A/N: A HUGE thank you to Team Cheersqad: Anja, Katherine, and Lindsey, for betaing and for cheering me on. I love you girls so, so much, and I'm so thankful to have you on my side. Special shout out to Angie/dtreker for the cover art - this amazing lady went back to the drawing board for me FOUR TIMES for me, and I am so incredibly grateful.

Castle belong to AWM and ABC

INTERPOSE

/ɪntəˈpəʊz/

verb

To place or insert between one thing and another.

"She interposed herself between the newcomers."

Synonyms: insinuate, place, put.

7x06 AU on the Canon!AU

He awoke in a reality that was not his own. An alternate dimension. One, he quickly discovered, in which there was no Beckett in his life, he was estranged from his daughter, his mother was… well… at least this reality was positive for someone? As for himself, he was even more of a self centered jackass than he had been in the pre-Beckett era.

The truth of it was staring him in the face.

Literally.

Whatever that object was had transported him into a world that already had a Richard Castle. And rather than switching them, or placing one in the other's body, or making the other magically disappear in order for the cosmos to teach him a lesson à la It's a Wonderful Life…

This reality now had two Richard Castles.

It had to be a dream, but no matter what he did, he couldn't find a way to wake. This alternate universe he found himself in was so close to his own reality, but the differences were jarring. The boys treating him like a stranger. His loft overrun by his apparently successful mother. His relationship with his daughter in tatters.

And in this world, he had never met Beckett.

Getting in on the investigation? He knew how to do that. Repair some of the damage to his relationship with his daughter? He might mess up along the way, but it was worth the effort. Woo Beckett once more?

That one he wasn't so sure about, for a number of reasons.

Did it count as cheating on your fiancée when the person you're wooing is an alternate dimension version of your fiancée? Did that make them the same person, in spite of the brittleness that this Captain possessed in place of the soft spaces he had found in his own Detective? (Soft spaces that apparently his own presence in her life must arguably be at least partially responsible for?)

And then, as if that wasn't confusing enough, he showed up. As in, himself. His double? The version of him that existed in this reality. Because in spite of him coming to this universe, the him that was already here… didn't go anywhere.

He supposed he should be relieved. This version of him was a jackass, and at least his own Beckett and Alexis would never be exposed to this version of himself.

It was also weird, he thought, to be the third wheel on a date that wasn't a date between himself, who was not himself, and his fiancée, who was not his fiancée, when the two of them were strangers to each other and yet…

...and yet.

Dinner was kind of a date but it was also him getting in on the investigation. But as they ate and talked and he watched himself flirt with her and her shut him down in a way that wasn't a no, and then turn around to him and use her bedroom voice, casting looks at his other self all the while… It was eye opening to see the tug between them, the way they bantered and flirted. It was odd to be outside of that, yet drawn in.

And it was downright weird to see himself who was not himself lean right into his fiancée who was not his fiancée's personal space and invite her up. Weird and hot, because he knew the way her eyes flashed and darkened as they stared first into his-who-was-not-him's eyes, then straight into his own before nodding her assent.

Fire sizzled down his spine. He knew that look on Kate Beckett's face. That was her let's-pull-out-the-kinky-box look. Her take-me-in-the-elevator-because-the-bed's-too-far-away look. The next-time-without-the-tiger look. Without the tiger, because she was the one on the hunt, and he was always more than willing to be her prey.

Except.

Except he wasn't sure, didn't know. Was this cheating? This was his fiancée! But it wasn't her? But it was?

"I, ah… I'll leave you guys to it then?" he squeaked as they entered the loft. "I'll sleep in the guest room."

Her hand on his arm stopped him.

"Come with us, Castle," she said.

"But I'm… you're not…"

"If you don't want to join in, you could always just watch. Isn't that right, Rick?"

"Technically," his other self agreed, "We are the same person. So really it would just be you watching yourself be with your wife."

"Fiancée," he corrected automatically. "The wedding got postponed. It's a long story, actually. See I got kidnapped and my memory was wiped and…" his voice trailed off as he took in the two blank stares directed at him. "Never mind," he mumbled.

Captain Beckett looked up at him with those liquid eyes he had never been able to resist. "Are you trying to tell me that you and your fiancée have never filmed yourselves and then watched it together?"

