Castle has arranged everything. He's got a theme, most of the decoration, and he's already sent out invitations (there was even one for Captain Gates, since he's still trying - and failing - to get back into her good graces).

He doesn't think she'll come. But who knows? He remembers that unexpected smile on her face when he gave her the Gemini doll, the warmth in her voice the next day when she talked about Nikki Heat, and a flicker of guilt travels through him for ruining that.

Eh. Not his fault the USB and glass eye were hidden inside the ugly thing. Besides, he's already bought the captain new ones - he's spent a ridiculous amount of money trying to fix this - and she still hasn't forgiven him.

Whatever. He doesn't care.

What matters is: his Halloween party is but days away, and he still hasn't found a costume.

He heaves a deep sigh and drops his chin into his open palm, stares at the open screen in front of him. He's been on websites that he had no idea even existed, peered at geeky stuff and fun stuff and historical stuff, but he's still not sure.

Problem is... He wants them to match.

And he's not exactly certain that Kate will wear any of the costumes he's got his eye on.

The Princess Leia getup is definitely out of the question, as much as he would love that. The Catwoman suit...? He dreamily pictures Kate's smooth lines and curves hugged in shiny black leather, and when she does come into his study, all long legs and gorgeous eyes, and leans over his shoulder, he's too distracted to remember to close his laptop.

"Wall-E?" she says, in that dry tone that he loves. "Seriously, Castle? You're that desperate for a good Halloween costume?"

"Actually, I was looking at-"

And then he stops, shuts his mouth - but it's too late already.

Kate reaches out to scroll down, round breast pressed at his shoulder blade, and he holds his breath, feels a dark strand of hair tingling at his neck. She studies the screen, no doubt noticing that most attires are meant for women, then turns slitted eyes to him.

Yikes.

"What are you doing, Rick?"

Oh, like she doesn't know.

He opens his eyes wide for his best innocent look. It doesn't seem to work too well.

"Nothing," he lies, wanting to press his mouth to the tempting angle of her jaw. She's so close.

"Nothing, really," she echoes, her voice that cold, arched-eyebrow tone that she uses in interrogation. "Because it sure looks like you were in the middle of buying me a costume."

He says nothing, has a feeling he should maybe call his lawyer.

"Castle."

He's never been able to resist her.

"I just wanted us to match," he explains, hears the whine in the words. Not good. "I was... going to surprise you," he says, carefully suppressing the childishness from his voice. "But I haven't found anything good enough for us both."

She opens her mouth and he can see she's not sure which part of that to answer first. She pushes herself up again, takes that lovely brush of a breast away from him as she skirts his desk, hands on her hips.

She spins back to him, a curious look on her face - disbelief meshed with repressed laughter, he thinks.

"You wanted us to match."

He's not sure what's so wrong about that, so he gives a little nod. He did, he does want matching costumes for them. Seriously, how cute would they look as Antony and Cleopatra? Ohh, Antony and Cleopatra - that's a good one-

"Castle. We've been, successfully if painfully, hiding our relationship from everyone at the precinct, including Esposito and Ryan, and even Lanie. And you want our costumes to match? At a party they're all invited to? Jeez, even Gates-"

"Gates is never going to show up," he objects with more confidence than he feels.

"Still, Rick - come on. Wearing matching costumes would be like wearing a neon sign that says, We're together. No way."

He would like to argue. He really would. But he's got nothing.

"Besides," Kate adds, that dark, teasing look flashing in her eyes as she lays her palms on his desk, leans in a little, "I've already got my outfit all figured out, Castle. And I'm not changing it."

"You have?" Excitement flares in his stomach. He remembers that year when she wouldn't even tell him whether or not she was coming - and now she's got her costume planned in advance?

"Uh-huh," she drops, her voice that low caress that always sets his nerves on fire. "And before you even ask - no, I'm not telling."

"Ka-ate," he begs, but she's already pushing off his desk, laughing at him while she steps back into the living-room, hips swaying in the exact same way as they did after that very first case.

Ugh. Frustrating, maddening - he got that right.

