ON THE EDGE
A 2x18 AU

"If it wasn't for Nikki Heat, this guy would have just gone on killing because he wouldn't have met anyone smart enough to catch him. I'm speaking, of course, about Special Agent Shaw."

Kate bites the inside of her cheek to keep from grinning, and she lobs a hand towel at him. She can't stop the smirk of satisfaction when it hits him square in the face, and she stands, wipes her palms on her thighs. It's been a long few days, and she's exhausted. Her body aches, her eyes scream for relief, and she just wants to collapse in what's sure to be a sinfully comfortable bed.

"Good night, Castle."

She hears him set his mug down, and she's almost at the stairs when his hand lands on her shoulder.

"Hey," he says quietly, stepping around so he's in front of her. "I'm glad you're here, Kate. I'm...I'm glad you're okay."

Kate gives him a smile. "Thanks for letting me stay."

"No need to thank me, Kate. You're welcome anytime." His hand stays on her shoulder, thumb circling close to her collarbone. He looks nervous and indecisive, his tongue darting out to wet his lips, before he seems to come to a decision. His grip tightens on her shoulder and he tugs, pulls her into the wall of his chest.

Kate tenses at first, the surprise of the tight hug paralyzing her. But after a moment her arms wrap around his back and she hugs him back, her cheek pressed against the soft purple cashmere of his sweater.

She closes her eyes and breathes deeply, takes in the lingering scent of his cologne and coffee, the stronger smell of chocolate clinging to his clothes from the hot cocoa they've been drinking. She feels a prickling at the back of her eyes, and she blinks to stop the tears that are threatening to fall.

After a few moments, and one deep breath that has Kate's entire body sagging against him, Castle loosens his grip. He's blinking when he steps back, and Kate can see the gleaming in his eyes.

"Hey," she says, reaching out to touch his elbow. "I'm okay, Rick. Thanks to you. If you hadn't called…" She trails off, mind wandering to the possibilities. If Castle hadn't called, if he hadn't figured out that Conrad had been framed, if he hadn't been there to help her out of her apartment…

"Kate." His hand rises to cup her cheek, his touch soft on her skin. "I wish I'd figured it out sooner, maybe saved your apartment."

She's shaking her head before he even finishes his sentence. "No. Don't. I...we're not exactly new to life or death situations." She smiles when he chuckles and covers his hand with hers, squeezes his fingers. "I'm just glad we're both okay."

"Me too." Their eyes lock, and Kate sees his darken and flick to her lips. "Kate…" he whispers after a long moment. "If I'd lost you..."

She should go to bed. She should say goodnight again, should retreat upstairs to the guest room. But she can't unwrap her fingers from his, can't bear to step away from him.

His fingers tighten around hers and he takes a step closer, tilts her chin up.

He seems to be moving in slow motion. Kate cranes her neck towards him, lifts to her toes, and when her lips meet his, she loops her arms around his neck.

The moan she hears must come from her, because Castle chuckles into her mouth and traces the seam of her lips with his tongue. She opens and meets his tongue with hers, testing, tasting. Her fingers play with the soft hairs at the nape of his neck, holding him in place, as his drop to her waist.

She doesn't want to stop kissing him; since turning him down after their first case, part of her has wondered what it would have been like, what he'd be like. And if this kiss is any indication, she thinks as he nips at her bottom lip, she wouldn't regret it one bit.

Desire blooms deep in her belly and she feels her blood hum with arousal. Somewhere in her consciousness she feels him nudge her backwards, and she grunts when her backside hits the metal banisters of the stairwell. She tears her mouth from his when his leg slips between hers, and she has to stop herself from grinding down on his thigh.

"Castle," she gasps, leaning as far back as she can, trying to put space between them. She wants him; it's been awhile since she's been with someone, and the simmering attraction she's felt for Castle since the start of their partnership is starting to boil over.

But not tonight. Not when an obsessed serial killer is still out there, gunning for her. Not when his daughter is just upstairs.

Castle gazes at her beneath hooded eyelids, his pupils dark with arousal. "Kate…" It comes out as something between a moan and a groan, and it takes all of her willpower not to say fuck it and just drag him to his bedroom.

"Not right now," she assures him, her hands coming around to cup his cheeks. "Later."

"Later tonight?"

"After the case."

His eyes narrow. "You were kicked off the case."

She raises an eyebrow, but it's hard to keep the smile off her face. "I know, but the killer is still out there." Her thumb brushes against the dark circle beneath his eye. "When the case is done, we can talk?"

Castle licks his lips and glances at her mouth again, but when his eyes meet hers the dark arousal is replaced with something else, something more fierce. "Them still being out there is reason to talk now," he argues. "I almost lost you last night, Kate. You almost died. And I would've never-" His voice cracks with emotion, and his fingers tighten at her waist. "Life's too short to put off something like this."

Kate surges into him, mouth clashing with his, fingers curling around his ears. She pushes him backwards, following, but when he stumbles and almost falls she pulls away with a chuckle. "Maybe you should watch where you're going?" she teases.