He did not consider himself to be a blushing man, but he was well and truly caught.

"This is no different, Mr. Castle," she said, taking his hand in one of hers and slipping the other into his other self's, then allowing his other self - dammit, this was confusing - to lead the three of them into his bedroom.

Beckett took command once the door was safely shut, turning to push him into the armchair in the corner he sometimes sat in with his morning coffee after he had seen Alexis off to school. "Castle, you sit here. Rick," she said turning to his other self. Oh, he liked that as a way to mentally differentiate himself from his other self. Because Rick was who had been before Kate, and Castle was the man he had become thanks to her influence. "Strip."

He watched Rick's eyes darken, fingers moving of their own accord to the buttons of his shirt. Honestly, his own fingers itched to do the same, muscle memory from that exact command coming in his own Beckett's voice, but for now he refrained. Well, he popped the top button of his shirt, suddenly finding all his clothes a little too restricting. There was something incredibly arousing in getting to watch himself strip and then meet the hottest woman he had ever laid eyes on whom he happened to be in love with for a scorching kiss.

Then Captain Beckett began peeling off her own clothes, and all thought fled.

She had been burning since the moment he walked into the precinct, those blue eyes lighting something within her she had thought long dead. Then when he had shown up at their date (date! With her all-time favorite author! The man who had secretly topped her freebie-five list for years!) with his other self, providing unquestionable proof that his somewhat outlandish story might actually have some merit - well, she wasn't going to complain. The differences between the two Richard Castles were fascinating - one a cocky playboy, a bit of an asshole with undeniable charm and a heat between them that had her clenching her thighs under the table even as she resisted the urge to pop him one right between the eyes; the other was... Calmer? More restrained? Yet watched her with unmasked longing and deep adoration. She was astute enough to know the difference between the one finding her physically beautiful, and the other appreciating the beauty in her soul.

It was unnerving. She hadn't shown anyone a real glimpse of her soul since… had she shown it to Sorenson? She doubted it. Royce, then, probably, when she had been too green and too desperate and too infatuated to hold her heart back, and he had rejected her anyway. Yet this man seemed to not only know it, know her, but loved her in a way that was real and deep and lasting.

Clearly he was insane.

Except, she decided as she commanded the one to strip and the other to sit, and began to remove her own clothing as efficiently as possible, the evidence was right in front of her.

On display, one might say.

Rick's pants dropped, and then his boxers.

All of it. And there was a lot of it. Right there.

Undressing under the eyes of two men who were both watching her with identical looks of desire was powerful. She threw a smirk over to Castle, in the chair, watching with rounded eyes and unmasked desire, then sauntered up to Rick. He trailed a fingertip up her arm, leaving goosebumps in its wake, his eyes perusing her body with the lazy hunger of a lion who has already caught his prey and is preparing to feast.

Rolling onto her toes, she took his mouth with hers, commanding and dominating him. She had assumed he would submit, but instead he simply humored her, allowing her to take what she wanted for a time, and then, when he was ready, he pushed back, wresting control from her, nipping and biting and sucking his way down the column of her throat, walking her backwards til her knees hit the bed, following and controlling her descent so that before she knew where she was, her breast was in his mouth and his fingers were stroking through her already damp curls and she was grasping the bedspread beneath her as his mouth moved its way down, over her bellybutton, detouring down her hip and thigh, then back up the inside of her leg before finally, finally, letting himself taste her heat. Her hips arched off the bed, and she felt him band one strong arm around her to hold her down, the other moving to the inside of her thigh to hold her open as he began to feast on her. She felt his tongue pierce her, occasionally lapping upwards to flick her clit before heading back again, and whichever way she looked, either down her body or to the side, there was a pair of midnight blue eyes watching her as she fell apart around his mouth.

It took her a moment to come back to earth, but when she did, she could hear the sound of a drawer being shut and the rustle of packaging being opened. Then Rick was hovering over her once more, his cock bumping against her leg as his bent over her to kiss her.

"Permission to come aboard, Captain?" he asked between kisses, stroking himself against her, gliding back and forth in her wetness. In a surprise move, she tumbled him over so that she was straddling him.

