A/N: So... I'm aware it's been quite some time, and I'm also aware that this is not the promised sequel to "A Death in the Family". The sequel is still very much part of my plans, though, I promise. In the meantime, here's a summer-themed, fluffy one-shot. Takes place sometime in the future. And I have Carolina17 and Whatarushh to thank, for giving me feedback on this and telling me it was worth posting. Hope you'll enjoy it!

Disclaimer: Let me check - nope, still not mine.

It's midsummer in the Hamptons; the July vacationers have left and the August ones haven't gotten there yet, making for a lull in the beach traffic. Of course, it still leaves the rich, idle people like Castle who have nothing to do but gaze at the sea and throw parties all summer, but the beach is as close to empty as Kate has ever seen it. It's the only reason she's managed to drag Rick down here, to the public area; otherwise, the spoiled little boy that he is refuses to go anywhere but to his own swimming pool and private stretch of sand.

And while Kate is usually so reserved and mindful of her own privacy, she found that occasionally, she likes to be surrounded with people (it has nothing to do with her being uncomfortable with spectacular display of Rick's money, no, nothing at all).

The dark-haired woman shifts, easing the tension in her shoulders that comes from maintaining the same position for the last twenty minutes. Her long legs are exposed to the sunlight, while the parasol shelters her upper half. The light breeze keeps messing with her hair, and Kate runs a hand in her dark curls in an unsuccessful attempt to tame them. Closing her book for a moment (she's two chapters away from the end, but she keeps getting distracted), she looks around and quickly finds them.

Alexis, her long red hair in a braid, is trying to sink her dad, but it seems to Kate like she disappears in the waves more often than Rick does. Castle looks like a kid, his eyes shining brightly – didn't he have sunglasses on earlier? – the corners of his mouth turned upwards in a joyful smile. He has missed his daughter; the detective knows it, even if he seldom speaks of it. The writer laughs, and the sound travels to where Kate is lying down, warms her heart like the afternoon sun is warming her skin. Her eyes linger on his broad chest with satisfaction: since the beginning of the summer, she's been using some of her darkest tricks to get him to run with her. She's succeeded quite a few times, and now she gets to enjoy the fruits of her labour. Not that Castle really needs her help, though. He's always been pretty easy on the eyes. And it's not why she loves him.

All thoughts of her book forgotten now, the detective leans back on her elbows, watches as Alexis climbs her father's back with uncanny agility, only to end up underwater when Castle decides to perform his own, literal version of "The Yellow Submarine".

Well, it's not yellow so much as brown. He's gotten quite a tan; his skin is almost dark enough to make Kate jealous (or it would be, if she didn't get to run her fingers across it whenever she wants to). No matter what they say, solving murders in NYC doesn't work so well for your tan as pretending to write in the Hamptons does.

Okay, maybe not "pretending". She hopes not, for Nikki's sake. For her own. A delicious thrill runs through her at the idea of a new Castle novel, and she couldn't deny how impatient she is even if she wanted to. Which she doesn't, really. But Kate's not one to ruin the pleasure by taking an early peek, and so she's waiting until Rick deems it good enough for her to read, until he finally gives her the final manuscript. They've got an agreement: he's allowed to ask her questions for the novel, as long as they're not too specific. She doesn't want his questions to lead her into getting a false picture of the next novel. He still gets most of his raw material from the cases, anyway, even though he's not at the precinct as often as he used to.

The precinct. Kate suddenly wonders how the guys are doing without her, if they've thought of asking the best friend whether she had any idea… Then she catches herself and can't help a smile. She's a little hopeless, isn't she?

And yet she's told herself to leave Detective Beckett in New York, to leave her tough exterior and her case behind (and it's not her case, she corrects mentally, it's Ryan and Esposito's) so she gets to be Kate Castle for those three days of escape to the Hamptons. Kate Castle.

The name is still unfamiliar, foreign – but pleasantly so. She's kept her name at work, because it's simpler this way (and the truth is, she kind of likes her name, even though Castle's is nice as well). Rick has told her a dozen times that he didn't mind, and she's finally come around to believing him.

Journalists call her Mrs. Castle, sometimes; and when she went to her last doctor's appointment, it was "Mrs. Castle" they called for in the waiting room.

