A/N: Takes place some time during the beginning of season 5, but nowhere specific. Just a little fun :)

She's had four cups of coffee and a bottle of 5 Hour Energy when she comes bounding through Castle's front door at three in the morning. Hopping through his living room, her shoes come off, jacket shrugged and tossed onto the couch as she tries to release some of the energy surging through her body. She is incapable of only walking as her scarf clears her head, lands somewhere on his desk, and then she's standing in the doorway to his bedroom, eyes wide and bright, lip pulled tight between smiling teeth as she takes in the quietly sleeping Castle, a still lump under his piles of blankets.

She wants loud, awake.

He actually squeaks when she strides up to the bed, pushing him onto his back and straddling him with a hop and a jump and no pretense.

"Beckett?" he asks, sleepily alarmed, voice clogged with unconsciousness still, but she'll fix that. She's awake enough for the both of them combined.

"Castle wake up, let's have sex," she breathes into his mouth, pressing her wide smile against his lips as her hips cradle his through the blankets. She's all frenetic energy, pushing down the blanket as she pushes up the hem of his tshirt, her freezing cold hands sliding up his broad chest.

He squeaks even louder at that.

"Ah! Cold! Cold hands, what are you – "

"I'm trying to take your clothes off, can you help me?"

He grimaces as his shirt rides up precious few more inches, nudging at his chin.

"But it's cold out there." He's pouting and she's rolling her eyes.

"I'll warm you up, Castle." The wink she throws him couples with a deliberate roll of her hips, and she can feel him warming up in other places, but his eyes are still sleepy, an adorable pillow crease cutting across his cheek.

"I thought you were going to be doing paperwork all night?" he asks absently as one of his hands sneaks out from under the warm cover of his blanket to trail up her trouser covered thigh.

"I accidentally ingested a lot of caffeine, I couldn't sit at my desk anymore."

He looks confused, she basically drinks caffeine for a living, but it's just the right time of night when too much can make a person jittery and burning for a release.

He's her favorite release.

She watches him come more awake as she starts quickly slipping the buttons of her own shirt through their holes, pulling the two sides apart quickly and tugging it off, letting it go where it will over the side of his bed. Her chest is heaving, hips rolling absently as she reaches behind herself to release the clasp on her bra, letting it go with a sigh of relief.

"Aren't you cold?" he whispers absently to her chest, making her purse her lips because even half asleep Castle is still Castle the man, and he is ever distracted by her naked breasts and a bad boob joke.

She's got him though, so she works with it, leaning her torso over him teasingly as she drops her mouth to his ear. "I'm hot, Castle." He groans as she starts shoving down his blankets again. "God, why do you sleep with so many of these?"

He's incensed as she bullies away the offending piles of cotton and down stuffing. "You don't usually complain when you're laying under them."

"Yeah well I'm not usually trying to fuck you through them."

As the words tumble from her mouth, he finally engages, shoving a hand into the back of her hair, cupping her head as his tongue swipes out at her lips.

Finally.

The blankets are away after that, gone somewhere near the foot of the bed as she crawls up and over them, presses her keyed up body flush against the soft material of his flannel pajama bottoms. He's not so soft though, under them, as her hand sneaks through the opening at the front, making him hiss and arch into her.

"Ready to play now?" she grins against his mouth, releasing him as she rises up onto her knees and unbuttons her pants, shoving them down as she reaches up a hand to his headboard to steady herself. As she toes them off, Castle's hands bracket her waist, mouth pressing against the bare part of her stomach looming in front of his face, making her arch into him.

She'll take that as a yes.

As her pants hit the floor, he doesn't let go of her waist, instead tugging her closer, mouth landing low on her abdomen, making her smile, but she's way too keyed up for what he's offering. Instead, she angles away, face dropping to meet his as she cradles his cheeks between her palms and kisses him deeply, her sloppy tongue leaving them both groaning.

"What exactly did you drink?" he asks as she removes her hands from his face, wrapping them around his own on her waist and tugging them up and over his head as he slides down underneath her completely. She pins him there, his crossed wrists underneath one of her palms as she settles over his lap, using her other hand to push his pants off just far enough to be out of the way.

