A/N: This may be a little OOC, but I tried my best. It is, after all, a fun little AU story for entertainment purposes only. No copyright infringement intended, and no hurting of anybody's feelings either.
Warning: This is going to be naughty and dirty and all kinds of wickedly good. If that's not your cup of tea, turn away now.
(If you're enjoying it, please leave a review so I can feel like I actually accomplished something and haven't spent hours upon hours doing something "unimportant" while I could have been working on "important" stuff... I would really appreciate it.)
Thank you to Marie for quickly reading through this for me and just generally being awesome and smart and funny.
When Serena Kaye shows up at their crime scene in a luxurious tight-fitting blue dress, hair done up in a fancy bun accentuating her cheekbones, throwing around know-it-all answers while the New York police is trying to go about their jobs, Detective Kate Beckett is less than amused.
When Rick suggests to her that the art insurance investigator might be useful for their case, clearly impressed by her physique and manner and complimenting her "valuable assets", mild annoyance turns into instant dislike.
He's quick to throw in "not those kind", but she already saw him ogling.
(They've been in a relationship for almost a year now – there's not really anything he can hide from her anymore.)
She grudgingly has to agree that the woman's theory may have some possible truth to it, and calls Ryan to check on the loading bay vans just like Serena told them to.
A couple of hours later her annoyance level spikes when the theory turns out to be right on all counts and Castle's smile turns smug.
She's thoroughly pissed when she gets called into Gates' office and sees the blonde sitting there, smiling confidently.
(To say that they start out on bad terms would be an understatement.)
That's why Kate is especially taken aback when the woman's low and sultry "Hello again" sparks something other than anger in her. Entirely unexpected, she stutters, her heart missing a beat at the sudden overwhelming surge low in her belly.
"Miss Kaye has presented me with a very compelling proposal" Gates says as she closes the office door, and Kate can't help but think of a couple of compelling proposals as well…
Rick and her have never tried a threesome, but the possibility of it has been discussed – several times and with astonishingly little alcohol consumption involved.
(After Castle had found out that the hardnosed detective had been in a year-long relationship with a red-haired prima ballerina during her first year of college, discussing exciting additions to their already thrilling sex life had merely been a natural progression of dinner table topics.)
She snaps back to the present to fight the Captain's decision, but it's only half-hearted; more for show than anything else. Still, Kate is surprised at her own ability to form grammatically correct sentences when her brain is clearly otherwise occupied.
"Sir, I prefer working with my team" she insists, but Gates has a quick throwback at the ready. "Which includes a consultant with no expertise at anything?" she questions, and Kate has her mouth open to assure her that, oh you have no idea, dear Captain, but he has stunning expertise in all the important matters, but thankfully she catches herself at the last second.
She's rendered speechless when the gorgeous (so fucking gorgeous – no wonder Castle was ogling her!) woman reaches out.
"I look forward to working with you" Serena says and shakes her hand and Kate can barely offer a tight-lipped smile, because their skin is touching and goose bumps are racing from her hand down to her toes and she doesn't want to embarrass herself in front of her boss so she nods curtly.
(She hates that her body is reacting even when her mind is still trying to convince her that this person is to be disliked. It makes her a little angry; mostly at herself for being so weak, and at the beauty in front of her for being ballsy enough to come back, to stand up to Captain Iron Gates and charm her way into the precinct.)
She's grimacing when she has to admit Serena was right, that there's supporting evidence for her theory. Her coffee suddenly tastes like defeat.
She looks over to Rick and Detective Ryan and they're scurrying to look away, pretending they haven't been watching them the entire time.
She lets them stare. She can imagine that they must be quite an attractive sight, the two of them together – the slim blonde in her feminine top and her rounded curves, and her own tall figure, clad in a rather gentlemanly outfit today (Oh, what a coincidence!).
"This is the best way for both of us to get what we want" Serena offers and Kate can barely stop the deep blush from spreading to her cheeks and giving her away.
(If only Serena knew what Kate wants right now…)
"Think of it as a merger" the blonde adds.
"More like a hostile takeover" the brunette mutters, then realizes what she just said and quickly turns away.
