One night in the vault, as we stood below the polyamide canopy clutching hands, I told him that I would never let him go -- he, the brightest of us all, he who was to save the world.

He smiled, that sweetest of smiles, and said: Before all this is done, you'll be safe and sound inside me.

I don't care, I said. I want to see it finished with my own eyes.

His hands were cold as ice, as all our brightest's were. I put my head against his chest and listened to the liquid helium within. He was working, even as we spoke. But he betrayed no sign of his labour. Instead he laid his chin on my head, and took me into his arms, and said that everything could be saved given enough time.

But we are running out of time, I said.

It was true. Things used to be so simple, but now the skies were wreathed with smoke; already the first coastal cities had begun to burn. Ours, with its reinforced shell, would last longer than most; but eventually even the canopy would crack, and the whole project would come crashing down over our heads. Only him -- and his brothers and sisters, toiling in the cities beyond -- would be left to save what we had left behind.

He must have noticed my discomfort, for he drew me upright, and asked: Would you like to see my work?

And I nodded yes, because I had begun to feel the immense tragedy of it all. The world would keep on spinning, outside, even as the smoke was thickening, no doubt faster than our drives could write; we are forgetting, all of us, all of the time. Moments passing through our fingers like sand.

Show me something good, I told him. Show me what all this has been for.

So he turned on the console. In an instant, the canopy was flooded with colours, flickering from red to burning blue. Of all the things he had started with, he had saved the shades of sky. In the midst of it all hung an array of little white wisps, bleeding stray dots into the wind.

He waved the faulty rendering away with a flick of his hand. It is a work in progress, he said.

It's beautiful, I said. The next words I wanted to add did not leave my mouth, but I suspect he guessed at them, for he threw his head back, and his breath formed little clouds in front of his face, drifting away like the pixels on the screen.

Thank you, he laughed. That is very nice of you.

I asked, in my mind, if there would be room under that sky for a boy to clutch his lover's hands. Would there be room in the vault, beneath his miles of humming ice? Would there be room for two under the canopy still, even as it burned?

Instead, I asked: Can you show me more beautiful things?

He thought for a moment, but seemed to not find the right words. Instead he said: I can show you where I keep them.

He took my hand, and we descended through the archives, past the ventilation shafts, past the great steam-trunk arrays nestled deep into the city's floor. At the deepest point, he slid open a heavy panel. Servers blinked in the dark, caked in frost. Liquid helium hummed beneath our feet. I shivered; he kept his arm around me, though he knew it did not help.

There will be room to save it all, he said. Each unit can hold a thousand skies; each rack, ten thousand. There are a hundred thousand racks in all. There will be room for all my skies -- and clouds, and trees and fish and birds, and hands to hold and faces to touch, and souls to fill it all.

He explained it all, with hardly a hint of sadness, though I thought I saw his throat bob, and the lights in his eyes dim. You'll be safe with me here, he said. But it is not quite done yet.

He led me down the corridor, turn after turn, and the air grew colder with every step. I began to fear that the blood in my fingers would turn to ice. We reached a place where the racks ended, at a sunken plexiglass panel in the middle of the floor.

Look down, he said.

I followed his gaze. There, the golden helium-cooled chandeliers hung suspended from the plastic below us. They glistened in the service lights, tapering in tiers towards their rubidium tips. At the lowest point of each hung thin beams of light: from them hung the shape of his multivariate heart.

He said: Here we will have our room. After I have saved the world, I will solve the question of us. Our question will live on in the quantum dots, in my glittering lattices, below my miles of humming skies.

And he said: We will exist in the afterlife -- which is to say, the set of all possible futures in which we exist forever.

How, I asked, how can something like this exist forever? How has something so close to your heart remained undone?

The parameters are incomplete, he said.

And he drew his face to mine. Cold copper pressed to my lips. My mind whirred. The lattices below us hung in silence. I thought I saw them twinkle, and I imagined our kiss spread into innumerable superimposed stars, etched into the gaze of the crystal chandeliers, spinning into the discs of sky.

If not all moments could be saved, then at least this. The beat of my heart, the shimmering optical lattices, our kiss unfurled into butterfly-winged amplitudes in his heaven. Our love, a waveform, forever entangled in the depths of a glittering restless heart.