Research Assistant

Summary: Beckett helps Castle research for a book. Caskett.
Rating: M. Not for the kiddies.
Disclaimer: Castle is owned by ABC and this story was written for purely entertainment purposes, nor do I make any profit from it.

So, um, yeah. I – just – I don't even know what happened here. It just kind of happened and I'm not sure how.

Inspiration for the story comes from "Sexual Kinetics," a stunning Law & Order: CI fic which I highly recommend. Inspiration for the sexy somes from the wonderful writing duo chezchuckles and Sandiane Carter, because their stuff is so full of the sexy that I really think it might be contagious.

"Let me get this straight. You asked me to come over here so you could handcuff me to a bed?"

"Well – yes, but it sounds creepy when you say it like that."

Kate sighed heavily. She'd been almost done at the station when he'd called to say he was writing and if she was free, could she try out a scene for him? She'd consented with only a little suspicion; she knew he tested situations before he put them in books, and to be honest, she was surprised he'd never asked her before now.

It turned out that he wanted to handcuff Nikki to a bed. He needed to know if she could get free, or if he'd have to figure out some kind of subtle deus ex machina. And she couldn't help wondering if this was completely unrelated to the book anyway.

"Beckett, I promise this is essential to my novel."

He must have read her suspicion. "Sure it is."

"Besides, I will sit outside the room with the key and leave you in privacy. I'm not going to just stare at you like a pervy old man. You can just tell me what you figure out."

"Why aren't you doing this? Why do you need me?"

"I don't have handcuffs." She shot him a look. "Seriously. I don't. But you do. And Mother and Alexis are both out till tomorrow, and I'd rather not handcuff myself if I'm going to get stuck till then. Since I'm not sure if this will work."

Beckett folded her arms. It actually sounded legitimate. Which was as troubling as the alternative, in a way. "I'm still not sure this is a good idea."

"I'll make it worth your while. Here. I'm willing to barter for this." He handed her an index card.

She scanned it. He'd written, in black marker, Castle will stop! "What's this?"

"A magic formula. Once a week, if I am irritating you or bothering you or making you unhappy in any way, you use this card and I will stop, right then."

She stared at it and couldn't help but chuckle. Where was this card when they'd first met? "Once a day."

"Twice a week."

"Done." Better than nothing.

"Absolutely not."

He stopped for a second and tried to think about it from Beckett's point of view. Okay. She was right. It was awkward enough to ask her if he could handcuff her. Maybe doing it in his bedroom was a little over the top. "You're right. That's weird. Spare room?"

"How gentlemanly of you."

"I aim to make bondage a pleasant experience."

He cuffed her hands to the headboard and carefully tied her feet to the end of the bed; she'd left her jacket and holster on a chair nearby. "Are you okay? Is this too tight?"

She let out an uncomfortable noise. "I'm trying to ignore how incredibly disturbing this whole thing is."

"Just research, Beckett. I do weird stuff like this all the time. You comfortable?"

"Relatively."

"Are you regretting that you agreed to do this?"

"Yes."

"I guess I'm not really surprised. You sure you're up for this? You really don't have to if you don't want to."

"As long as no one ever, ever finds out about it."

"Fair enough. I'm leaving the key right here." He placed it on the nightstand, which was far enough away that she doubted she'd be able to reach it. "I'll be outside, so if you need something, or if you get uncomfortable and you want to stop, you just call and I'll be right here."

"Great."

"Good luck." He stepped out, leaving the door open, and she heard the soft puff of the cushion as he sat down in the chair he'd dragged out into the hallway, the soft click as he started typing.

Alone.

Satisfied he was holding good to his promise to leave her alone until she called him, Kate took a deep breath and took stock of her situation. Her handcuffs, obviously, were solid. The key was out of reach; if her feet were free, she might be able to get to it, but even then she wasn't sure she'd be able to unlock them. She tugged experimentally at her feet, but Castle was good with knots and she couldn't get enough leverage to get free.

She tried her hands next, flexing and releasing the muscles in her wrists. No luck. The cuffs were just tight enough that her wrists were securely held. Twisting her elbows, tucking her thumbs into her palms. Still nothing.

She twisted her head up to examine the headboard he'd handcuffed her to. It was solid, sturdy. She pulled, but she could tell the oak was far too strong. Again, if she'd had full use of her legs, it might work, but as it was, she couldn't break it to free her hands. Though out of respect for its owner, she probably wouldn't do it anyway.

So far? A whole lot of nothing. Damn.

