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Éponine doesn't recognize the mermaid, with her gleaming scales and the pearls and bits of abalone shell strung in her hair. She's just like any of the other fancy merfolk who only lower themselves to swim down to the murk when they want some potion or charm or spell forbidden by those who rule the sunlit seas.
She's just another of those folk who turn their noses up at her kind until they have a problem they can't solve on their own -- except that she pauses outside the dark maw of their cave's entrance and hums a little tune to herself, and that startles Éponine so badly that every bioluminescent organ across her scales flares to life with a cold, blue light, because Éponine knows that tune.
The maid spins, startled but not afraid. She squints through the dark waters. Her vision was always terrible, too well adapted for the sunny waters above. It was half the reason Mama always scolded her, as though viciousness could change her nature.
There's no point hiding with her luminescence giving her away. The maid's eyes widen, with recognition and surprise, but not fear.
That's new. Éponine wonders where she learned that. Not in the waters above, surely. The merfolk who swam in the sunny waters were always afraid of every shadow.
"Cosette." Now that she's recognized her, it seems impossible she hadn't. "I didn't think you'd ever come back here."
She'd swum towards the sun as soon as she'd been able, as soon as someone had offered her an escape. Éponine had envied her, but never blamed her.
Cosette's tail flicks, a nervous gesture as familiar as Cosette's hummed song. "I didn't think I would, either." Her gaze darts around, scanning the shadows.
Éponine realizes at once that she was wrong. The song Cosette hummed had been one she'd sung as a child, to bolster her courage. She wasn't unafraid, just trying to hide her fear.
"You're here for a spell," Éponine says, sure. And she's just as certain that when her parents recognize Cosette, they'll make her pay for her spell more dearly than any of the other merfolk, who give their lives or their hearts or their deepest secrets in exchange for a little magic. After Cosette left, Mama had fumed for weeks that she should have taken that merman's luck in exchange for her, or his strength.
"They'll make you pay," Éponine says, a warning. And, because she can't help herself: "Why would you come here?"
"Of course they will. I know how it works. But they're the best."
That much is true. But Éponine steels herself and says, "They used to be."
It doesn't take Cosette more than a moment to understand. She pulls back a little, her expression wary.
Éponine supposes that's warranted.
"There's a cost," Cosette says, because she does know how it works. "What do you want for it?"
She's mistrustful where she was only nervous before. Éponine could reassure her, but she doesn't think Cosette would take her help if she knew it was charity. So she lets Cosette think she's calculating value and worth, rather than trying to keep Cosette from thinking she's being pitied.
"Your smile," Her voice sounds more decisive than it should. Cosette balks for a moment, torn, then presses her mouth into a line and nods agreement, as grim as though Éponine had already taken her payment.
Now's the point where Mama would smile like a shark, but Éponine can't bring herself to do that. She's solemn as she swims around Cosette and guides her toward her cave with a hand on the small of her back. "Come in, then, and tell me what you need."
*
Éponine remembers Cosette's smile. It had always been soft and sweet, the sort that made others return it helplessly. Éponine had envied it as a girl, even as she'd known she wasn't the sort to wear a smile like that.
For the next sevenday, though, she does. Her smile is Cosette's, and merfolk respond to it just as warmly as Éponine had always wanted. But it doesn't feel right on her face, and it chafes like a grit of sand beneath a scale. When Cosette returns to fulfill the bargain, it's a relief to shatter the shell that housed the spell, and return her smile to her.
Cosette smiles at her uncertainly, like she's getting reacquainted with what's rightfully hers, and Éponine smiles back, feeling much the same. It's too sharp to ever be called sweet, but it's her own, and Éponine's glad to have it back.
*
Cosette comes back.
Éponine's as shocked to see her as she seems to be there, but she shakes her hair back so that the pearls and abalone shell glint in the dim light. "I need another," she says, bold and daring. "What's your price?"
"Your sight," Éponine says, and when the spell's completed Éponine goes blind even as Cosette gasps, "Oh, there's so much."
Éponine swims straight for the surface, and spends the next sevenday darting through the bright waters, laughing in delight when the sunlight never hurts her eyes. She almost resents when Cosette finds her and completes the bargain.
Still, it's good to go home, to be able to see home, comforting and familiar in a way the surface never could be.
*
"The shine of your hair," Éponine says the next time she comes, and spends a week with her hair trailing in the current behind her, reflecting sunlight that doesn't exist at those depths.
"Your most prized possession," she says, and nearly calls it off when Cosette returns with a doll fashioned out of seaweed and coral. The last time Éponine had seen it, they'd both been children.
"A memory," she demands, almost vicious, because Cosette keeps coming back. "A good one. Your first kiss."
Cosette goes pink. Éponine thinks the story's going to be great. But Cosette's voice goes distant and wistful as she tells Éponine a different story entirely, of a simple day full of simple joy, and Éponine's so taken aback to realize Cosette's given her payment she can return that she doesn't realize until later that Cosette didn't give her what she asked for at all.
Cosette doesn't even seem to mind she won't be able to give the story back when the bargain's done, and for the next week Éponine's thoughts drift back to the way her face had lit up, like the sun shone down here just for her.
There are any number of reasons merfolk come to barter for spells. But the ones who keep coming back -- in Éponine's experience, it's almost always for love. Love drives people to the greatest lengths, and makes them foolish in the bargaining. The lovelorn and hopeless have always been her family's best customers.
"The name of your beloved," Éponine says, the next time Cosette comes, because curiosity's gnawed her down to the quick, and there's not enough left for kindness.
Cosette hasn't blinked at any price Éponine has named yet, but now, she turns white as bone. "I can't pay you," she says, and before Éponine can respond, she gives a powerful flick of her tail and vanishes into the mirk.
*
Éponine doesn't see her again, for long enough that she thinks she won't. Currents roll in and out and in again and the weeks add up, so that when Éponine swims home one day and finds Cosette there, lingering in front of her cave and twisting her hands, she comes up short in surprise.
Cosette turns to her, though Éponine's sure she didn't make a sound. She comes forward, then stops, preserving distance between them. "I didn't pay you," she says, all at once.
Éponine shakes her head, mystified. "I didn't give you a spell."
Cosette's fingers knot together and press against her stomach. "Not that. Before. I told you a memory, a good one."
"But not the one I asked for," Éponine breathes.
"I couldn't."
Éponine finds she doesn't want to think about who Cosette's been kissing, in the weeks since she's seen her. She asks anyway. "And now?"
Cosette bites her lip. She swims closer, as slow as the tide, and yet it seems all at once she's in front of Éponine. Close enough that when the current shifts, it pushes her forward and her skin and scales brush Éponine's. She doesn't retreat.
"I can share it with you."
Cosette's hands are light on Éponine's arms. She drifts in close, then closer. She shuts her eyes, though she can scarcely see a thing down here anyway. Her mouth brushes Éponine's, soft as a summer breeze.
Éponine grabs onto her without thought. The memory of her first kiss, she thinks.
The name of your beloved, and Cosette had fled, though nothing else down here had frightened her.
Only love brings merfolk back down, again and again.
Éponine pulls her close, and kisses her back, and it feels like sunlight pouring over her, warm and brilliant and blinding.