A/N: This is a sequel of sorts to In the Name of Research, though you don't really have to read that first to enjoy this, it'll just give it some context. This also probably won't be the last one of these I write, so. LOOK FORWARD TO THAT IF YOU LIKE THIS KIND OF THING. And please don't read this if you don't like this kind of thing, because I really did not chicken out on the threesome part this time. Natalie is ALL UP IN THERE. Okay. And special thanks to djjazzyflax because without her this would not exist.

Kate Beckett has had her fair share of brushes with celebrity since a certain best selling mystery writer declared himself her own personal shadow four years ago. Book launch parties, feature films, popular actresses wanting to pick her brain and watch her every move.

Literally her every move.

Like that night Natalie Rhodes' "research" ended up with the three of them sprawled across Beckett's bed in a haze of post coital bliss and tequila, like the handful other nights since.

Because when Natalie Rhodes comes to New York City, she doesn't stay at a hotel, she stays with them.

It's not the first time, and it's not the last time, this time, as Castle leaves red finger marks against Beckett's bare hips, trying to hold her down and against him in his lap. He's back flush to her headboard, Beckett pressed to his chest, her head rolling back and forth on his shoulder as her heels dig into the mattress.

"Fuck," she swears, biting her lip to keep from choking on all the air she's trying to gulp down, hips straining against Castle's hands and then she's shaking, bowing, his voice in her ear as she snaps, body flooding with a heat that starts right between her legs and sweeps outward like fire.

Heat, hilarious.

"God Beckett, you didn't even make her work for that." His open mouth closes around her neck, sucking as he trails a wet path up to her ear, grinding against her back a little bit.

Beckett's eyes finally blink open, hazy and unfocused, black with desire as she licks her lips and regards the woman crouched in between her legs, all blonde hair and red lips, shiny with her.

"Don't worry," Natalie says, biting down on Beckett's inner thigh hard enough to make the other woman jump. "I'll work for the second one."

Beckett barely has time to breathe before she's sucking in a sharp breath again, Natalie's mouth vicious and unrelenting against her. Castle's watching, pressed cheek to cheek with her now, his other hand moving from her hip to cup her face, brushing some of the wild hair out of her eyes.

"Can you see?" He's watching and he wants her to watch too, watch how much she can't keep still, how Natalie works her like they've been doing this for years, like they do it more than on occasion.

Beckett opens her eyes, slides them downward until she's seeing what Castle's seeing, and he can feel her hips twitch up at the sight. "God," she breathes, reaching her hand up behind her to tangle in his hair, gripping him hard as her hips rise up to meet the sharp flick of Natalie's tongue.

Natalie stops when she notices them watching, grinning up at them with bright eyes. "Is she always this wet?" she asks as she dips a finger downward, slides it until Beckett can't stop making this noise

"She is really, really into this."

"I'm right – " Beckett starts to say, trails off on a gasp when Natalie ducks her head again, sucking this time. "I'm right here." In a moment of self control, Beckett lets her hips rotate back against Castle, who is more than a little bit into this whole situation himself, right up against her back.

His voice is right back at her ear again though, driving her insane as Natalie works her harder and harder. "Are you saying you're not really into this?"

She can't answer, can't make words when everything just feels so good. He won't let it go though, dropping the hand tangled in her hair to slide itself onto Natalie's head, cupping her as she bobs, works, plucks Beckett like a master.

"Exactly how hot does it make you, knowing another woman is going down on you right now, Beckett?"

She can't breathe, can't think as Natalie groans out a laugh between her thighs that feels more like a super concentrated vibration, right where she's most sensitive. He lets his hand move from Natalie's hair to trail a finger down her jaw, feeling her mouth working as he and Beckett watch. The pad of his thumb brushes Natalie's bottom lip, trailing through the moisture there, feeling them both until Natalie switches direction and sucks Castle's finger into her mouth.

She gives him a dirty little smirk as Beckett swears hotly, hips grinding up into nothing at the sight of Castle's finger surrounded by those lips. He pops his thumb out eventually and then Natalie's motioning with her eyes and Beckett wants to sob when Castle's thumb presses hard on her.

"Can one of you just…" she trails off as Castle's finger slides just a little bit to the right, right to that spot she has, and then she's yanking on Natalie's hair because it's the closest thing she can reach, trying to push her or pull her or something she doesn't even know she just needs, she just needs –

"Both?" she hears Natalie say, voice lilting with that tone of challenge she always gets when they're doing this, and then Castle's hand and Natalie's mouth are on her at the same time and when she comes she can't even remember her own name.

Part of the draw for Natalie, taking up a recreational spot firmly in the middle of an already established pair, this pair, is the way Castle and Beckett are with each other. They're fantastic lays, the both of them separately, but being in the middle of that much intensity is more than a little bit intoxicating. It's like a contact high, being around them, near them, touching them when they're doing this, and she suspects it does just as much for them to be able to show it off a little bit.

They're both between her legs, now, as she fists a handful of Beckett's plum colored sheets over her head, blonde hair spread wild and wide across her queen sized mattress, hips straining.

"Like this," she hears Beckett say, and then her pointed little tongue is on her, and she feels stars behind her eyelids. Thin fingers grip around her right thigh, thick ones around her left as she glances down her own body, watching as Beckett's head pulls back a little bit and Castle's replaces it. He mimics her previous movement, this time with his heavier, thicker tongue but oh god it's right where she wants it, a perfect contrast to Beckett's, and a deep groan spills from her lips as he keeps going and going and going until fuck.

