As she runs, Olivia begins to notice the candles in the giant chandeliers above her head flicker and then sputter and then silently extinguish. At almost exactly the same time, Oliver’s slide enters a tunnel. At first, it seems there is light up ahead. It takes him a few seconds to realize that’s just an illusion. The children’s respective journeys grow darker, as if a giant someone has taken a giant straw to slowly slurp away all the light.

Splash-splash! Olivia’s next step lands her in ankle-deep liquid. She bends down to touch it. It feels warm. She licks her fingers tentatively. Salty. They must be at the edge of an ocean.

She hears a long sploooooshshsh a few meters away, like when she lets go of the rope and slowly fall-glides into the lake after waterskiing.

“Aw crap! My Switch! No no! Please be ok!” She hears a very-familiar voice exclaim. Olivia rolls her eyes.

“Oliver? Are you there?” She calls in the direction of the voice. The sound travels in the darkness, echoes throughout the cavernous emptiness she can feel all around.

“Ola?” Oliver’s small voice comes back at her. “Is that you?”

“Yes, Oli. Walk toward my voice and I’ll walk toward you.” She hears him begin to slosh obediently in her direction.

Presently, a warm glow is dawning, like a yellow morning after a moonless night. It happens so slowly that the kids don’t even notice until they are standing face-to-face and squinting at one another in the near-brilliance. Olivia shields her eyes and looks around to find the source but it’s impossible.

“Ola!” Oliver begins breathlessly. “I saw the slide from the park, but it wasn’t the slide from the park and then I went down it and it went faster and faster and — what?” Oliver pauses. Olivia’s face has a look of pure horror. Something is happening to Oliver. He can feel it, a prickling sensation, like an army of spiders crawling across his body from his back up through his shoulders and down his front. “Ola! Help me!” He yells desperately. “What’s happening to me?!”

Growing along Oliver’s skin in spidery progressions in all directions are green-blue-shiny-slimy scaly protrusions. They don’t stop spreading; The scales spread first in lines like a web and then the spaces between the lines fill in to create a dense covering over all of Oliver’s neck and chest and torso.

“Does it hurt?” She asks him. Breathing fast — too fast — he nods wildly, eyes tearing up. It isn’t entirely true. It doesn’t hurt, exactly… it’s more like a warm tingly sensation, a pricking and spiking but not-painful feeling. His skin starts to become numb all over, radiating out from back to front and into his arms and legs and fingers and toes.

“NO! STOP!” Olivia screams as she begins to claw wildly at the scale-growths with her fingernails. “Get off of him!” She begs. The scales spread — along one arm, then the other, reaching the fingers and the finger tips, each of her brother’s little knuckles gradually growing greeny-bluey-slimy growths. The scales spread gradually down each thigh and through the end of each foot, replacing his clothes until he is just a naked fish-body. (Olivia wonders for one second if his clothes are trapped under those scales. She is pretty sure she can see a bulge where his Switch would have been in his hoodie pocket. She quickly suppresses the thought about whether the scales have somehow grown to accommodate that ridiculous gaming console her brother loves and carries everywhere. How can that matter right now!?) Olivia sees a scaly-shiny fishtail blossoming straight out from her brother’s behind. She sees his hair is gone, too, replaced by a sets of fins sticking straight out of his head. They look hard. They look like they belong on the spine of a dragon.

Chest heaving, tears streaming down her face, Olivia backs away from Oliver in horror. All of a sudden, though, she is distracted by a weird pricking along the grooves of her own palms. It’s as though a fortune-teller with very jagged, long, Cardi B fingernails were conducting palmistry that left behind tiny trails of itchy-tickly poison. She looks down and sees it: scales are growing on her, too. Multiplying, crowding along her finger-creases, creating the same web-shape they’d made on Oliver’s body, creating a web along her veins that gets slowly coloured in. She turns her wrists over. The scales are growing — up, up her arms, to her elbows, shoulders, up her neck and down across her chest, first mapping her collar bone and the outline of her torso and then covering her skin all over in slimy green-blue scales.

A few minutes later they stand in the mysterious glow of the mysterious light, staring at one another: a fish-girl and fish-boy. A pair of scaly shiny blue-green monsters.

At almost exactly the same second, both children realize the liquid that had been around ankle-depth is rising rapidly. Almost too smoothly, as if it were being controlled mechanically, the water level ascends to Oliver’s belly button, then Olivia’s, and then up, up to cover their torsos. Instinctively, they begin to tread water to continue breathing above the surface. Olivia is gulping in big mouthfuls of air but suddenly she realizes something. It feels like she doesn’t actually need to be breathing through her lips anymore. She holds her breath for a minute. Yes, it’s true. It feels like oxygen is coming in through her body somehow. She feels along her ribcage with webbed fingers and there they are: a set of gills, waving in and out as they parse oxygen from the sea water. As a quick experiment, she submerges her whole head, opening and closing her mouth underneath the water. It doesn’t feel like drowning. The gills are breathing for her. She can see Oliver opposite her, his head also submerged. He must just have learned the same thing.

