"Beckett?" his voice comes tentative around the door of the break room and Kate bows her head at the counter, eyes slipping closed. She knew he would follow her when she stalked away from the captain, felt his eyes on her back as she did her best not to stomp into the break room and slam the door behind herself.

It's an honour, to be given this case. A demonstration of how much the mayor values her work as a detective, and a chance to prove that her shooting hasn't lessened her abilities as a cop in the slightest. Even so, frustration bubbles up in her belly and she grits her teeth, tucks the spill of her hair back behind one ear.

A slow breath in through her nose, another, and then she squares her shoulders and turns to face her partner. The moment he sees the set of her jaw, Castle steps inside and closes the door behind himself, leaning back against it with his hands pushed into the pockets of his slacks. "Is this. . .are you okay?"

A sigh makes it halfway out of her, crumbling in her mouth before it can really escape, and Kate comes away from the counter. The coffee is just starting to percolate now, the smell so rich and good. The better for having come from her, rather than needing to rely on him to work the wretched machine, and for a moment she wants to turn her back on him once more in smug satisfaction.

That's childish, and if they're going to make it through this they have to learn to cooperate.

Beckett takes a couple of steps towards Castle and shrugs, folding her arms awkwardly across her stomach. She's hyperaware of the arrangement of her bones, feels like it's Natalie Rhodes all over again, and Kate shakes herself right out of the drag of melancholia. "I'm fine."

"We don't have to do this if it makes you uncomfortable," he offers, peeling himself away from the door and reaching for her, two fingers circled at her wrist to bring her with him over to the couch. It reminds her of last week, her body tugged along in the wake of his, and she braces for the cold press of a metal bracelet that never comes.

Sinking down to sit, Kate folds one leg over the other and clasps her hands, rests them against the rise of her knee. Castle is fidgety next to her, picking at the button hole on the cuff of his shirt where a thread is just starting to unravel. It irritates her and she huffs, tension humming like white noise in the hard set of her jaw.

"Castle, we don't have a choice. This is the mayor's cousin. I would have thought you'd be eager to get justice for her, what with you being his friend and all."

He grumps at her, turning his face half away in exasperation, and she wonders if their entire marriage is going to go like this. Both of them hurting, both of them reluctant to communicate and just be honest. "Of course I want to get justice. I just don't want to do it at your expense. And I can't-"

"Can't what?" Kate asks when he falls silent, knotting her fingers together so she doesn't reach for him instead.

Scraping his hands over his face, Castle sighs into the cup of his palms and turns to look at her again. "I can't bear to pretend to be married to you, knowing that it's making you miserable."

She feels it like a blow to the solar plexus and her mouth drops open, throat working over silence. Since the summer, Kate has been carrying his words around with her, kept close in a secret space inside her chest. Someplace she dips into whenever she needs that boost, whenever loneliness swarms black and noisy as a plague and she half expects to be struck down for her dishonesty.

So yes, she knows. She's known, all this time. Castle is in love with her.

And the mayor wants them to go undercover as a married couple.

"Rick," she starts, and it has him jerking towards her, eyes snapping up to meet hers. They're going to have to get used to using each other's first name, and quickly, but she can't escape the memory of it like ash in her mouth as he hoisted her into his arms, the raw scrape of desperation up her throat as her partner hustled her away from that hangar. "I won't be miserable. And I can't think of anybody I'd rather do this with."

The offering, timid as it might be, has his whole face breaking open around a grin, his skin luminescent with pure and lovely joy. Just last week, he said he wants to get hitched to her, and the way he had stumbled to correct himself had been adorable, her heart sticky and malleable against her ribs. She let him have it gracefully, pretended she wasn't holding the truth of his desire in the cup of her palms, but she knew.

He can see them getting married someday. Wants that, for them.

"And the. . .the baby?"

"Fake pregnancy," she corrects immediately, automatically, despite the fact that she still can't believe she actually agreed to do it.

