“Duck, duck, duck,” says Maddy, touching each head in the circle with a perfunctory authority. “Duck, duck,” she pauses almost imperceptibly at the curly, blonde head in front of her, “alien.”

The owner of the curls, Rebecca, scrambles to her feet as Maddy tears off round the circle.

“Go, Maddy; go, Maddy; go, Maddy,” the other children screech, their voices getting higher and more feverish as Maddy passes the empty space and starts on her second lap around. No one cheers for the little blonde girl. No one wants the alien to win.

“Go, Maddy,” yells Candice, along with the others, feeling the tightness in her chest, her hands making little crescent moon marks in her palms. The alien is gaining on Maddy, despite her head-start. Its arms look longer than they should stretching out, stretching out… as Maddy skids into the vacant spot and fills it with her warm, panting body. The circle is complete again.

Rebecca stops. Her face is red, and there is a little bit of spit at the corner of her mouth. Then she smiles and starts walking, a slow measured gait.

“Duck,” she says. “Duck, duck, duck.”

The teachers don’t like this game, Candice knows, but they don’t cross over the expanse of bitumen to the grassed area that skirts the oval where the kids play it at recess time. Everyone plays it now. The climbing frames are desolate in the sun, and the skipping ropes and footballs are left in the sports cupboards.

The teachers don’t like the game, probably because they don’t like to talk about the aliens at all. Candice’s mother doesn’t talk about them either. Her eyes went all shifty, and she got a worried crease in her forehead the one and only time Candice brought it up. She switches off the news when Candice is around, but Candice knows anyway. The kids all know.

The first sign of turning into an alien is that your eyes start to look like glass, all reflective and shiny and hard. And you are cold, cold, cold, because something different is happening to your blood. The last, and final, sign is that you start to go transparent, so that you can see your veins and bones and intestines and gross things through your skin. Candice doesn’t know what happens after that. She knows that they quarantine you and stick you with needles and probably try and get you to tell them where the other aliens are and what plans they have for invading the earth.

Candice looks toward the teacher-on-duty, standing near the classroom under the shade of a large box tree, every green leaf glinting. Candice doesn’t wear a watch, but all of the kids know by some kind of internal instinct that recess time is nearly over. The game has picked up an added urgency. A dark-haired girl from the grade below Candice trips on her way round the circle and only just avoids the alien. She looks like she is going to cry.

When the siren goes, all of the kids will scatter like ash to the wind, helter-skeltering back to the school buildings. If you are stuck being the alien at that point, you will have to be the alien all day. No one will want to sit next to the alien or pass notes to it or walk home with it. Even the teachers, it seems, somehow can detect the stench of alien and will respond to it with a distaste that is almost, almost, but not quite, concealed.

Candice knows that the aliens have an “R nought” of exactly one. She doesn’t know where she heard that, but she knows what it means. It means an alien will always pass it on to just one person. An alien might have contact with many people, but it will only go “duck” and “duck” and “duck,” until it finds the one person who is exactly and only right.

You didn’t show that you were an alien immediately. There would be a time when you were still yourself, but you were really an alien, but you didn’t know it. Maybe you just felt colder inside, cold, cold like her Dad’s hands when he’d clutched her when he picked her up on Friday because it was his weekend with her.

He’d been cold, and his eyes had been glinty and distracted all weekend, and when he dropped her at school Candice had felt all sad and lost although she didn’t usually–usually it was fine.

Maybe you would feel cold, and maybe everything would look sharper like the leaves on the box tree even from so far away, and maybe your blood wouldn’t go in hot spurts anymore but instead be cool and steady like cooled lava–dark and intricate, swirled and ropey.

“Duck,” says Gracie, who used to be Candice’s best friend last year.

Candice looks back to see the teacher looking at her wrist. She can see the little lines cross-hatched in the skin below her eyes and the beads of sweat to the side of her nose, even though the teacher is all the way over near the classroom.

“Duck,” says Gracie, her footsteps approaching, and were they slowing, just a little?

I don’t want to be the alien, thinks Candice. I don’t want to be the alien. I don’t want to be the alien.

“Duck,” says Gracie.

Previously published in Nature Magazine: Futures, February 2016. Reprinted here by permission of the author.