The sea cave only reveals itself at the lowest tides.
I've lived on this coast for thirty-two years, walked this beach a thousand times. I've never seen it before. The entrance hides behind a tumble of rocks that usually sits underwater, accessible only when the moon pulls the Atlantic back far enough to expose the dark mouth in the cliff face.
Today the tide is the lowest it's been in a decade. Something about lunar cycles and atmospheric pressure, I know the science, could explain it in precise terms if anyone asked. But standing here with saltwater soaking through my wellies and the wind whipping my hair into a red flag, science feels inadequate.
The cave calls.
That's not scientific. That's not rational. But it's true.
I should be at the research station. I have data to log, samples to process, a grant report due next week that I've been avoiding because writing about kelp restoration somehow feels less interesting than watching kelp actually restore.
Instead I'm climbing over wet rocks toward a hole in the cliff that looks like it could swallow me whole.
"This is how horror films start," I mutter to no one. "Woman alone. Mysterious cave. Probably something terrible inside."
The rocks are slippery. I nearly fall twice, catching myself on sharp edges that scrape my palms. A sensible person would turn back.
I haven't been sensible since Brendan left. Or maybe I've been too sensible, that was his complaint, wasn't it? Too practical. Too tied to this place. Too unwilling to want more than salt air and a cottage by the sea.
The cave mouth yawns before me, darker than it should be given the afternoon light.
I go in anyway.
Inside, the world changes.
Sound muffles, the crash of waves becomes a distant pulse, the wind barely a breath. The cave walls gleam with moisture, phosphorescence painting the stone in pale green light. It's not large, maybe twenty feet deep, but it feels ancient. Sacred. Like stepping into a church built before churches existed.
And there, in the center of the cave floor, something that shouldn't exist.
A sealskin.
Not a dead seal. Not a carcass. A skin, perfect, whole, laid out as if someone placed it there deliberately. Grey and silver in the dim light, thick and soft-looking. I've studied marine mammals for a decade. I know seal pelts. This isn't a natural shed; seals don't shed their entire skin intact.
A flush of adrenaline, hot and unwelcome. I tell myself to stop being dramatic.
"Probably someone's weird art project," I say aloud. My voice sounds strange in here, absorbed by the stone. "Or a prop. There's always some eejit making documentaries about selkies for the tourists."
Selkies.
The word settles into the silence like a stone into water.
Gran used to tell me stories. Seals who shed their skins and walked as humans. Women taken by fishermen, men who seduced girls on moonlit beaches. The skins were the key, hold the skin, hold the selkie. Keep them on land forever.
Fairy tales. Old wives' tales. The kind of nonsense that kept children away from dangerous waters and gave lonely sailors something to blame their wandering hearts on.
I don't believe in selkies.
I don't believe in anything I can't measure, quantify, examine under a microscope.
I should leave the skin where it is.
That's the smart thing. The scientific thing. Document the location, take photographs, maybe come back with equipment to analyze it properly. Determine whether it's real seal hide, theatrical prop, or some kind of elaborate hoax.
Instead, I reach down and pick it up.
The moment my fingers touch the pelt, I feel it. Not physically, the cave doesn't move, the air doesn't change. But a lock turns inside my chest, some mechanism I didn't know existed, like a key turning in a lock I didn't know existed.
The skin is warm.
That's wrong. It should be cold, lying on stone in a sea cave. But it's warm like a living thing, soft under my fingers, and I can't make myself let go.
"What are you?" I whisper.
No answer. Of course no answer, it's a skin, just a skin, just a confusing and probably illegal piece of marine biology I should report to the wildlife authorities.
I wrap it around my arm and turn to leave.
He's standing at the cave entrance.
Silhouette at first, tall, male, blocking what little light filters in from outside. Adrenaline floods me, cold and immediate. I'm alone in a cave with a strange man. I'm holding something that might be valuable. This is exactly the kind of situation Gran warned me about, though her warnings involved different kinds of predators.
"That's mine." His voice carries through the cave like water, low and resonant. "You found it."
"Who are you?" I demand, and I'm proud that my voice doesn't shake. "How long have you been watching me?"
He steps forward, into the phosphorescent glow, and the air leaves me in a rush.
Beautiful is the wrong word. Beautiful is for sunsets and mountain ranges and art that hangs in museums. This man is something else, all severity and pale skin and eyes the color of deep water, grey-blue and bottomless. His hair is dark, nearly black, slicked back like he's just risen from the sea.
He's also naked.
"Christ," I say, looking away. Then looking back, because I'm only human and he's, god, he's, "Are you having some kind of episode? Should I call someone?"
"I've been waiting for you to find it." He ignores my questions, takes another step closer. Water drips from him, pooling on the stone floor. "Twenty years, Saoirse. I was beginning to think you'd never come."
My name, worn smooth in his mouth like a stone held too long.
He knows my name.
I clutch the sealskin tighter, some instinct screaming that I should not let it go, not now, not ever.
"How do you know who I am?"
"I've watched you." He says it simply, as if it's not absolutely terrifying. "Since you were a girl running on the beach. Since you were a young woman crying over books. Since you walked into the water three years ago and I thought..." His voice cracks. "I thought I'd lose you before you ever found me."
Three years ago.
The night Brendan left. The night I walked into the waves with no intention of walking out, until the cold shocked me back to my senses.
No living soul knows about that night.
"I don't understand." My voice is small now, lost. "What are you?"
He gestures to the skin in my arms. "You're holding the answer. You know the stories, Saoirse. Your grandmother made sure of that."
No.
No, this is impossible, this is insane, this is...
"Selkies aren't real."
"They are." He's close now, close enough that I can see the individual drops of seawater on his skin, the way his chest rises and falls with breaths he doesn't quite need to take. "I am. And you hold my skin, which means, by the old laws..."
"You're mine." The words surface before I can stop them, dredged from stories I heard before I knew what they meant.
His smile transforms his face, something like relief and hunger and years of waiting all wrapped into the curve of his lips.
"Yes," he says. "Finally. Yes."

Nereus Tidewater
I found his sealskin. In selkie lore, that means I own him. He's been waiting.