It always takes her a dazed second to realize she's the one they're talking to. It all seems like such a dream sometimes. Not that Castle hasn't gone to every possible length to make her involved, to make sure she wouldn't run – they planned the wedding (as small as she could get away with) together, picked flowers arrangement during her lunch break, tasted cake samples after they closed a case, and argued over locations in between theory-building moments. Rick set up visits to bridal stores for her with Lanie and Alexis and Martha, surprising her by not showing up. He had this stunned look written almost permanently on his face at the time, like he couldn't quite convince himself she had said yes. That it was real. But it vanished at last, when she looked him straight in the eye and said, "I do," proud that her voice didn't waver in the slightest.

Kate smiles, unconsciously twirling a dark strand of hair around her index finger. She found her engagement ring in a fortune cookie. A fortune cookie, one night that she had to work late, and Rick had surprised her by showing up at her apartment around eleven, waving boxes of Chinese at her like they were the magical pass to her apartment (and who is she kidding, they were).

She still hasn't found out whether he asked the restaurant to make a special cookie for his order, or if he just cooked it itself and put it with the rest of the fortunes. It looked inconspicuous enough, and she had had absolutely no idea what she was going to stumble upon when she had cracked it open.

In hindsight, maybe she should have seen it coming. Things had gone so well between them those first six months, and it was exactly like Castle to get carried away and run to the first jewelry store when they hadn't even moved in together yet. Not officially, anyway.

And the sneaky little bastard had to go and chose the most gorgeous engagement ring on the planet, too. A simple, incredibly thin golden band with a tiny diamond in the center, refined, subtle. Beautiful. Kate had had to refrain from immediately sliding it onto her finger. A small part of her had wondered at Castle being able to choose something that was so far from shiny and showy.

She remembers the shock and awe, remembers looking up at him with an arched eyebrow, her heart in her throat. And then –

Then everything got out of hand without her knowing how. Rick met her gaze, somewhere between scared to death and deadly serious (all very fitting expressions considering the way they had met), and he said with false detachment, "I told you before. I'm never letting you go."

It was the right thing to say, taking the drama out of it, making his proposal sound like another one of his "Always". Kate looked down at the ring again, smiled at the way her heartbeat had settled before the first terrified peak. She wasn't so scared anymore. Her concerns about the press, about Castle losing interest had been overruled by how wonderful it felt to wake up next to him every morning, to find his blue eyes smiling at her; overruled by the way their shoulders brushed when they took the time to cook together, by the way he hold her hand when they walked in a park, loose enough that she'd have the possibility to draw back, if she needed to. She didn't need to. She didn't want to let go either.

So that was it, then. That was what life with Richard Castle would be like. What life with someone who knew her, loved her – all of her – would be like. Well, she was in.

"Okay," she said slowly, finding his blue orbs with hers, letting a half-smile curve her lips and not caring one bit if this was the most unorthodox dialogue in the history of marriage proposals. She saw him gulp, saw the hesitant happiness flicker in his eyes.

"Okay?" He repeated, unable to help his disbelief from showing in his voice.

He looked absolutely adorable, torn between the joy that wanted to burst through him and the fear that he hadn't understood her, and it only cemented Beckett's decision. She wanted to see the pleasure in his eyes when she smiled at him, kissed him, teased him; she wanted to laugh at his jokes, make him laugh in turn – and more than anything, she never wanted to give him cause to doubt her again.

"You want a proper answer, Rick? You ask the proper question."

And suddenly it was right there on his face; the unmitigated, cloudless delight, the bright light of summer days. The smile that crinkled his eyes.

He leaned in, crowding her, his arms on both sides of her, his mouth at her ear. It distracted her, the warmth of his shallow breaths against her skin, the proximity of his broad chest; it made her lose her footing. Of course, it was exactly what Castle was going for – to leave her defenceless against his next attack.

"Marry me, Kate."

She wanted to be defenceless, she found. She wanted not to remember the reasons she had to say 'no', the logical arguments and serious questions she ought to be considering. She just wanted this – his lips brushing against her neck, his solid, reassuring presence.

"Yes, Castle," she said, surprising herself with the steadiness of her voice; and it was almost painful, how her chest seemed to burst open under the pressure of her love, her heart no longer able to contain it. "I'll marry you."

Kate blinks against the unexpected wave of emotion that courses through her at the memory. Castle hasn't given her cause to regret her decision; if anything, she fears sometimes that her own difficulty to share, to open up, will drive him away. But Rick doesn't show any inclination to leave, and he has his own tricks, his secret ways to get to her heart. They work more often than not; Kate can remember a couple times when she found herself talking about her mom, about her childhood, without having any idea how she got there.

Of course, they've had darker days. They've fought, hard, about silly, unimportant things – and sometimes about things that mattered. God, they've said terrible things to each other. But she doesn't want to think about it today. Not when the sun is shining bright, not when she's managed to push the still-unsolved case of her mother's murder at the back of her mind.