When she opens her eyes again, Castle's grinning at Beckett, looking proud of himself, as the other woman brings up a hand to cup his face, grinning too, and then they're kissing each other between her spread legs, groaning as she watches their tongues slide slippery against each other, the taste of her in their mouths.

And doesn't that almost completely do it for her.

They're all over each other then, Castle's just about hitting his limit, the only one who hasn't had some kind of relief, and with Beckett so close, he can't hold himself back. Beckett grunts loudly as he pins her to the mattress with his body, mouth taking hers over and over until he buries his face in her neck, spreading her knees with his own.

Natalie drags herself across the bed and out from under them, flipping over onto her stomach to watch, eyes alternating between the blissed out look on Beckett's face and the steady roll of her hips against Castle's. She slides a hand underneath herself as she watches them, down her belly and between her own legs, fingers sliding easily through the moisture Castle and Beckett have left in their wake.

Beckett's head tilts back into the sheets the second Castle strokes into her, her teeth leaving white marks in her bottom lip as she tries to hold back the noise rumbling up out of her chest. Natalie can't help but reach out and trail a finger through the other woman's dark, damp hair, wanting to feel a little of what she's feeling.

Beckett's eyes slide open when she feels the brush of Natalie's hand, locking hot, unfocused gazes with her. It does not escape her notice that Natalie's other hand is otherwise occupied, buried deep and far away, her hips rocking rhythmically just close enough for her to see. Now that she has Beckett's attention, Natalie lazily lets her finger trail down her pink cheek, around her chin, across the kiss swollen swell of her bottom lip. The first syllable of Natalie's name spills from Beckett's mouth haltingly at the touch as Castle pulls back and then presses forward and into her again. She's having a lot of trouble concentrating, so she stills him with a hand on his shoulder, biting down on the pad of Natalie's finger at the same time. Both of her partners groan at her opposing movements, stop and go, one for each of them, and then she's reaching for Natalie's shoulder and tugging her closer.

Beckett doesn't even know what she's asking, pulling on Natalie, but she comes closer and Castle sits up a little, kneeling between her legs, trying to be still as he watches them.

Beckett twists to her side a little bit, lips and tongue connecting with Natalie's stomach, right below her belly button, making the other woman twitch a little bit, but she can't quite reach her anywhere –

Before Beckett can even try to rearrange their positions in her lust swamped state, Natalie throws a thigh over her head, kneeling right over her face.

"Oh my god," Castle croaks, grinding his hips into Beckett's completely on instinct. She gasps as he does, steadying herself with two hands bracketing Natalie's waist, and then things just start to happen as Natalie leans forward and over her face, and Beckett's mouth just connects and then everyone is groaning and moving and grinding and and and –

Beckett feels Castle's fingers press against hers, both against the skin at Natalie's hip, stilling her movements just enough for Natalie to sit herself up a little to glance back at him. He wants something, this is clearly evident on his face, eyebrows screwed together as he stares at them, stares at her, at where Beckett is between her thighs though she knows he can't quite see anything, and oh.

Natalie stops moving against Beckett's tongue (which is about a hundred times harder to do than it sounds), pulling her hips away enough for Beckett to flop her head back down and breathe out a what?

"He wants to watch," Natalie tells her, smirking, throwing a glance back in Castle's direction. Beckett lifts her head and peers around Natalie's body, see's how tense Castle's face is, he is so, so far gone, but he definitely looks like he's not arguing.

"Turn around." Beckett's voice is raw as Natalie swings off of her, rearranging herself so she's facing Castle. His hands immediately tighten on her own hips, his strokes getting sloppy and hard between her legs as her mouth opens against Natalie again and again, where he can see it this time, and then Natalie's grasping for one of his hands, pressing his fingers against her too, and Beckett can feel him there, brushing against her tongue and it makes her slam her hips up, bowing sharply at the thought of them all mixed together like this.

It's all one giant cloud of bliss after that, Beckett's pretty sure Natalie comes first, grinding tightly against her mouth and Castle's hand, and then ends up somewhere next to them as Castle reaches underneath his brunette detective, pulling her mouth to him by the back of her neck and crushing her with the force of his body driving erratically into her until she can't stand it anymore and bites him hard on the shoulder, shattering around him until he flops spent on top of her.

She pushes him off after her arms start to work again, panting harshly as she drags the back of her hand across her mouth. Natalie groans from beside her, watching apparently, and then the blonde's mouth is crushing against hers, a thank you or something, Beckett's not quite sure, but it's affectionate and welcome, and she's just too loose to even care about anything except never moving ever again.

Castle kisses her once on the thigh, too, open mouthed and warm, and she lets her hand card through his hair at the gesture, smiling.

Beckett is always surprised when mornings after with Natalie Rhodes are the exact opposite of awkward. The other woman is so practiced at being at home in any situation, it leeches into everyone, leaving them all just this side of normal. Castle makes them coffee, lets them tangle against each other and the sheets for just a little bit longer in the morning, but then Natalie's up, showering, throwing her designer duffle bag over her shoulder and giving them both warm hugs and a wink as she heads for the airport or the studio or wherever she's supposed to be with an unspoken until next time hanging in the air between them all.

Castle always winks back.

Beckett can usually do no more than slide a satisfied smirk in her direction.

(They are really, really skilled at double teaming her.)