But he might have forgotten to mention sexy as hell.

The moment he gets a chance, he corners Esposito and Ryan at the precinct, grills them thoroughly. (Well, he grills Ryan; Esposito throws him a, Why d'ya wanna know? and pretty much walks out.)

Neither of the guys know what Kate's costume will be.

It's so unfair.

He's got a spare key to her apartment. He could sneak in when she's not home, do some snooping.

But he remembers all too well that time when he tracked Alexis using the GPS on her phone, the way Kate reacted, the disapproving look in her eyes. She'd kill him if she knew he was even thinking that.

He likes their teasing game too much to risk it. She wants to surprise him, fine. He'll get his own costume, then, and maybe next year they can coordinate. He wants it so badly; his chest clenches at the thought.

He's never had anyone to coordinate outfits with. Gina would never dress up at all - of course not, it was for children - and the only time Meredith agreed to do it, was supposed to be the Little Red Riding Hood to his Big Bad Wolf, she turned up dressed as Marie-Antoinette instead.

It's stupid, he knows, but years after he still remembers that sharp pang of disappointment, betrayal almost, when she appeared at the door. Talk about foreshadowing.

So he'll wait for Kate. No big deal. She's not going anywhere; she's told him that, showed him over and over again. He believes her.

He can wait one more year for them to be Daredevil and Elektra.

In the meantime-

Oh, yeah. He knows exactly who he's going to be for Halloween.

Ten past ten, and she still isn't here.

He's trying to keep an eye on the door while listening to Ryan and Esposito's conversation, and as a result, he only hears one word out of two. It makes it a little difficult to take an active part in it.

He nervously straightens his jacket, feels the weight of the holster and fake gun under his arm. Seriously, he doesn't know how Bond moves so seamlessly. That thing's seriously awkward.

His eyes dart to the door again.

"Waiting for a special someone, Castle?" Esposito asks in that abrupt way of his, quirking an eyebrow.

Ryan keeps quiet, which is surprising, but right then the door opens and Rick really can't pay any sort of attention to the boys-

Oh no.

Shit.

Seriously?

Victoria Gates walks into his loft, very recognizable despite the fact that her hair is frizzy and tied back at her neck; her arm is hooked around a man's, her husband very probably, a white guy with silver hair who looks in his mid-fifties. He's wearing a summer shirt on top of a long-sleeved tee, a palm tree print that's a little bit ridiculous but also feels strangely familiar.

There's something in his shirt pocket - a plastic toy? Castle can't quite see from where he is.

He makes his way to them, plastering his host smile on his face, and then Gates turns to him and the red leather top she's wearing-

It's all he can do not to burst out laughing.

Right. It's not just any toy in her husband's front pocket - it's a miniature dinosaur. This is awesome.

"Mr. Castle," Captain Gates greets, her voice even and cool as usual.

He's got to admit, she makes a pretty great Zoe. Even though he never would have guessed she was a Firefly fan.

"Captain," he says with a little nod, knowing his mouth must be twisting with the smile he's fighting so hard.

"This is my husband, Alan. Alan, this is Richard Castle, our...civilian consultant."

The way she says the words - it surprises him. There's a sort of reluctant acceptance there, and he suddenly wonders if this is Gates's idea of a peace offering, her showing up to his Halloween party.

"Nice to meet you, Alan," he smiles as he shakes the man's hand, meeting a pair of grey, intelligent eyes. "I like your costume."

Alan smiles back, not embarrassed in the slightest. "Our daughter was the biggest Firefly fan when the show came out; she got us addicted to it. You can't imagine the tragedy in the Gates household when we learned it wasn't renewed."

Castle stares, mouth parted on a laugh that won't come out. "Actually. I might have an idea."

Gates has a defiant look in her eyes, like she's challenging him to comment, but when he says nothing her face softens. Before either of them can speak again, the bell rings, and Rick bolts to the door with an excuse me thrown over his shoulder, certainty curling in his gut.

It's her; he knows it's her.

He yanks the door open - and he's not disappointed.

