Ingrid had kept them supplied with coffee and Bourbon creams, not joining in the conversation, but giving approving looks at the increasingly feminist tone of Edmund’s diatribe, as his thoughts leapt from Dawkins to Sagan, then the groundbreaking work of Sagan’s ex-wife Lynn Margulis, who first described the origins of mitochondria, the in-cell power-house organelles common to all animal life, and likewise the chloroplasts occurring in plants.

Those organelles, Margulis argued, were the remnants of archaic symbionts, separate bacterial species absorbed but not digested, instead continuing in mutual cooperation.

‘Species can work together instead of fighting,’ Edmund said. ‘Maybe if a man had said it, people would have taken the idea more seriously right from the beginning. Like Beatrix Potter proposing that lichen is a symbiotic pairing of two species.’

‘I didn’t know that,’ Gavriela told him. ‘Is it?’

‘It absolutely is, but the Royal Society didn’t think so at the time, which was why she ended up writing children’s books instead of becoming a scientist.’

Gavriela might never have applied that thinking to computers, but Edmund made the analogy explicit. ‘In a few years, people won’t remember languages like Algol or RPG,’ he said. ‘But bits will still be ones and zeros, and characters will be encoded in EBCDIC or ASCII, or a superset thereof, with TCP/IP at the root of comms. And don’t be too surprised if C continues to run, for decades, if not centuries.’

‘To be fair, some things deservedly die out,’ Gavriela had said. ‘Remember those one-hand card punches? They used to give me cramps.’

‘I hated the blighters,’ Edmund had said, and laughed. ‘And when you only had one chance a day, most likely overnight, for your program to compile . . . These youngsters with their interactive debuggers and the like are just so spoilt.’

And there the conversation took a new direction, but his provocative advice remained; and when she later needed practical hints, Edmund helped in that regard as well. Because new technology would retain its primitive ancestors deep inside, like the chemical powerhouses in every human cell, and if mi tochondria could survive for six hundred million years, surely a few words in plain English could last for decades.

Four days later, Gavriela’s handwritten note was now a .JPEG file, cocooned in self-replicating code that would someday send a POP message to a recipient not yet born.

As always, she had dozed off from time to time during her work. It seemed inevitable that late in the third evening, she came awake to find that she had typed while asleep, hard-coding the message destination in the source code (based on a nonexistent URL, with a device name-value pair that made no sense with current technology), along with the trigger timestamp.

If this code survived, the send routine would activate on the ninth of September, 2033, at 07:30 Universal Standard Time, meaning half past eight if they still put the clocks forward in summer, thirty-four years from now.

Or else the stroke made me insane, if I wasn’t already.

She opened the image one last time to check.

Dearest Lucas,

How wonderful to have a grandson! My words will seem very strange, since we do not know each other and I speak from your past. Still, I must ask you a favour, and be assured it must be this way. Even banks can fail over time, although it is to be hoped that some familiar names survive, so I am forced to contact you in this indirect way, with the hope that you will feel curious enough to investigate as I tell you.

Please, my grandson, look under the parquet flooring, in the right-hand outer corner as you look out the window at the park.                                Love,                                Gavi (your grandmother!)                                X X X

Then she closed down everything apart from a monochrome console window, and fired off a shell file that would send out the first generation of her code package. Like organisms, some would survive to propagate while most would die; but it took only one copy to persist in order to count as victory.

Madness, of course.

The Christmas holidays rolled around, and with them came Brody. Her grandson had put on a little more muscle in addition to the massive increase over the summer, extra mass that suited him, and he had grown a first patchy attempt at a beard, which didn’t suit at all.

It gave Gavriela and Ingrid something other than the fall of the Berlin Wall to talk about. ‘Es ist nicht möglich,’ Ingrid would mutter, ‘dass die Mauer zerstört ist,’ while Gavriela would declare it the death of Communism: ‘Das Kommunismus ist ja kaput.’ Brody’s first term of A-level physics had been too easy, he said, which worried Gavriela a little, because everyone needs a challenge.

He and Amy had joined an astronomy club, which was perhaps an excuse for being together late at night, but seemed also to have sparked a genuine interest in cosmology.

‘I’ll give Geoffrey a ring,’ she told Brody, wanting to encourage him. ‘Perhaps he can get one of his students to show you the particle accelerators.’

It was a well-established principle of labour and autocracy: pharaohs had slaves, academics had grad students. But when she rang him, Geoffrey surprised her. ‘I’ll show you around myself,’ he said, taking it for granted that she intended to accompany Brody.

‘Um, I’ll need to use the goods ramp,’ she told him. ‘Because of the wheelchair.’

‘For you, anything. You can have a dozen chaps bearing you aloft on their shoulders, if you prefer.’

‘Grad students, of course.’

‘Well, yes. Nice to get some use out of the buggers.’

His touch of East London coarseness had the same effect as Ingrid’s formality when speaking German: both caused Gavriela to smile, both made her feel at home.

‘I’ll spare them the effort,’ she said. ‘But I’ll see you tomorrow.’

Next morning, they disembarked carefully from the taxi – Ingrid and Brody helping Gavriela in the wheelchair – and went inside with the college porter’s assistance. They rode up in a lift with Geoffrey, and as a group of four they poked around inside one of the labs, chatting to a researcher who seemed glad to share his enthusiasm for the work. Brody looked fascinated.

Gavriela drifted away, having a ‘senior moment’, before realising she needed the bathroom. Remembering the way, she steered her wheelchair out into the corridor, accompanied by Ingrid.

‘When you die,’ Gavriela told Ingrid for the twentieth or the hundredth time, ‘they’ll make you a saint. You know that, don’t you?’

‘Let’s put off the moment for both of us,’ Ingrid replied. ‘This door here?’

‘That’s the one.’

*

Afterwards, they found Brody in a different lab, left temporarily by himself (which he seemed proud of) after a departmental secretary had dragged Geoffrey away to deal with something.

Brody grinned, showing Gavriela several large colour monitors atop a lab bench.

‘They’re running pattern recognition over your work,’ he told her. ‘And they’ve found a rare astronomical event of some sort. See?’

To prevent people from switching off the processors in mid-run, someone had put a felt-tip-written label beneath one of the monitors.

Property of Project HEIMDALL. Please leave running.

But this was bad. Someone had found her old data of interest. No one was supposed to know what Gavriela had spotted amid the cosmic-ray data. Or did it not matter at this time?

‘Tell me.’ Her voice came out as a whisper.

‘Sure, Gran. See here?’ He pointed at the leftmost monitor, where among scattered white dots, three scarlet points glowed brightly, forming the vertices of an equilateral triangle. ‘There’s the event.’