If there's something she's learned with Castle, it's how to enjoy a good day. And she'll fight to preserve that little bit of peace, of light, that means so much to her.

In the water, Alexis seems to have given up on sinking her father; the dark-haired detective sees her swimming away, while Castle shakes himself like a dog (an attractive one, she'll give him that) before making his way up to her.

Kate's heart misses a beat or two as she watches him jog towards her, the man she loves, droplets of water catching the sunlight on his body. He's not the firefighters' calendar type, and it's just as well. He's hers.

She quickly puts her book away, and a couple of seconds later she's glad that she has, because Rick finds it highly amusing to drop on his knees and give her a wet hug. She fights perfunctorily, cries out because the water is cold, and finally gives up, laughing against his chest.

He kisses her, a mixture of cold lips and warm tongue, and Kate shivers, moaning softly into his mouth. She draws closer, hands sliding at the back of his neck, tasting salt on his tongue. Castle's arms tighten around her, and he nibbles tenderly at her bottom lip before letting her go. The way he looks at her – oh, God.

He's her husband, and she should probably be used to it by now. Only, it doesn't work like that.

Her cheeks feel like they're flaming, and Kate raises a hand to her face, her fingertips brushing self-consciously against her skin. Rick's hand comes up, gently cupping her other cheek.

"So beautiful," he says reverently, brushing his thumb against her cheekbone.

She turns her head, keeping her eyes on his, and kisses his palm. Then she flicks the tip of her tongue against it, and Castle closes his eyes briefly. Gratitude threatens to swallow Kate whole, makes her heart swell – hell, she'd be willing to hug Jerry Tyson, just for letting Rick live in that motel room, whatever his reason was. And maybe it's terrible of her, to be grateful towards a runaway serial killer, but this – this thing they have – it's everything. It's everything to her. And she shivers to think of all the things that could have made it never happen.

Shivers to think of the Toms and Ginas and Joshs, of the bombs and gunshots and freezers – and worse than that, of the misunderstandings between them.

That summer she spent without him… But he came back, he came back, and suddenly there's nothing more important than to tell him how much it all means. Kate cradles his face in her hands, brushes her lips against his.

"Thank you," she whispers, trying to say it all through her eyes, her love a fierce, ferocious thing inside her.

He's about to ask for what, she can see, but then Rick's parted lips turn into a smile as understanding slowly dawns on him. For coming back, and being there, and not giving up on me. For loving me.

He leans in and wraps her into the most intense hug she's ever experienced, pouring his own love, his own need for her into his touch.

"Right back at ya," he murmurs in her ear, before dropping a kiss there.

It tickles, and Kate laughs soundlessly. Castle takes that as agreement and his lips start drawing patterns on the side of her neck. Surprised, though not unhappy, his wife gasps, and the sound turns into one of approval, soft and uncontrolled, as he makes his way down.

"Mrs. Castle," he says, amusement lacing with mock disapproval in his tone, "this is a public beach. You can't make sinful noises like that."

She narrows her eyes at him in response. He is the one who started the whole thing.

"Come on," he says, finally releasing his hold on her. "Come swim with me."

"You seem very eager to go back to the water for someone who just came out of it," Kate points out innocently.

"Yeah? Well, maybe you shall tell that to the person who's responsible for my, how shall we put it? My getting a little flustered over here."

A chuckle escapes her as she takes his hand and lets him help her to her feet. Her bikini is black, and rather demure, but it certainly clings to her form in an attractive way. He cannot help staring – not that he's trying very hard.

"Like what you see, Rick?" She asks with a provoking light in her eye.

She draws closer, her hands coming up to rest lightly on his chest.

"Like is an understatement," he replies, his voice a little rough.

"A euphemism?" She suggests with a sexy half-smile.

He groans. "You've got not right to be this hot."

His eyelids drift shut when her lips brush against his, but she doesn't linger. Instead, she works her way up to his ear, and Kate knows he expects something completely different from the words she half-whispers to him.

"First one to reach the water wins, Castle."

And then she pushes him back, not really caring that it's cheating, and she starts to run.

The writer follows her with a dazed look, watching for a moment the play of those long legs, of the taunt muscles under the smooth skin, before he remembers to chase after her.

Alexis reaches the yellow buoy and allows herself a minute to rest. Ever since she started going to school, when she was but a little girl, she's always favoured team sports. They're so much fun, and she enjoys the fact that everybody has got to play together for it to work. The way it feels when good teamwork brings you the victory - there's nothing like it.