On the other hand, she understood why Castle hadn't wanted to do this alone. Without an extra person, he could've been stuck for the night.

Time to gracefully admit defeat, seeking solace in her new magical index card. An evening not quite wasted, if it meant she could shut him up. "Castle?"

Seconds later, he poked his head in. "No luck?"

"I don't think I can get free."

He nodded slowly. "I kind of suspected, but I wanted to check."

"With my feet like this, I can't really do anything."

He was coming closer, watching her, sitting beside her as he paused to untie her feet. Kate flinched a little nervously as he straightened and looked down at her. Lying helpess, completely vulnerable. It was –

"What if – well, what if he came back? Maybe Nikki could actually fight him off,then get free?"

She didn't respond immediately, and he looked down at her curiously. "Beckett?"

She met his eyes. He took in a breath. Her cheeks were flushed (from exertion?), her breathing heavy…and her pupils were dilated, the dark almost swallowing the hazel irises. Dark and deep and staring at him.

His breath caught in his throat, because he'd seen her irritated, frustrated, even scared. This wasn't it.

Kate Beckett was aroused.

The thought hit him like a stone and then he couldn't stop thinking it. Her huge, liquid dark eyes, her lips parted as if in anticipation, her chest heaving, her breathing shallow. She was handcuffed to his bed. And she wanted him.

And he vaguely realized that it was deeply wrong for the sight of someone so strong and independent tied up and completely in his power to be so hot but oh shit he wanted her so badly.

She swallowed, seeing his eyes darken as he looked down at her, and a shiver ran up her spine as she felt a wave of arousal rush through her body, her fingertips tingling, her skin buzzing with it, powerful as a lightning bolt. She'd never let a man take control of her. Certainly never let one restrain her. But as she looked up at him, she couldn't slow her pounding heart. Because she trusted him.

She licked her dry lips, her stomach clenching as she saw his eyes focus immediately on her mouth. Oh. Oh. Images flashed through her mind, unbidden, wild, dangerous, images of all the things he could do to her, all the places he could touch her, all the ways he could make her beg –

"Kate – "

She met his eyes, scared and turned on and not sure what to do.

But wanting. So much her body ached.

"Kate, if you tell me to stop, I will."

His voice sounded strangled. Thick. Low. Intimate. She bit her lip, trying to slow her erratic breathing, her heart hammering uncontrollably, her whole body burning, fiery and shivery and tingling. Her eyes widened, a sharp breath escaping her parted lips before she could stop it. Oh, God. He was – he wanted – all she had to –

Castle will stop.

She met his eyes, dark and heavy with desire. "Don't stop."

Castle's head spun as he realized she'd just given him permission. She was giving herself to him. Offering herself. As if I could ever deserve her.

It vaguely occurred to him that he shouldn't be thinking of her as a gift, as his, because she was a woman, a strong, liberated woman, full of briliance and courage and independence, but all he could think was She's letting me.

With a silent apology to Susan B. Anthony, he leaned forward, breathing in the scent of her soft hair, her warm skin, and took his life into his hands.

He kissed her slowly, delicately, her lips under his so gentle that his chest tightened. Because she was kissing him back.

Oh God.

He was so gentle. So painfully gentle. Her body tensed, her breath caught against his mouth, warm and soft and velvet and searching. Her head whirled, every nerve ending in her body on fire, because she was completely out of control. But she felt safe.

He caught her bottom lip between his teeth, laving over it gently with his tongue, feeling her gasp against him, her mouth soft and wet and opening obediently under his. He wanted all of it. All of her. He wanted to explore every corner of her mouth until she had no more secrets and she couldn't breathe without his taste lingering on her tongue. He wanted to touch her until she felt his hands on her skin every time she moved, until he was all over her permanently and she could never, ever escape him and she wouldn't even want to.

His kisses went from soft to aggressive, his hands on her rougher, possessive. She gasped as his fingers crept under the hem of her shirt, his hands on the bare skin of her stomach hot and searching, touching her like she was his, like he knew her, like he was marking her as his own. She wasn't in control. She was shivering and trembling and waiting to see where he would touch her next.

Castle kissed her throat, his tongue flicking out to trace the line of her neck, and Kate tugged helplessly against the handcuffs, straining, desperate to touch him. He seemed to sense her frustration; she felt his lips curve into a smile against her throat before he continued. She gasped as he ran his hands slid under her shirt, running slowly up her sides, learning every curve, every inch of her silky skin, the soft flush of her breasts. Heat burned slowly along the trail his fingers left.