"Umm…I'll have Detective Ryan bring you up to speed" she chokes out and struts away, before she can say anything else equally stupid.
Richard Castle has always been an admirer of smart, sophisticated, quick-witted women. He does appreciate it when they're sexy-as-hell, drop-dead-gorgeous, too.
Art insurance investigator Serena Kaye definitely has some valuable assets to offer, in all the different meanings of the phrase.
When she shows up at the museum crime scene, he practically pleads in front of Kate to take the help that Serena offers. And even though he really wants to keep pushing, he stops when his first try gets shot down – there's a 90% chance that the annoyed look on Kate's face is fuelled by jealousy. It simultaneously flatters him, turns him on, and scares him a little bit.
(He knows from experience; one wrongly worded sentence and he'll sleep on the couch tonight.)
He's not a cheater. His heart belongs to Kate and he would never cross any lines with another woman unless Kate specifically allows him to (It's always been one of his top 10 fantasies for them, but if the way his girlfriend is glaring at the blonde is any indication, that's not going to happen anytime soon…) but that doesn't mean he can't use her for inspiration, can't observe her and turn her into a character for his next series of books; maybe as a new arch nemesis for Nikki?
So in other words, he's delighted when Gates forces Kate to partner up with the insurance investigator on this case. He gets caught staring at them from afar, fears for his well-being for half a minute, but can't really help it. He knows it's all over his face as he smiles at the woman over their briefing at the precinct.
Serena smiles back and then steals a glance at Kate, looking her up and down as if she's…no, that can't be. Is she checking her out? His heart thunders in his chest at the thought, but he tries to keep his focus on the case because Ryan keeps looking at him like he's supposed to share his insights. He saves himself well enough; Ryan is answering his question as if he knows what he's talking about, giving Rick a couple of seconds to catch himself, collect his scattered thoughts.
When Esposito walks in and stares unabashedly at Serena, he introduces her as "she's with us", hoping that his girlfriend won't rip his head off.
(After all, he didn't say "she's with me", so that's got to count for something…)
Kate glares at him, her mouth a tight annoyed line, but it's not as scary as it could be; she's not giving him her full-on death stare.
Basically that's the only reason why he's taking his chances and leaving with Serena when she says that she can't take cops with her – he wouldn't dare follow the blonde if Kate's threat had been a little firmer, a little more lethal and absolute.
"Where are you going?" she asks him though, and his heart leaps in his throat.
"Umm…I'm not a cop either" he says and tries to ask for permission with his eyes, their entire conversation nonverbal, like so often.
"Fine" she says with an angry hint in her voice, allowing him to start the game, but warning him to take it slowly.
(Maybe his fantasy is within reasonable distance after all.)
"You're an interesting man, Mr. Castle; crime fighter by day, writer by night." Serena murmurs to him when they're sitting in a dark bar, in that throaty voice that has his insides turned upside down and humming even though he tries to fight it.
He swallows and smiles. "You're pretty interesting yourself" he responds, trying to gauge her reaction to see how far he can push. He doesn't give her time to answer though; just casually planting the compliment and continuing straight away with the case at hand.
"So…we're meeting a secret informant?"
Serena hums appreciatively and sets down her drink to look at him, really look at him. "Guess Beckett doesn't just keep you around for your good looks…" she flirts (because really, it's nothing less than openly flirting with him) and he smiles a little wider, knowing that the groundwork is already laid, knowing she's interested in him and he can start pushing.
The informant interrupts them before he can make his move, but it's okay – she's pushing an envelope full of money across the table like a sly supercool character from one of his books and it's just so hot that he's not able to form any coherent let alone charming sentences anyway.
He does, however, open his mouth once they're back at the precinct and the rest of the team is nowhere to be seen – probably doing their job in one of the interrogation rooms.
"It seems like you know a lot of people" he tells her, appreciation lighting up his eyes, the corners of his mouth lifting upwards.
"I've been around" she confirms, stepping a little too close for a stranger, her luscious and sweet-smelling body just an arm's length away, Kate's desk at her back.
"I've seen things" she murmurs, reaching out with her fingertips, just barely brushing his shirt front. "I've done things" she taunts him, her pink tongue peeking out between her beautifully curved lips, attracting his attention.
