleased at her work. 'That speciation speculation, though ... uh, like I said, deep background and off the record.'

'Sure,' I said.

I didn't even mention it to Gabrielle. But every so often, I worried about it.