But that was as far as the topic stretched among rational scientists, so Gavriela asked Patrick about his work with the new cryogenics equipment, investigating fluids that could flow by themselves unrestrained by viscosity, or conduct currents without experiencing resistance.

‘Stuff that spontaneously creeps up inside a flask,’ said Patrick. ‘Spooky weirdness at a dimension you can see.’

There were understanding nods all around, because solving Schrödinger’s wave equation was mechanical: as pragmatic practitioners, they ignored philosophical weirdness, and simply put the recipe to work, hoping that someday a new theory would bring forth a more reasonable metaphor. Counter-intuitive quantum phenomena, challenging concepts as basic as cause and effect, were unsettling in objects you could hold in your hand, although in this case you would need a massively insulated gauntlet.

After the meal, Anders gave Patrick and Gavriela a lift in his new Morris Minor – for propriety’s sake, dropping Gavriela off first. But she paused in the redbrick porch with the stained-glass panel above the front door, waiting for the Morris to drive out of sight, and her escort team to pull up at the kerb.

Only then, with her protection, did she go inside.

An empty house reveals itself by lack of vibration, but there is such a thing as self-deception, not to mention bombs and timers, so they went through the place – tonight they had been too overstretched to leave a watcher on guard – and at first found nothing. But during the second pass—

Oh, no. Don’t bring children into this.

In the bedside drawer – how had Dmitri, if it was Dmitri, known she would check there first? – she found a glossy monochrome photograph featuring a youngster and two adults, and she might have ignored it except that the schoolgirl, some eleven or twelve years old – around Carl’s age – was like her brother brought back to life: Erik’s features in feminine form.

With Ilse, Erik’s wife – widow, and it was a surprise that she had survived – standing alongside a smiling Dmitri Shtemenko, they looked like a family group. Gavriela wished she could believe it to be technical trickery on the KGB’s behalf, instead of what it seemed: Dmitri, so monstrous, in her dead brother’s place.

And Gavriela had a new family member: for niece, read hostage.

So when are you going to make your move?

But if Dmitri were intending to exert pressure on Gavriela, recruiting her for his Soviet masters, there was a way to neutralise the threat: render herself unsuitable. In operant conditioning terms she now had both positive and negative rewards awaiting, should she choose to resign: returning to her first love, and avoiding the betrayal of her adopted country.

Assuming that was Dmitri’s intent.

Term-time came and with it the end of the operation, without results, since Gavriela had said nothing of the photograph she finally burnt, an action she regretted afterwards. Back home with Carl, and with moving house inevitable even if she stayed in her current job – because of the organisation’s westward relocation – she made her decision, and went to talk to Russell Sheffield, the head of section to whom she reported.

From behind his desk, he listened to her explanation as he whittled through his unlit meerschaum with a flexible pipe-cleaner. In the past, he had often given her unused pipe-cleaners to take home for Carl: they were excellent for creating geometric framework shapes, though her attempt to explain a hypercube had been premature. Perhaps when Carl was older.

‘I found an old acquaintance working at Imperial,’ she said, ‘who’ll put in a good word for me. And they’re actively looking for researchers.’

Lucas Krause, last seen heading off to the States with his new wife during the war, was back in London and settled down. It would be strange to have a link to her student days, all the way back to attending her first lecture and Professor Möller with the flowing white hair and the spectacular demonstration with the tall wire basket.

‘I rather considered that kind of thing myself, returning to the halls of academe’ – Sheffield looked up from his pipe-cleaning operation – ‘when I was younger.’

‘Point taken, sir.’

At least he had not insulted her by dragging out the matter of her pension, and the extent to which it might be reduced by her departing now. But she was not the only one making big decisions: the atmosphere around the place, as work-in-progress files went into archive cases for transportation to the new site, was very odd, with choppy conversations and unsettled expressions everywhere.

‘If you’re truly certain’ – he put down his pipe, stood up, and reached out across the desktop – ‘then I’ll shake your hand and wish you the best of luck, old girl.’

She stood up, and they shook.

‘You know I—’ But there was no way to complete the sentence.

‘After they kick me out of this place, I’ll be tending roses,’ said Sheffield, ‘or pushing up daisies. Certainly not good for anything else. I do believe I’m rather envious.’

Gavriela gave a sad laugh.

This was a lot like leaving home.

On her first day at Imperial, walking beneath an open window of the Royal College of Music, she heard a breath-catching rendition of a Mozart piece for string quartet. Across the road reared the dome of the Royal Albert Hall, where perhaps the students would play one day, if they hadn’t already. As for her, this was like the first day of term, a new beginning – like Carl off to school in his cap and gaberdine raincoat, satchel and plimsole bag slung from one shoulder – except that she had an old friend waiting for her in the Huxley building reception: Lucas, his once-curly hair now receded and merely wavy, controlled by hair-tonic. She could smell the Silvikrin.

‘Gabrielle.’ It was a good start, remembering not to call her Gavriela. ‘I’ll show you to your office.’

They shook hands while the porter watched, though Gavriela would rather have hugged him.

‘How’s your wife, er—?’

‘Enjoying Nebraska,’ he said. ‘Come on, we’ll drop off your coat and you can meet everyone.’

Upstairs, she found that her room was pokey, featuring a scarred desk maybe half the size of the one she had used in Eastcote, with cardboard folded beneath one leg for stability.

‘It’s wonderful,’ she said.

A stack of loose-leaf pages bore columns of figures with headings like Declination, Azimuth and Peak, along with pencil-drawn graphs.

‘Readings from the old instrumentation,’ said Lucas. ‘You’ll have plenty of your own soon enough.’

‘I’m sure.’

‘Most of us really aren’t that good at stats.’ Lucas meant statistical analysis ‘Good luck on plucking meaning out of that lot, but the rest of us can’t.’

He was not really talking about the data; it was more an oblique acknowledgment of her time spent on work she could never discuss, for most of the eight years since the war, a gap she would have to fill with fiction as far as her other colleagues were concerned.

The strange thing was, as she fell asleep that night, she half-dreamed of deciphering a pattern in just such data, though not now, not yet: something do with meson detection and an equilateral triangle that could not be explained, yet neither could it be ignored. An insight she would keep to herself . . . A comforting thought, as she drifted further into sleep.

Secrecy kept her safe.

ELEVEN

LUNA, 503970 AD

Crystalline and serene, Roger and Gavriela held hands as they stared up at the crimson-banded disc of Earth. To him it was the species’ birthplace, an ancestral home, but she had been born and lived her organic life there, half a million years ago.

—What do you think is going to happen, Roger?

—I’ve long given up trying to read Kenna’s mind.