"Funny." He takes her hand and leads her to the bedroom, and she pauses inside the threshold, takes stock of the room she'd only gotten glimpses of before. He turns when she drops his hand, and he steps back to her, reaches up to cup her jaw. "Everything okay?"

She tears her eyes from his bed and finds him looking at her, concern in his gaze. "Yeah. I'm just…" She takes a deep breath. "It's a little overwhelming."

He brushes his thumb across the ridge of her cheekbone. "It's been a helluva day."

"Helluva day," she repeats with a shake of her head. It has been a long day, and she's been fueled by caffeine and adrenaline through most of it. But she hasn't had coffee for a few hours, and the adrenaline is fading fast. All of a sudden she's tired, so tired, and while she wants to take the man in front of her to bed, her legs are about to give out on her.

"I know what I said about life being too short, but you're exhausted, Kate." Castle drops his hand to hers and squeezes, presses a kiss to her cheek. "Don't move."

She does move, but only to turn her head so she can watch him. He disappears up the stairs, returns in a few moments with her duffel bag in hand. "Castle-"

"Just to sleep." He sets the bag on an armchair in the corner, then returns to her side. "I'll let you get ready in peace. Do you need anything? Toothbrush? Face wash?"

Kate can't keep herself from bracketing his face with her hands, and lifting to smudge a kiss to his mouth. "Thank you," she whispers against his mouth, and she feels his smile against hers.

"It's a little selfish," he admits, a flush rising to his cheeks. "If I wake up because I dream that I was too late, I don't want to have to go upstairs to make sure you're alive."

"Oh…" Kate breathes, and kisses him again. She keeps it soft, but tries to pour her gratitude into the press of her lips. This man, this sweet, caring man...he can be a jackass, but how could she ever think that was all he was? "Thank you. I won't be long."

She keeps her word, clearing her face of makeup and brushing her teeth before rummaging through her bag. Where are her paja-

Oh. Right.

All of her clothes are on their way to the dry cleaner.

"Um, Castle?" she calls out, cracking the door open.

He's in front of her in an instant. "Yeah, do you need something?"

She feels her face flush and ducks her head, wishing she'd taken her hair down already so it would hide her face. "I don't have any sleep wear."

"You don't need sleep wear," he teases in a low voice, his eyes darkening as they sweep down her body.

Kate crosses her arms over her chest and raises an eyebrow. "Castle. Do you think Alexis will let me borrow something?"

"She's probably asleep, and you're too tall anyway." Castle disappears for a few moments, and Kate hears the sound of dresser drawers sliding open and shut. "Sorry, I know they're too big," he says when he returns, something red in his hand.

Kate takes the clothes with a grateful smile. "Thanks. I'm sure they'll be fine." In the end, she has to roll the waistband of the boxers over a few times, but she manages to get them to stay on her hips. Not like Castle would mind if they slipped off, she's sure, but she'd like to remain at least partly decent since his daughter is just upstairs.

Deeming herself appropriate after one more once-over in the mirror, she nods at her reflection, slips her toiletries back in her bag, and opens the door.

Castle had changed while she was in the bathroom, and he's perched on the end of the bed in sweats and a simple black t-shirt. He looks up when she steps back into the bedroom, and his face lights up when he sees her. "You look good in my clothes," he says, his gaze traveling down her body. "But I'd much rather see you out of them."

Kate smiles despite the eye roll she gives him and drops her bag next to the dresser. "Do you have a side?" she asks, kneeling and rummaging through her bag for her phone charger.

"No." He grabs her arm when she stands and steps closer to him, and tugs, causing her to stumble to the bed next to him.

She has to brace herself on his shoulder when she falls, and her other hand comes up to his shoulder. "Any preference?"

Castle smirks at her. "In the middle, with you under me?"

Kate feels her face flush at his words, and she finds she doesn't mind the thought of that as much as she once thought she would. No, she likes it. She likes it very much. "Left or right?"

"I really don't care, Kate." He kisses her, a swipe of his tongue across hers heating her blood again. "Make yourself comfortable. I'll be back in a few."

After a few moments of indecision, she decides on the left side, and plugs her phone in before climbing under the covers and propping herself against the headboard. She sees the bathroom door open out of the corner of her eye and lifts her head at the sound of footsteps, footsteps that abruptly stop.

Castle clears his throat before finishing his approach to the bed, matching her position at the headboard. "I could get used to this," he admits at Kate's questioning look, then his eyes immediately widen. "Did I say that out loud?"

"I'm afraid so." It's too easy, he's too easy, and when Castle's shoulders slump, she finds his thigh under the covers and pats it. "Thank you. For everything." She presses a kiss to his cheek, then lies down. "Good night, Castle."

"Until tomorrow, Kate."

Prompt from the Castlefanfics prompts blog, submitted by bunysliper: "In Boom, when Beckett gets to her feet to go to bed, Castle catches her hand and tugs her back to kiss her." It's not exact, but hopefully it's alright! As always, thanks to Callie for the beta.