The mayor's cousin was the fourth woman to die in suspicious circumstances at the gated community where she lived. The fourth woman from a group of mothers that meet a couple times a week. So to get in to the mommy club, Kate has to fake a pregnancy.

Bump and all.

"I don't want you to be uncomfortable," her partner says quietly, drumming two fingers against the hard edge of his knee now. He's a good man, patient and kind, and tenderness wells up in her belly when he lifts his eyes to meet hers.

Shaking her head just a little, Kate manages something close to a smile for him. More the lift of one corner of her mouth than anything else, nowhere close to the way her lips peeled apart around her happiness in that bank last month, but it has an echoing curve wriggling its way across Castle's mouth.

"It's gonna be strange, I won't deny that. But I've had to do worse things undercover before. Spending some time in a beautiful house with my partner doesn't seem so bad, even if I have to wear a fake stomach."

"What if we end up having to stay for Christmas?" he blurts, clapping one hand over his mouth. His eyes widen, something charming and youthful about the abashed wriggle in his shoulders. Like a little boy who knows he can flirt his way out of any scrape.

They've never done the Christmas thing, never exchanged gifts or anything like that. He came to the precinct's party that first year he was shadowing her, but then the next year he was at a Black Pawn party with Gina instead. And they. . .they haven't talked about this year. What their plans are.

It's too close to somewhere they aren't yet, too much like your family or mine.

Kate picks at the ragged edge of a nail - she caught it on the thick knit of her scarf on the way out of the door this morning - and heat blooms high up in her cheeks, along the pale column of her neck. "We'll have a couple of weeks before Christmas comes around, and I'm hopeful it won't take us that long to figure out what's going on. But if we don't, if we're still there, then I guess we'll just have to spend it together."

"I've never spent the day without my daughter," he gruffs, but there's a flare of hope in his face too. Horror at the thought of being apart from Alexis warring with his yearning to spend Christmas day with her, Kate Beckett, and she has to turn her face half away from him. "But I'm sure we'll solve it by then anyway. It's what we're great at."

"There might be nothing to solve," Beckett says, her words snaking out like a tether to wrap around his middle as he descends to the depths of mystery and intrigue. There's no evidence of a crime at all here, just a string of apparently accidental deaths, and that's why the mayor came to them.

Nobody else will listen. Not the way Castle does.

Her partner lifts one shoulder at her in a shrug, the scruff that peppers his jaw making her mouth dry for just a moment, tongue sticking uncomfortably against the back of her teeth. He's handsome in the winter, the bite of the cold making his skin pale and his cheeks flushed, life pulsing so vibrantly just underneath his skin. It makes him stick close against her side, too, sharing body heat, and so many times she's wanted to reach for his hands, curl her wind-chapped fingers up against the warmth of his bear paw.

"I know, but I owe it to Bob to at least find out what's really going on. Without him, I never would have gotten to be your partner."

"We both owe him a lot," she offers, ducking her chin so that the curtain of her hair swoops forward to hide her face from him. Like the end of a great performance and she waits for the crescendo of rapturous applause, in appreciation of how valiantly she pretended to be unaffected.

That's over with now, finished. If she's going to be his wife - even as a charade - she won't be cold and aloof like so many of the women they come across, won't turn away from how he yearns to love her. If they're going to do this, go undercover, she's going to sell it.

Let everybody see how much she loves him right back.

The knock at her door makes her smile where she might once have startled, his knuckles against the wood familiar in their merry little dance, and she walks - waddles - across the living room to answer it. Her suitcases are packed, two of them because they're supposed to look like they're moving in, and she brushes her fingers over the handle of one of the bags before she opens her door to him.

She was ready for a reaction, knew it couldn't exactly go unnoticed, but Castle stumbles and catches himself against her doorframe, looks for a moment like he's about to sink slowly to his knees before her. A hand settles reflexively against the top of the bump and she steps back from the entryway to let him inside.