***This is all very confusing and alarming, sure, but at the same time, a deep and abiding and inexplicable calm begins to grow inside Olivia’s belly. She feels like she belongs under the water now. With newly-webbed hands and feet, she maneuvers around below the surface, opening her eyes wide to explore what’s around her in every direction. Little schools of brightly-coloured fish dart everywhere, more fluorescent and vibrant than she can remember ever seeing at the aquarium. Further off, bigger, darker creatures swim and lurk. She thinks she can see the outline of a stingray, a giant king crab, a swordfish maybe.

Olivia turns to ask Oliver if he knows how many species live in the ocean. (She does. It’s over 230,000.)

That’s when she realizes Oliver is gone. She opens her mouth and yells for him:

“OLIIVVERRRR!! OLI OLI!” No sound comes out. A meaningless cascade of bubbles falls from between her lips. Blup blup blubb. Nothing audible. She feels panic beginning to rise in her throat. She knows you can yell underwater. She’s done it a hundred times, playing games in her friends’ backyard pools. She tries again. No matter how much she feels like she’s straining her voice box, she can’t hear a single sound.

Before she can have a proper meltdown about the apparent loss of her voice, she feels a nudge. Right in her left butt cheek. Kind of like being gently head-butted by a pony or a horse or something — not aggressive but definitely insistent. And squishy, a little. She turns behind her and stares straight into a pair of big blue doe-like eyes. The eyebrows are raised insistently, urgently trying to communicate something. Olivia shakes her head furiously. What do you want?! She thinks in its direction. She decides it looks like an underwater horse, except it has a long pointy golden horn sticking out of its forehead. Unicorn, she corrects herself, fully aware of how ridiculous this is. Underwater unicorn. An ocean-unicorn. Olivia still doesn’t understand what it is trying to communicate with the wiggling eyebrows and insistence on its face. She shakes her head to show her incomprehension.

The doe-eyed horse creature rolls its heavily-lashed eyes and whinnies encouragingly as it jerks its head to the side. After a moment, Olivia finds herself understanding. She hears the voice of the creature inside her own head. The voice is like a climpering, high-treble collection of notes played at the far right end of a slightly-out-of-tune piano. The words are clear and urgent:

“Jump on my back! Come on! We have to go!”

“I CAN’T just get on your back because you tell me to!” Olivia yells at the underwater-unicorn. “I have to find my brother!” It comes out like blup BLUUPP blubb blup blub blub! Olivia sees no movement of the creature’s lips, but hears, in that high, out-of-tune register:

“I’ll take you to your brother. You can trust me. It’s okay. I am reliable. I am a helper.”

“Did you just say that!?” More noiseless bubbles rise from Olivia’s lips in the creature’s direction. The ocean-unicorn smiles wryly.

“Yes. I am a human-whisperer. I understand you. I can take you to Mother. My name is Lalibela. And I am a seanicorn in the service of Mother.”

Seanicorn. That makes sense. A seahorse-unicorn. She wonders idly which of the 35 species of seahorse Lalibela might be. More importantly, she wonders: what’s a human whisperer? And who is Mother?

“We have to go now, Olivia. Trust me. You can’t stay here by yourself. Oliver is going to need you.”

How does she know my name? OUR names?

Reluctantly, though, Olivia looks around at the deep, aquamarine water filled with strange undersea creatures stretching in every direction and realizes she really does not have any other options. For all the life bubbling around them, none of it looks even remotely like her brother could be there.

“Here, straddle my back and hold my mane, okay?” Lalibela turns helpfully around. Olivia sees the broad, soft body ends in a curl like a seahorse has, instead of a tail or a butt or rear legs, like you’d expect on a unicorn. She takes a deep breath for courage and places one scaly leg on either side of Lalibela’s torso, then grabs onto the mane with all ten webbed fingers in a very tight death-grip.

Lalibela neighs and Olivia hears “HEY! A little gentler than that! Don’t pull!” So she loosens her grip a little, realizing that the hairs on the mane are kind of like tentacles that wrap around her hands, so she doesn’t have to grip so tightly.

Apparently satisfied, Lalibela turns and begins to glide smoothly, artfully and very decisively in a straight-down direction.

Lalibela and Olivia are in a deep darkness for some time. It reminds Olivia of the train tunnels in between subway stops. Her eyes would stretch, searching for anything at all as she stared out the window from her seat next to their mother on a trip to the dentist or the doctor or swimming lessons or wherever. She always wanted just a hint of what the inside of the tunnel might look like, but there would be no hope of illumination no matter how long she dedicated to staring. This was the same, in terms of darkness, but the difference was Olivia sensed space all around them. It seems the present darkness is caused not by a tight subterranean passage blocking out light but by the reality of absolute emptiness. Olivia shudders and pushes her newly-scaled torso against Lalibela’s back. She has no idea where they are, and she does not like that feeling.