And yet, swimming has remained her only exception to that rule.

There's something special about feeling your body held up by the water, the weightlessness, the quietness of it all. When she swims, the red-haired girl feels she only has to focus on her breathing, every other concern easing away from her mind. She no longer worries about that sociology exam she thinks she failed, no longer wonders why Ashley hasn't been returning her calls lately, no longer has to ignore the sad look at the back of her father's eyes that speaks of how much he hates the distance between New York City and Stanford.

She just is.

The air burning its way into her body with every breath, the tightness in her muscles, the contrast between the coolness of the water and her cheeks warm from the exercise – it grounds her, ties her down to the earth, if that even makes sense.

Floating on her back, Alexis lets her eyes roam over the blue expanse of sky above her, only disrupted by a few white clouds here and there. It's so peaceful. She breathes in and out, slowly, suddenly glad to be where she is. She had doubts about coming to the Hamptons, other plans that some friends of hers made and were eager for her to take part in, but it's all forgotten now.

She slowly turns, and starts swimming back towards the beach. She has barely covered twenty feet when she stops, realizing that the couple that is now running to the water is no other than her father and Kate. A smile touches her lips, and she pauses to look at them. The dark-haired, slender detective is the first to crash into the waves, but Castle isn't far behind; and when Kate emerges he lunges at her, causing her first to cry out, then to burst out laughing.

Alexis knows how much her father loves Kate's laugh (it isn't hard to figure out from the way he stares at his wife, in awe, whenever she lets evidence of her humour roll free) and she has to admit that she rather likes it too. It's a beautiful sound, carefree and untamed.

She isn't oblivious to the fact that the detective does a lot more laughing whenever her dad's around. Part of her is grateful – unbelievably grateful – that they've found each other at last, because she knows it's made it so much easier on her father to accept her leaving.

Another part of her feels guilty for feeling that way.

But regardless of her own relationship with Richard Castle, watching the couple interact, watching their eyes sparkle with happiness whenever they're in close proximity with each other, is source of endless joy to the young woman.

Alexis had to read Jane Austen's Emma for one of her courses last semester, and there's this sentence that stuck with her for a while. "It is such a happiness when good people get together – and they always do."

The line, while somewhat hidden in the middle of one of Miss Bates's speeches (one of the most chatty characters Castle's daughter has ever encountered in all of her readings), struck her forcibly because, while she agrees with the first part of the sentence, she knows, by experience, the second half to be wrong.

Good people don't always get together. In Alexis's experience, good people can run in circles around each other for years, and never find their way to the other. Good people, no matter how good they are, can be pretty damn stubborn; complete idiots even. Good people can be scared, and sometimes they let their fears govern them.

And that knowledge makes her all the more appreciative of the scene playing out in front of her eyes. Somehow, her dad has managed to scoop Kate into his arms – she's not putting up much of a fight, because she's laughing so hard – and he seems to be threatening to drop her in the water. While Alexis can't make out exactly what they're saying, the sounds of their voices merge together harmoniously, and sometimes a broken sentence reaches the young Castle. By the time she hears the detective's threats towards her father's manhood (she winces a little, half in sympathy, half in distaste), she's grinning and headed in their direction.

Those two make it hard to stay away.

As she gets closer, the redhead catches sight of the wide grin that splits Castle's face in two, and realizes once again that she's never, ever, seen him that happy with another woman. If she didn't love her father so much, she might be jealous; but that's not who Alexis is. And she swims more vigorously, attracted to the bubble of light Kate Beckett and Richard Castle seem to create together.

Of course, the young woman is old enough to know that no relationship is perfect. She's heard them fight sometimes, albeit through closed doors; and she's not a little girl anymore. She stopped believing in Prince Charming and all that stuff long ago. (Well, okay, maybe not that long ago).

She realizes that romantic comedies only show some, but not all, of a relationship's aspects. But watching her dad and Kate together…

She can feel it burning inside her, stronger, brighter – the hope that there's someone out there who will be right for her, the way Kate and her father are right for each other. Maybe it'll turn out to be Ashley, or maybe someone else; she can wait, knowing that this kind of thing is possible, having the tangible proof of it right in front of her.

But it doesn't matter right now. What matters is that she get to Kate, and tag-team with her against her dad.

This whole thing is starting to feel awfully like family, she thinks suddenly, the idea tugging gently at her heart.

Not that Alexis minds. She's always wanted a little brother or sister, anyway.