Her entire suitcase is filled with clothes that aren't hers. Well, okay, they do technically belong to her, but she's never worn them before. Won't ever again once this case is over.

Yesterday, after she squared her jaw and scuttled, tail between her legs, back to Captain Gates' office to receive the rest of her briefing, she went shopping. Dragged Lanie along with her, because Kate Beckett does not know how to dress like somebody's suburban wife, or like a pregnant woman, and she needed somebody to gripe at.

It's freezing outside, although they haven't gotten any snow yet this winter, so this morning she bundled up in a grey knit sweater, a wool coat that's a mixture of white and paler grey. The layers don't do much to hide the bump - she's supposed to be six months pregnant - and Castle takes a long while to drag his eyes up to her face.

"That's. . .kinda weird."

"Yeah," she snorts, but all the same she can't help the defensive flit of her hand against the roundness of her fake belly. There's no baby in there, no fluttering proof of life, but still she feels protective. Silly with it, and a flush burns in her cheeks. "I think I'm going to end up recycling four of the same outfits. It's hard to buy a whole new wardrobe of things you wouldn't normally choose."

"I've never seen you dressed anything less than perfectly."

Her mouth opens to remind him that he's seen her in pajamas, seen her in nothing at all when her apartment exploded, but the more sensible part of her brain puts a noose around her tongue and pulls tight. She's pretending to be his wife, yes, but she is so not ready to hear however he might respond to that.

You looked perfect even then, his voice says in her head, low and gravelly, and she feels the heat of embarrassment flare in her cheeks, along column of her throat.

Castle doesn't seem to have noticed; if he has, he's gracious enough to ignore it. Shaking his head, he moves further inside her apartment and extends the handle of her rolling suitcase, dragging it a little way towards the door before he turns back to look at her. "You ready to go?"

"As ready as I'm ever gonna get," she says, a smile blooming when she meets his eyes, and he grins right back at her.

Kate tucks her purse over her shoulder and curls her fingers around the handle of the smaller case, pushes it out into the hallway ahead of herself and turns to lock her apartment door. A little way down the corridor Castle hovers with her bag, and when she comes back around to face him he's not quite fast enough.

The look of terrifying awe lingers a moment too long on his face and Beckett swallows back the flood of strange grief, sucks in a breath before she goes to him. He chuckles at her and when she gets close enough - it takes a while - she swats at his arm, the very tips of her fingers lingering to flirt with the material of his sweater. It's a deep green, pushed up to his elbows, and for a moment she wants to lay her cheek against the swell of his bicep.

"Shut up," she gruffs instead, shifting her weight and reaching around her partner to press the call button for the elevator. "It's weighted. For realism. I'm trying to get used to it."

"It suits you," he says, the words little more than shifting air and the work of his lips and tongue. Quiet enough that for a second, she wants to ignore them entirely.

Seeing her pregnant is doing things to him that she can't meet head on, doesn't dare turn her face towards, and Kate pushes the fingers of one hand into the pocket of her jeans and steps forward, grateful for the miraculous timing of the elevator. "It's weird. And uncomfortable."

"I'm sorry, Beckett," he says, for maybe the hundredth time since they got this assignment a little more than twenty four hours ago. She wishes he wouldn't gut himself like this, wouldn't draw a sharp line of self-deprecation down his middle to let his insides come tumbling out.

"It's not your fault, Castle. And - like I said yesterday - not the worst thing in the world. Not as bad as Vice."

He gives her a dramatic shudder for that, his whole body wiggling as he steps into the elevator after her and hauls her suitcase inside the car. "What was that like?"

"Undercover work?" she hums, drumming her fingers against the extended handle of her case so she doesn't rest her hand on the bump again. "Exciting. But-" ducking her chin, she wonders how much of this he really ought to be hearing. Especially as her fake husband. The pretend father of her nonexistent child. "It always seemed to be freezing. And I was never. . .wearing a lot."