"Permission granted," she replied, taking his latex-sheathed cock inside her, letting out a groan as her inner muscles stretched around him. He was big, and it had been a considerable dry spell for her, so she took a moment to breathe and adjust, and was pleased that he waited until she began to move before beginning to thrust up into her.

Their movements were uncoordinated at first as they struggled to find a rhythm that worked. Then their eyes locked, and she ground down as he jerked up, and their mouths met, and everything just clicked. She found herself riding him with abandon, his short strokes meeting her, spurring her on. He sat up a little more, changing the angle to something deeper, his mouth moved along her jaw and nipped at her earlobe as one hand drifted around her hip, squeezing her ass, then one finger played lightly over her butthole.

"Before tonight is through," he panted in her ear, "I'm going to take you here, too," he said, dipping his pinkie in. The sensation shot through her, his other hand tweaking her nipple at just that moment, and she was gone, riding the wave of her orgasm as he gave a hoarse cry and rutted into her.

They collapsed together in a tangle of limbs and it was several minutes before he rolled away, patting her ass in a "be right back" motion before heading into the bathroom to, she assumed, deal with the condom.

Raising herself on one elbow, she observed Castle, shifting in his chair, his expression dazed and slack-jawed, a very impressive tent visible in his pants.

"Still determined not to join in?"

"I just think that this should be something between the two of you," came the reply, but his tone was so unconvincing she raised an eyebrow, silently calling him out. He grinned at her sheepishly, and shrugged.

That sure looked like permission in her books.

She rolled over onto her hands and knees, crawling toward him across the bed, getting unsteadily to her feet so that she could cross to him, sinking to her knees once she was between his, taking her time so he could say no if he was really determined to not join in. It was a simple matter then to draw his zipper down over his straining erection, tug his pants and boxers until he lifted his hips and she could guide them down to pool at his ankles, and take him into her mouth.

He was big, just like his counterpart, and long, that delightful texture of velvet-over-steel. She took him in as far as she could manage, revelling in the little yelp he gave, smirking up at him. Releasing him with a teasing pop, she began to lick him with long, languid strokes of her tongue, her hands drifting up his thighs to play with his balls.

"I thought I would need a few minutes to recover, but damn if that isn't a sight to behold," Rick said behind her. She glanced around to find him leaning against the door jam watching them lazily, his cock already half-hard and in his hand. Rather than responding verbally, she nodded him over and sent him her best bedroom eyes. He almost stumbled as he crossed the room, detouring once more to the drawer.

She returned to her task in earnest now, licking and sucking, using her hands in tandem to stroke him, taking him as deep into her mouth as she could manage. Castle was panting now, shifting awkwardly as if to stop himself from thrusting into her mouth with abandon and this determined care for her from both men had arousal coiling in her core.

She felt a hand stroke down her back, two hands massage her butt, knees nudging her own a little wider apart. A single fingertip stroked down to her core, sliding inside her with ease. She clenched around it, desperate to ease the burn but finding it only stoked the flame within her. Behind her, she could feel Rick sliding his cock through her folds, then gasped as he pressed inside her once more. His strokes behind her were languid but deep, and she eased off her own frantic sucking to match his rhythm. Before her, Castle whined in his throat, and she grinned deviously.

Then Rick's finger found her hole, and she cried out in a curious mix of both pleasure and pain.

"What do you say? Want to take her from the front while I take her from behind?" Rick asked, a leer in his voice that she should have found irritating if it hadn't made her wetter, even as he continued his ministrations from behind. She had all but given up on the cock before her, lost to sensation.

"If Beckett's game," Castle agreed readily, grinning down at her. She smiled back, a little hazy, and watched as he stood, stepped out of his pants, removed his shirt. "The bed would be best, wouldn't it?"

"Our knees aren't as young as they used to be," quipped Rick, sliding out of her - now it was her turn to whine - and between them the two men helped her to her feet.

Castle laid back on the bed, arranging the pillows so that he was propped up, and Rick handed him a condom and some lube, the latter of which he took back once Castle was done with it, making sure to apply it liberally. Beckett watched the two preparing calmly, finding their matching confident preparations - because it was uncanny watching two men move in exactly the same way - and found herself feeling more aroused and more than a little excited at what was about to take place.

