I have seen London desolate. I have seen its streets filled with bodies. I’ve heard sirens and cheers. When they sealed me up in an old tube station, I was ready for isolation. They never told me about the dreams.

I signed up out of civic duty, but also for my sister, Carlotta. I lost her three years ago in the last outbreak. She was two years older than me, and I grew up following in her footsteps. Three days after she died, I stood on a train platform, wondering if I had the courage to leap onto the tracks. Carlotta had left the world, a part of my mind reasoned. Why shouldn’t I follow? A poster on the wall beyond the tracks called for volunteers. A happy medium, I thought. A pilgrimage to the land of the dead.

My daily routine now is a purgatory. I enter the quantum sifter three times a day. Any more than that, the scientists tell me, will risk genetic damage. Within the sifter, I am in every London. Imperial London under Charles XII, Vanquished London under countless flags. Domed London. Iceni London. Londinium-super-Tamisem. I am everywhere, and every pathogen is within me, every permutation of a viral genome. A photon of light, they tell me, can interfere with a possible version of itself. Every so often, the receptors on immune cells can interfere with unreal pathogens. As the sifter winds down, nanites scour my blood to catalogue every antibody and weigh every immune response. Every statistical anomaly goes back to the sifter, narrowing the search terms until the technicians isolate the hotspots.

Once they’ve found one, they stuff me into a plastic suit and send me in for real, letting the wavefunction collapse so that I can get a sample. They give me a day off after that, either out of gratitude or to make sure I’m not infected before sending me back out into the multiverse.

I could handle that, if not for the dreams. Carlotta’s there, you see. She’s on the platform or standing on the tracks, beckoning. She’s always wearing a myrtle green shirt, the one she was wearing on the day we took her to the hospital. I told the technicians about it once, and they warned me to clear my mind before entering the sifter. Thoughts have resonance, they said. Thoughts echo through the multiverse.

I try to keep her out of my mind, but civic duty can take me only so far. I don’t see Iceni or Vikings so much any more. The stations I visit look more and more like my own. Carlotta appears in the crowd, first sporadically, then as a silent companion. The technicians must be watching me on the cameras. They must know that my forays into the multiverse are non-random. Will they pull me out? Is it worth the effort to cut through the welded doors of my prison?

Maybe they’re not watching any more. Maybe they’ve declared my data invalid and written me off. It doesn’t matter. I spend most of my time thinking about Carlotta anyway.

One morning, the sifter is off. I ask the technicians and they tell me there’s no work for me today. I plead with them. I hold a picture of Carlotta up to the camera lens, but they say nothing. I can almost hear them shaking their heads, counting the money they’ve wasted.

With nowhere else to go, I put on the plastic suit and sit cross-legged in the sifter, letting thoughts of Carlotta fill my head, willing my toes and fingertips to tingle the way they do when the sifter comes to life. As if triggered by the thought, energy wells up within me. My vision sparkles, then glows.

I am everywhere, but just for a moment.

I am in a sifter, but not mine. Someone built a sifter on another platform. Sirens blare in the distance.

Carlotta stands before me in a plastic suit. Her breath fogs up her faceplate. She holds a hairless, emaciated figure in her arms. It takes a moment for me to recognize the figure as me, wearing a myrtle green shirt.

“Carlotta,” I say.

“I’ve been waiting,” she says. “There’s not much time. They’re cutting power to the city and sealing it off. I defied orders to come down here. I knew you wouldn’t survive the trip to the shelters.”

Me? Am I the one in her arms or the one standing before her? Maybe I am Carlotta’s dream.

“Do you have the genome?”

“It’s in a flash drive, in your shirt pocket,” she says. “I thought maybe wherever you came from they have a cure.”

I set myself — my doppelganger — down on the sifter pad, reach into that familiar shirt pocket and remove the flash drive. I wave it over the scanner on my wrist. The computer checks the database and returns a list of treatments.

Carlotta reads it over.

“We can synthesize at least two of these. My God, if we had only thought to —”

“Don’t worry about the what-ifs,” I say. “Just call somebody. Maybe there’s still time to head off the evacuation.”

“Yes, but what about —?”

I hear the sifter wind down behind me. Without looking, I know it’s empty.

“The technicians will know what to do. Hell, they might find my alter ego a more grateful and willing subject than I ever was.”

Carlotta and I climb the steps and walk past the card readers. Clams cards, not Oysters, but I’m in no mood to quibble over details. Carlotta is here. Wherever here is, I’m going home.

“Where to?” I ask.

Carlotta turns to me.

“I hadn’t thought about it. I signed up because I couldn’t bear to see you wasting away. I wanted the nightmare to end. I never expected …”

“The dreams?” I venture. Carlotta nods.

London awaits us, a stricken city waiting to be reborn.

The story behind the story

S. R. Algernon reveals the inspiration behind Dreaming in 4n Londons

Dreaming in 4n Londons is the third story I’ve written that uses the quantum sifter, after Election day and The meme hunter. The principle behind the sifter is simple. It allows you to search the multiverse, with an infinity of worlds to choose from, but in order to use it effectively, you must discover the search terms that narrow down that infinity so that it contains only the worlds you want to find. As in my earlier stories, the sifter works best if you guide it without trying to force it.

I wrote this story near the apex of the first wave of the COVID-19 pandemic, and I remember thinking that the sifter could allow researchers not only to hunt for a cure, but also to hunt for cures to diseases that haven’t reached us yet. Imagine, for instance, if we could find a universe where COVID-19 struck in 2010 or 2015? In those worlds, the cures and the antibodies would already be available. Our protagonist here is tasked with the challenge of finding those worlds and bringing back samples. I chose London in part as a nod to Nature, but also because the city has had so many incarnations over the past two millennia. A search of London in the multiverse would yield a vast array of possibilities. The 4n signifies the four base-pair options in a strand of DNA raised to the power of the number of point mutations that could distinguish between strains of a disease.

The disease in this story is not COVID-19, or probably even a variant of it, but it has the same effect of separating people from each other and forcing them into isolation. Our politics, too, sometimes becomes virulent, driving us to extremes. We look for ways to bridge the gap and remind ourselves of our shared reality. Sometimes, if we are lucky, our dreams, our hopes, and our visions of the future can transcend physical and social distance to bring us together.