"At least you're bundled up now," he smiles at her, something boyish in it as if he's delighted with her. She's working hard not to be grumpy about this, not to snarl and snap at her partner's kindness. It's not his fault that she has to do this, not even his fault that he's enjoying it so much, and she doesn't want to see that awful twist of his mouth in disappointment with her.

Never again.

Out in the street, Castle tugs open the passenger door of his car for her, takes the coat she shucks and drapes it on top of his own across the back seat. Her cases go in the trunk next to his and then he comes back around, a frown puckering his forehead to see her still standing next to the car.

"Did you want to drive?"

"Hmm?" Kate shakes herself out of her reverie and realises she's stepped off the curb, her whole body orienting to keep her eyes on him, and now she's standing in the icy slush that gathers along the edge of the road. Grimacing, she slides as gracefully as she can manage into the passenger seat of her partner's car, a moment's hesitation grasping hold before she tucks her feet inside.

Her boots come up to her knees in buttery leather, and they'll survive the city's winter detritus just fine, but she doesn't want to get dirt in Castle's car.

"Oh," he says once he's in the car, pausing with his seatbelt drawn halfway across his body. He lets it go again and the buckle clatters against the metal frame of the door; Kate's nostrils flare in amusement and she fastens her own belt, alarmed at how much of it is necessary to cover her stomach.

At her side, her partner lifts his butt up out of the seat so he can wriggle his fingers down into the pocket of his pants, tugging them back out with a noise of triumph. "I almost forgot. You had to buy a whole new wardrobe, so I took charge of this part."

His fingers are closed in a fist around something and Kate shifts as much as her fake stomach will allow, bringing one knee up underneath herself so that she can turn and face her partner. "What part?"

"Rings," he beams, uncurling his hand to show her the little collection nestled in the cup of his palm. All three are platinum, two matching wedding bands and an engagement ring with an utterly obscene diamond, and Beckett sags back against the seat.

"You. . .bought real ones? I figured the precinct would give you something fake. Costume jewellery."

Colour bleeds into his cheeks and he turns his head away for a moment, his throat working as he swallows. She knew he was excited about going undercover, but this? "I want this to be at least somewhat enjoyable, for us. Or at least not terrible. And I didn't want either of us to have to wear some awful, plastic thing that would turn our finger green and give us away."

"I don't know if you can expense this, Castle," she says carefully, as if she's ever known him to be frugal before. As if that's the thing that has her hands clammy, makes her wipe them off against the material of her jeans.

"It's fine. I can just. . .return them. When it's over."

Turning back around to face forward again, Kate manages a nod and flicks her eyes to see him. Like this, she's only afforded a shard of his cheek, the regal slope of his nose. "As long as you're sure."

"I'm sure," he says, and then his fingers close around hers and he tugs her hand across the centre console, cradles it in his. Before she can pull out of his grip he's sliding them onto her finger, first the engagement ring and then the wedding band, and once they're nestled at the base of her finger he lifts her hand to his mouth and dusts a kiss to her knuckle.

His lips are warm, lingering against her skin and a shiver rips through her. Castle drops her hand as if he's been scalded and she takes it back, rests it awkwardly on top of her thigh. The weight of the rings is disconcerting, as if her fake stomach wasn't throwing her off enough already, but she can't help herself.

Fanning her fingers out, she admires the way the rings look nestled together, how the diamond seems somehow less obscene now that she's wearing it. All over again, it hits her that he chose these. He went to a store - probably more than one - and agonised over it, hands in his pockets and affable noises of dismissal aimed at the swarming salesgirls.

Castle starts the engine and eases the car smoothly into the flow of traffic, both hands cradling the steering wheel, and Kate huffs, shifting her hips in the seat to get somewhere close to comfortable. She hasn't been able to work up to this gradually, hasn't marvelled over the growth of her bump, and the suddenness of the extra weight and girth is throwing her off entirely.