Then Castle held a hand out to her. "Join me?" he asked, those damn heart eyes ripping her defenses to shreds, and she found herself compelled to place her hand in his, his blue, blue eyes casting a spell on her soul. He looked at her like he knew all her dark places, and loved her anyway.

She bent over him to kiss him, and found herself melting. Where Rick had been fire and heat, Castle was tenderness and desire. The similarities and contrasts between the two men was making her dizzy, and as Castle drew her closer so that he could nibble his way along her jaw to a spot just behind her ear that had her keening, her last coherent thought was that she never wanted to think straight again.

Castle's hands hadn't been idle - she had noticed how tactile both men were, how rarely they were completely still - and she arched beneath his touch as he stroked her skin, caressed her breasts, fingers touching and guiding with just enough pressure to make her melt, seeming to know at each and every spot just how to touch her. She felt him guide her over him, shifting at his nudge to straddle him, and then one hand snaked down to slide through her folds, a gentle tease that had her arching into him even as his mouth travelled down her neck, using that arch of her back to pay homage to her breasts, teasing her nipples into peaks with nips and sucks.

"Castle," she gasped, eyes clenched shut, and she felt him grin around the breast in his mouth, whined as cold air replaced his warm mouth on the sensitive nub.

"Are you ready?" he asked and as she nodded he dropped his hands to her hips, aligning himself so that she could sheath herself on him. His eyes held hers as he filled her slowly, inch by inch, and she was powerless to look away.

He was the one who broke eye contact, looking over her shoulder as the mattress dipped behind her.

Then Rick's voice rumbled in her ear. "Are you sure you're ready?" His fingers traipsed lightly down her back, gently tipping her forward, then squeezed her ass as once again his finger dipped into her. She jerked forward, grinding down on Castle, who, on reflex, thrust his hips up into her, both emitting groans. Rick continued to stroke her from behind in short probes, adding a second finger, his movements behind her tipping her forward in short, shallow strokes that left both her and Castle panting.

Then he removed his fingers, and she felt the blunt head of his cock nudging her from behind.

The pressure as he eased into her was intense and a little sore. He went in slow, careful thrusts, making it as easy on her as he could. It wasn't her first time by any means - she had done all kinds of things in her adventurous youth - but her dry spell out dated her Captaincy, and her muscles were unused to being stretched in this way. Finally, finally, he was all the way inside her, and she could feel the pulse of both men within her, stretching her fuller than she had ever been. There was a pause as they allowed her to adjust, and she took a few deep, shuddering breaths as her body acclimated to the sensation of being so thoroughly filled.

Then Rick began to thrust, rocking her forward onto Castle, setting a rhythm that Castle beneath her was able to match. She braced herself on Castle's shoulders, arching her back, mewling as the two men moved within her. A small orgasm washed over her, leaving her gasping, and this seemed to be the signal to both men to stop holding back. Hands tugged at her breasts, glided down her sides, branded her hips, kneaded her ass - she had no idea which was whose; all she could do was brace herself and call out encouragements as she was fucked in both holes, hanging on for dear life as they both lost themselves in her.

Behind and beneath, both men seemed to be getting sloppier with their thrusts, the crescendo building, and just as she wondered if there was any chance of her getting there before them, fingers slid between her folds, finding her clit and circling it with fingerpads, sending her flying before both men erupted, rutting into her, pumping her full, prolonging her release as wave after wave of pleasure flooded through her, scattering her thoughts and emotions on the tsunami of relief before she collapsed onto the broad chest beneath her, spent.

Rick eased out her, flopping to her other side as all three lay there panting, trying to catch their breath as they came back to themselves.

"Well, Castle, when you get back to your version of me, you'll have quite the story to tell," she mumbled. She dragged her eyes open to see his blue, blue eyes sparkling down at her.

"Give me about twenty minutes and we can add to that story if you like," he grinned boyishly, and on her other side she felt Rick lift his head.

"Twenty minutes? I'm game."

She bit her lip and rolled onto her back between the two men, bracing herself up on her elbows for a better view of the two identical bodies on each side of her - and in particular, and the two cocks already half hard again.

"Make it fifteen," she said with a smirk.