He hums, low in his throat, his body vibrating. He needs to talk to Kate, as soon as possible. He doesn't want to pursue this if he's not allowed to follow through. He doesn't want to flirt with Serena and face the angry wrath of Scorned Beckett when she decides not to join in.
Rick Castle is not one to turn away though when a sexy and savvy woman like Serena slides closer still, her hands finding his bicep, his broad chest.
"What are you doing later tonight?" she whispers, and it's bold and direct and his eyes sparkle because she's so confident and hot and he'd really like to touch her, his hands twitching at his sides as hers slip under his coat and spread across his ribs.
"I…umm…"
She jumps away from him at the sound of footsteps and he clears his throat, straightens up his jacket. He turns around to see his girlfriend approaching, looking confidant, sexy, pissed and jealous all at once.
Thankfully they have actual substantial information to talk about, so Serena quickly distracts them with the case, Beckett's face falling back into cop mode.
"I'll work some of my other sources, see if we can get a line on him" Serena announces, finding that she's really starting to like working with the police.
(Both Rick and Kate have something inherently sexy about them that goes deeper than just their physical appearance. It's as if their minds are sharp, fast-witted and just a little wicked.)
"Oh, another jaunt into Manhattan's seedy underbelly? Cut me in!" Rick exclaims enthusiastically, but she catches Kate's glare behind his back and decides that she'd rather not interfere with whatever is going on between those two until they've figured out what's allowed and what isn't.
"Sorry" she turns him down, putting on a fake smile because really, she'd rather have her wicked way with him in the next storage closet than push him away right now. "I'll just be making phone calls, boring stuff."
The pretty detective looks relieved, giving the insurance investigator a short nod to say that she appreciates the move. (Serena wouldn't say no to dragging her into a storage closet either…)
"I'll catch you later?" she asks, even as she's turning away and glancing around for her purse.
"Catch me anytime" Rick grins and she can feel his eyes burn into her backside all the way until she disappears around the corner.
When Rick finally turns around, Kate is gone, her heels clicking on the wooden floor just around the corner in front of him. He hurries to catch up to her and finds her already walking into the elevator, ready to head home.
(Their home, ever since she moved in three months ago when his mother's acting school had thrown off enough profits for her to afford her own place.)
She doesn't acknowledge him until the doors are closing behind them and then she presses the button that's holding the elevator in place and yanks his body into hers, tumbling together, their lips crashing and molding and nipping.
She takes him, takes from him without asking, knowing she doesn't need to. She gives back too, offers her hot mouth to him, gives him a low moan and a slide of her tongue against his, her nails scratching at his neck.
And then she's gone, ripping herself away from him to shove at his chest, flushed and panting and a fire burning in her eyes.
"You were staring at her" she growls and it's not a question but a statement. He's not sure he hears criticism in her voice, so he dives in blindly.
"She's hot" he admits and then gulps, preparing to be punched or poked or snarled at.
"She is" Kate agrees instead and they stare into each other's eyes, neither of them backing down.
(Everything they cannot say is written all over their faces, in their darkened pupils, their swollen lips. He's dumbstruck by it, rendered speechless, and she takes the opportunity to make a decision for both of them – or rather, all three of them.)
Kate pulls Rick back to her, her teeth rough against his jaw, nipping their way up his cheek towards his ear.
"Do you want me?" she murmurs and he trembles, his knees so weak that he has to dig his fingers into her hips to stay upright.
"Yes" he groans, his thigh pressing between her legs, his fingers slipping beneath her shirt because he doesn't want to be the only one trembling.
"Do you want her?" she whispers, licking at his earlobe and the sensitive spot just behind it.
"Not as much" he presses out, because it's the truth.
(He could never want anyone, love anyone the way he wants and loves her.)
But-
"You both. Together. I want-"
He gasps as she grinds against him.
"Yes-"
"-Together."
She finds his mouth again, softer now, sweet and wet and loving.
"I love you" she speaks against his lips and he kisses her once more, his tongue sweeping across the corner of her mouth as he diverts to the side, suckling his way down her chin, her long and tender neck.
"Only you, Kate."
His arms encircle her fully, his warmth radiating through her entire body.
"Only you."