To distract herself from the awkward fit of her body in the car, Beckett flicks her eyes towards her partner, the wedding band that circles his own finger. "You didn't let me do yours."

"Do what?" he asks, gaze never moving away from the windshield. This is the first time he's ever been the one to drive and Kate lets two fingers rest against her mouth, tracing the arc of her amusement.

He's so serious, a little frown puckering between his eyebrows that makes him seem almost grumpy with the responsibility. Kate settles her other hand the only place that's comfortable, resting against the curve of her stomach, and then she understands.

Precious cargo.

They have to sell the charade if this undercover operation is going to be a success, and that means convincing everybody that they really are having a baby. And so the protective side of Castle, the father in him, rears its head to keep safe their imaginary child.

"You didn't let me put your ring on."

"I didn't think you would want to," he says, turning his head to see her for a moment. They're at a stoplight, the car humming as it warms up, and Kate wriggles in her chair again. It's probably for the best that her partner is at the wheel; she can't even figure out how to sit properly, never mind focus on driving. "There's a cushion for you in the back."

Twisting against the confines of the seatbelt, Kate turns to look into the back of the car and sure enough, one of the pillows from his couch in the loft is there waiting. She stretches an arm, shoulder pressed against the back of her seat so that she can reach, and a huff of triumph escapes her as she hooks her fingers at one corner, where the stuffing doesn't quite pad out the cover.

Beckett tugs it through the middle of the car and shifts forward in her seat, nudges the cushion in at the small of her back. Leaning against it, the relief is immediate and she groans, eyes closing as tension swells and then releases all along her spine. "How did you know I'd need that?"

"I've done this before. With Meredith, I mean. And I know it's not real, and you're not actually pregnant, but I figured some of the discomfort would be the same."

"Thank you, Castle," she offers, dipping her chin before she remembers that her hair is caught in a knot at the nape of her neck and only a few strands slip forward to hide the flush of gratitude. "And about the ring-"

The light switches to green and her partner accelerates smoothly, easing the sedan along in the flow of traffic that winds along the riverbeds of the city. His hands cradle the wheel, the leather sliding through the curve of his palm when he makes a turn and Kate settles back against the headrest, keeps her eyes firmly facing forward.

"We can drop it," he says like an olive branch, but she won't take it. Instead, Kate rolls her head to the side and smiles at the side of his face, catches the quirk in the corner of his mouth as if he's helpless but to echo her tentative amusement.

"I don't want to drop it. I wanted to-" Beckett pauses, swallows back the ridiculous flood of grief that swamps her. "I wish I could have returned the favour."

That makes him huff a breath of almost-laughter, but Kate turns to look out of her window, let him not see the petulant scowl that swells in her bottom lip, knots her forehead. The thing about going from partners who sometimes touch but never talk just yesterday, to here in this suburban car with matching rings and a baby on the way, is that they didn't get the journey.

She never got to wake up next to him for the first time - she is ignoring that tiger incident entirely - and stare at the breadth of his shoulders, scoot closer and closer along his insane thread count sheets towards the warmth that rolls off his bare skin. Touch kisses to the tender place just inside of his bicep until he came awake and rolled to see her, that lopsided grin breaking his face wide open.

"Have you thought up a backstory?" she asks him and he starts, clearly expecting the silence to linger. After it swelled in the car, made his fingers drum against the steering wheel in agonising discomfort, he fiddled with something in the electronic display of the dashboard and then it connected to his phone and a playlist started.

They've gone through handfuls of songs now, and he must have thought she wasn't up for conversation because he kept inching the volume higher and higher as if to drown out the awful static of their quiet, enough that he has to turn it back down again now so that he can answer.

"Sort of? I figured we should stick close to what we know, career wise. So I thought maybe I'd teach college literature, and you'd be a lawyer."

"What if they google us?" Kate says, panic suddenly clutching hard at her so that she rears against her seatbelt, the need to get more upright thrown off by the counterweight of her stomach. "Castle, you're famous. What if they recognise you?"