"Four cups of coffee and a 5 Hour Energy."

"Jesus, Kate."

She just shrugs, using her free hand to toss her hair to one side, and then presses it palm down all the way down his body until she's got him where she wants him.

"Think you can keep up?"

She raises an eyebrow as she sinks down onto him, smooth and hot, her muscles all bunched and ready to strike. She needs to move, and so she does, using the palm she's got holding him down give her leverage as she raises over him and then sinks again, raises and sinks, hips twisting forward every time she comes down. She has to work for it in this position, thighs and knees straining as she does all the work, and it's exactly what she needs, what she wants, to feel that burn of muscle while the sweet jolt of arousal swirls in her gut.

"Why did you drink so much coffee so late?" he asks, staring at her as she rises over him, entirely too coherent for what they're doing. He hates being so passive though, instead engaging her with his words.

She releases his hands, moves both of hers to the sides of his head, bracing herself just over his face as she rides him tightly. "I was bored when you left," she breathes against his mouth, capturing his lips quickly, panting too hard to kiss him properly.

Her admission hits him, she can feel it shiver through his skin, that she misses him when he's not around. She makes a mental note to tell him more often, he has such a fragile ego.

He stops being passive then, using his newly freed hands to grip her waist, his own hips rising up to meet her on every down stroke, face buried in the side of her neck as she grinds and grinds until she feels it overtaking her. It's so quick though, her orgasm ripping through her with a force that makes her groan aloud, but he doesn't follow her, just sucks his way up her throat and to her ear, tucking her hair messily out of his way.

"Bored now?" he husks against her as she heaves, the slickness between them almost obscene now, but she keeps moving, soft little rolls of her hips and he helps, still hard inside of her.

"No."

She's breathing into his hair as she feels him shift under her, and so she kisses her way across his cheek until she reaches his nose, their foreheads resting together, eyes open and bright.

"You'll never sleep after just one round," he explains, bucking his hips up gently and smiling knowingly at her. She wonders how hard it was for him not to finish with her.

"You're sweet," she blurts as a sudden wave of affection hits her, this stupid, thoughtful man caught between her legs, forever thinking of her.

"Mm, sweet because I want to have as much sex with you as possible right now?" He's mumbling as he nuzzles back into her neck, his hips rolling up experimentally, waiting for her to be ready.

"And you ruined it. "

He cuts off her imminent eye roll as he flips them over, pinning her underneath him as he kicks his pants off the rest of the way.

"I thought you were sleepy."

He hums noncommittally into her neck, his hips thrusting against her finally, making her claw at his back. "I think some of your 5 Hour Energy got into my mouth."

"Into your mouth, huh?"

She can feel him grinning against her skin, hips picking up a rhythm as she gasps, extra sensitive from before, but she needs to move, wants to completely lose herself in him and the delicious haze of lust and caffeine she's got swirling through her blood.

"Harder, Castle," she begs him, leg muscles tight and rigid as she struggles against the friction she needs, but he's getting sloppy, out of control, so she pulls at his hand, shoving it between their bodies until his slick thumb finds her hard little clit and drags her back down under his blanket of lust with a hard shiver and a sharp bow of her spine.

He finishes just as hard as she does, collapsing down over her as he chokes down air, back tight with restraint and then loosening as pleasure works its way through him underneath her fingertips.

"That take the edge off?" he asks as he rolls over, pulling her with him until they're both lying on his pillow, sweaty and boneless. He yawns loudly as she drags his blankets back up from the bottom of the bed with her foot.

"Yeah, thanks Castle." She presses a kiss to his cheek as his eyes slide closed, her other hand cupping his face as she does, holding him against her nose as she feels him falling asleep.

Her body is worked and relaxed, muscles throbbing pleasantly as she presses against Castle's side, but her brain is still much too wired to sleep. Instead, she props her cheek on her own hand, elbow settling into the crook between their pillows, fingers rising from his cheek to the edges of his hair, brushing it softly as she watches him.

Coffee and Castle, she thinks to herself, smiling.

All she really needs.