Kate Beckett stands in front of him, her dark hair gathered up in an elaborate hairdo that has golden beads and pearls dangling from her temples, her eyes made wider and greener by the subtle make-up. Her dress - is that even a dress?

It looks like purple veils artistically wrapped around her body, with a golden bustier holding the whole thing together, matched by bracelets around her biceps, her wrists. There's a scarf knotted around her waist, too, emphasizing the graceful curve of her hips, and holy crap-

Is she Scheherazade? Are the veils coming off for him?

He can't find his voice.

Her eyes twinkle, the only outward reaction she will give, it seems, and she nods at him.

"Can I come in?"

"Uh, yeah," he answers, transfixed, moving to the side. And then he changes his mind, blocks the door with his body. Their chests brush. "Wait. Tell me who you are first."

Kate tilts her head, a slow smile stretching her lips. "Guess, Castle."

He stares at her until suddenly his brain starts working again - and he knows.

"You're Mata Hari," he whispers; her expression tells him he's guessed right.

Shit. How awesome is that?

She's a spy too.

He spends most of his evening watching her.

Not only does she look stunning in her Mata Hari outfit (and seriously, how cool is it that she even knows this shit?) but the way she effortlessly mingles with people, dazzles everyone with her gorgeous laugh - it fascinates him.

She's at the frontier between Beckett and Kate tonight, relaxed and confident, in control, her eyes deep and mesmerizing even as she listens to Patterson's lame jokes, and Castle wishes, so badly, that he could go over to her and wrap an arm around her waist.

Claim her.

This is the woman who loves me.

But Gates is here, her eyes just as sharp as usual despite the couple drinks she's had, and he knows he can't do that.

Probably the reason why Kate's staying away from him, too. She's not taking any chances. He understands, of course. But it still sucks.

He wants to touch her. He wants to curl his fingers at her elbow, feel her skin respond to his.

As if she can read his mind, she looks up, meets his eyes across the room. A tiny smile lifts the corner of her mouth, the dark glow of promise in her eyes, and his stomach twists with his need for her.

The second the last guest is out of the door, he tells himself. The second they're alone together - James Bond is gonna get to know Mata Hari a whole lot better.

"So you liked it?" she asks him, much later, when she's draped over his chest and he can only see the faint outline of her face in the darkness.

"I thought we'd already had this conversation," he smiles, running his thumb across the smooth skin of her forearm.

Her hand lifts over his chest, falls back, and if she meant to smack him she really ought to put a little more strength into it. Not that he's complaining, of course.

"You know I don't mean...this," she murmurs, and he feels the edge of her smile at his shoulder. "You've been pretty - vocal - about how much you like this, Castle."

He grins in the dark, knows she's right. Totally her fault, too. All those veils slowly peeled off, her skin revealed inch by inch.

Times like tonight, he's actually glad his daughter moved out. And that his mother found herself another Halloween party to attend.

"Did you like my Mata Hari outfit?" she prompts when he doesn't answer, lost in fresh, vivid memories of all the ways their bodies fit together.

He hums happily, tightening his arm around her waist, fingers brushing at her side.

"Oh, I did. Very much. Smart. And sexy."

Kate makes that little laughing sound at the back of her throat, pride and pleasure both, and she sighs into his chest, "Good."

God, he loves her so much.

"You know what I liked most about it though?" he says despite himself, wrapping a strand of her dark hair around his index finger.

"What?" she asks, clearly expecting something dirty.

Not what he has in mind, though.

"We matched," he says, trying to keep the satisfaction in his voice to a bare minimum.

He's met with surprised silence, and when she speaks again, her voice is soft.

"Both of us spies," she acknowledges. He can hear her smile. "That make you happy, Castle?"

"You have no idea," he says, knows she can probably hear it all, the goofy, stupid joy that breaks free in his chest.

They didn't even plan it.

Great minds.

"Next year," she murmurs, a kiss brushed to his jaw. "You can choose our costumes, Rick."

His breath stills in his chest. "Yeah?"

"Yeah," she promises, fingers dancing at his chest. "But careful what you pick, Castle. Cause the year after that? It's my turn."