He winces at her, something boyish in the scrunch of his face that makes her heart roll over, close enough to how she imagines the flutter of life in her belly would be that a soundless gasp escapes her and a hand migrates to rest on top of her stomach again.

"I guess we just have to hope that nobody recognises me. We've got fake IDs, and tech said they'd generate some fake web hits for our aliases. I. . .kinda already told them what our covers were," he gulps, turns his head for half a second to see her. "I hope you're okay with being a lawyer."

Groaning, Kate presses the heels of her hands into her eye sockets until she sees the pop of vibrant colour, kaleidoscopic green. "Castle, this place is going to be full of bored, sexually frustrated housewives. Isn't that ninety percent of your fanbase?"

"Hey," he grumps, a flash of real hurt transforming his face for just a moment, and before she knows she's doing it Kate reaches out to skim her fingers along the puckered cuff of his sweater where it's pushed up to his elbow, flirting with the skin at the inside of his arm until he shivers.

"I'm sorry. That was cruel. And not true. But even so, are you sure it's not going to be a problem?"

"No," a huff of nervous laughter escapes him and Kate realises her hand is still resting at his arm, draws it back. "I'm not sure at all. I guess we'll just have to hope for the best."

Burying her face in her hands again, Kate moans in not-quite-false despair. "Oh, god. We're not going to make it five minutes."

"It'll be fine," her partner says, but his voice cracks a little at the end and he flushes, shifting in his seat. Pity makes her turn her gaze away from him, lets him escape her accidental scrutiny, and Kate picks at the edge of her still-snaggly nail.

She meant to do something about that, absolutely sure that it'll mess up her suburban housewife exterior. Maybe even go against the codes of conduct that she's quite sure the gated community will impose, and she reaches for her purse from the footwell, rummages inside in search of a nail file.

One scrape along the ragged edge and her partner yelps, his spine snapping straight and one hand peeling away from the steering wheel to swat blindly at her. "Please, please, don't do that in front of me."

"File my nails?"

"Yes," he shudders. "I hate the noise. It makes my teeth hurt."

"Oh-kay," Kate says slowly, dropping the nail file back into her purse and setting it down at her feet again, leaning back against the pillow. Her hips are aching after such a long time in the car and she reaches a hand behind herself to massage the muscles that flare in her pelvis, struck for a moment by the ridiculous yearning to stretch out someplace soft and let her partner's warm hands do the work. "Are we almost there?"

Castle turns a smile towards her for that and it makes her feel childish, squirming under his amusement. "Another half hour. We should use the time to air our grievances, before we have to pretend to be married. Wanna yell at me?"

"No, I don't want to yell at you," she laughs, but the lift of his eyebrow in self-deprecation brings her clattering back down into dismay and she brings a knee up onto the seat, twisting around until her stomach is comfortably arranged and she can see him. "You've been really great about this whole thing. I expected more teasing."

"I figured that could wait until it's over with," he smirks, slamming his shoulder back against the seat in an effort to escape when she reaches out to swat at him. The smile slides down his face like the smear of half-removed costume makeup when he catches sight of her frown and he reaches for her hand, tucks her slender fingers up against his palm and squeezes. "I'm not looking to make you miserable here, Beckett. I'll be a good husband, if that's what you're worried about."

"I know you will," she admits, because even with Gina, even with Meredith, she knows her partner. How he loves to love, yearns to take care of the people that matter to him, and although she's sure he must have had his failings in his two previous - crap, his only - marriages, she knows he'll pour everything of himself into caring for her.

Especially with the baby.

Kate saw the light that flooded his face when the captain told him what this case would involve, the cascading joy when she opened her door to him earlier, and she knows he's fallen hard for the idea of their child. It's sweet, and also entirely too much for her to deal with.

If she finds he's bought anything, even so much as a knitted cap, for their non-existant little one, she will kill him.

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