She tried to speak, but he swallowed her words with another kiss, his tongue stroking roughly over the ridge at the top of her mouth, and whatever she meant to say ended up as a high-pitched moan somewhere between his tongue and hers. Castle was leaning over her, his body pressing more and more into hers, warm and solid and heavy and too good but she didn't care. All he had to do was lower himself a little more. She had to keep herself from pressing her hips harder into his, leaning in to increase the friction driving her crazy.

Castle forced himself to stop and breathe. Her body was pressed against him, long and lean and warm and flush so that he almost couldn't think. Her silky skin and hair under his hands was dizzying, addictive – he couldn't stop touching her – but he had to be sure. She was only his if she truly wanted to be.

He couldn't bring himself to pull away, so he brushed his thumb softly over the smooth skin of her stomach, feeling her muscles tensing under his touch. He kissed her cheek before whispering into her ear, "Are you sure?"

He was asking her permission. Never assuming. Never taking her for granted. Never pushing. He would stop when she told him to. She wasn't sure exactly where the line was now. Because he was letting her draw it.

(Castle will stop)

"I'm sure."

He leaned over her to suck at her earlobe, his teeth nipping lightly, and her eyes shut as she shivered at his hot breath on her neck. His knee slid between her legs, and she instinctively arched into him, feeling his sharp intake of breath as the hardness of his strong thigh pressed against her. A wave of heat flooded her body, a shiver rolling through her spine, the pool of heat in her center getting tighter.

He rocked against her, hitting her in just the right spot, and she let out a strangled, breathy gasp. "Oh – oh Castle – "

He groaned, because his name slipping between her red lips like that, hot and breathless and begging, sent a jolt straight to his groin because he wanted to do bad, bad things to her. All over her. Until she cried out his name in helpless abandon. He slowly unbuttoned the top button of her shirt, his mouth going dry at the pale skin and milky-white lace that filled his view.

He traced the dip of her collarbone with his tongue, feeling the sharp breath she drew in, and sucked gently at her pulse point, not hard enough to bruise, just hard enough to make her breathe his name against him in a shaky whisper. He could feel the blood coursing south, his body tightening. Either this was stopping soon, or he was going to take her, right here, right now, take her so hard –

The shrill ring of her cell phone shattered the heated moment, her whole body tensing at the unexpected clamor. Their eyes met, startled, and for a second she didn't know what it was because holy shit she was way, way too close to letting Richard Castle strip her naked and make love to her in his spare bedroom and there was no room in her brain to process anything else.

"Castle – can you – " it took her second to get her voice working again, but he understood and reached over, pulling her phone out of her coat pocket because he knew that's where she kept it. He pressed Talk and leaned over her to hold it to her ear so she could answer before it went to voicemail. Her eyes never left his as she cleared her throat. "Beckett." Her voice was shaky.

Castle felt himself exhale nervously, watching as she listened quietly. "Okay. Yeah, I'll call him. See you there."

The call over, he set the phone down. "Here." He picked up the key from the bedside table, unlocking the cuffs from her wrists and giving her a hand to pull her up. She sat up slowly, taking a deep breath, tucking her hair behind her ears. Her heart was still hammering uncontrollably, her lungs gasping for air, her whole body warm and humming with want.

She put her head in her hands, taking deep breaths. She felt a strong hand on her back, gentle, unassuming, letting her know he was there but waiting for her. "You okay?"

She nodded slowly. "I'm fine."

Castle wondered if maybe he'd pushed her too far. She looked as shaken and stunned as he felt, because holy shit, did all of that just happen?

But she wasn't pulling away. She wasn't telling him to leave.

And she knew that if she'd asked him to, he'd have stopped.

Kate wanted to talk to him, but had no idea what to say.

So she reached for his hand, squeezing it gently before letting go. "Come on, Castle. We've got a case."

And instead of simply following her, as he usually did, Castle surprised her – he leaned in, brushed her hair behind her ear, and kissed her forehead softly. "I'm right with you, Detective."

They had a late night at the scene, an early morning the next day, and if not for the softer look in her eyes, the smile that seemed to be hovering whenever she looked at him, and the way her hand lingered on his when he handed her coffee, Castle might have thought the whole thing was just a dream, a random half-crazed fantasy born somewhere between Nikki Heat, little sleep and too many cups of coffee.

The knock at his door that night was somewhat of a surprise, but the person behind it wasn't.

"Kate – "

He never got the chance to finish what he was going to say, because she pulled his face to hers and kissed him.