A/N: Happy CastleFanficMonday. Here's a little M rated Caskett to get you through this Castle-less Monday.

Disclaimer: I do not own Castle or the characters used in this story.

This is a prompt fill that was prompted to me on twitter by GeekerMom. Prompt will follow at the end. I didn't mark it complete because there will eventually be a second chapter.

Remedies

Castle frowns when his call goes straight to her voicemail. He knows Kate has the day off and three months into their budding relationship they try to spend as much of their free time together as possible. It's rare, days off with no interruptions and they try to take advantage of them.

He knows she's home so he directs his car service towards her apartment, shooting her a text that he's on his way.

After the third unanswered knock he's about to head back to the loft, but he can't help wondering where she would have gone without telling him. He's just taken a step toward the elevator when Kate swings the door open, shielding her eyes when the bright light from the hallway floods into her dark apartment.

"Kate, are you okay?" he asks, scanning the room behind her and frowning at the lack of light.

"Castle, get in here and shut the door, the light is too bright," she growls, shuffling away from the door to let him in.

He follows her, shutting the door quickly behind him. He thinks back on the previous night, trying to recall if she'd been drinking while they were talking on the phone. He would normally spend the night with her when he knows she has the next day off, but Alexis had planned a movie night for them and Kate insisted that he spend time with his daughter.

"It's almost noon, are you hung-over?" he asks, stepping closer to her so that he can see her face which is only illuminated by the small streak of sunlight that has escaped into the apartment through the small space between her curtains.

"I wasn't drinking last night, Rick. I have a horrible headache and the light makes it ten times worse."

He dusts a hand over her back, pulls her closer when she drops her pounding head to rest against his chest.

"That sounds worse than just a typical headache, Kate."

"Migraines," she states, sighing against his chest. "I was diagnosed with them when I was fifteen, but luckily I don't get them very often."

He rubs her back, fingers kneading into the knotted muscles between her shoulder blades and she moans her approval, pressing more heavily against him.

"Do you take medicine for them? I can go get you something if you don't have any," he offers, continuing to work her sore muscles.

"I already took some, it's not helping so far. I'm sorry I didn't call you, it always knocks me out after I take it."

Castle nudges her towards her bedroom, lifting her weight into his arms when she stumbles against him.

"Castle," she bats half-heartedly at his arm, but sinks against him when her head starts pounding violently again.

He lays her on the bed, making sure she's comfortable before climbing in beside her.

"I'm sorry. I know this puts a damper on spending the day together," she apologizes, pressing a kiss to his cheek when he rolls closer to her.

"You have nothing to apologize for, Kate. We are spending time together."

She sighs and pats his chest, a silent thank you for being the sweet, understanding man that he is.

"I'm not going to be much fun though, Babe. This headache is no joke."

He's quiet for a minute, suddenly remembering an article that he read once. He's not sure she'll go for it, but he's willing to do anything to help alleviate her of her headache. And it may not help, but maybe it will take her mind off of it for a while.

"What if we try something to get rid of the headache?" he suggests, holding his breath while he waits for her answer.

"I already took medicine, I don't think anything else is going to help."

"Are you willing to try something else?" he asks, trailing is hand down her side and toying with the hem of her robe.

"I'm not really up for sex right now. Lifting my head from the pillow is like torture."

"You don't have to do anything. I read an article that said orgasms can help relieve headaches. It's worth a try and I'm willing if you are."

She's quiet at first and he assumes that she's contemplating the idea, but her answer is evident when she unties her robe and pulls him in for a kiss.

He smirks against her lips when she pushes on his shoulders, nudging him down her body.

He pauses on his way down to pay equal attention to her breasts, flicking each hardened nipple with the tip of his tongue. She gasps but pushes on his shoulders again and he obeys, sliding further down the expanse of her body.

"Please, Castle. Make this damn headache go away."

He obliges her instantly, knowing it would be cruel to make her beg when she's feeling as bad as she is.

He groans when he finds her already bare and ready for him, almost as if she anticipated this moment.

Dipping his head between her legs he slides his tongue through her folds, hums in approval when he finds her wet even in her current state. Normally he would draw it out, alternate between sucking her clit and delving his tongue into her throbbing flesh, but his goal is to cure her headache as quickly as possible,.

He sucks her clit into his mouth just as he presses two fingers into her, her walls clenching around the intrusion as he starts immediately thrusting them in and out.

Kate moans, hands tangling in his hair to hold him there.

He continues to work her, tongue flicking rapidly over her clit as his fingers work her, pushing her closer to the edge of what he hopes will be a headache free bliss.

It's the fastest he's ever gotten her there, aside from the night she showed up soaking wet at his door and so ready for his touch that she broke apart the moment his fingers brushed over her.

She cries out a warning just before she breaks, the orgasm crashing over her with such force that she arches off the bed, sobbing his name through her release.

He works her down slowly, withdrawing his fingers only after her breathing has returned to normal, but when he kisses his way up her body she grips him tightly, pulling his body firmly against her.

"Kate?" he questions against her lips when she unbuttons his pants and starts pushing them down his legs.

"I still have a damn headache, Castle, but I want you inside me, right now."

He doesn't argue but he can't help feeling disappointed that his idea didn't take her headache away.

He kicks his pants and boxers off the bed, settling between her legs and dragging his erection through her slick folds.

"Now, please," she begs, using her legs to press him into her and crying out when he sinks all the way in.

His hips snap against hers as he thrusts in and out, and she clenches around him, hips arching off the bed.

"Harder," she demands, moaning her approval when he begins pounding into her, control snapping with each powerful thrust.

"Yes, yes, yes," she chants, spurring him on until the familiar coil swirls in her stomach.

Castle lifts her legs towards her chest, changing the angle and thrusting harder than he ever has.

"Ah, fuck. Yes, I'm almost there," she cries out, just as Castle's rhythm falters and his thrusts grow sloppy.

And when she falls over the edge into the abyss of ecstasy she takes him with her, moaning when the hot wash of his release fills her.

He rolls off her and collapses onto the bed, heart racing as he tries to get his breathing under control.

Kate stays quiet for a long time, so long that he thinks she's fallen asleep and he's thankful that at least she'll have relief from the headache when she sleeps, but then her voice cuts through the room and she rolls over, draping herself across his sated body.

"Mm, good idea, Castle."

He laughs, pulling her closer so that he can press a chaste kiss to her lips.

"Yeah, if only it helped the headache," he sighs, threading his fingers through her hair and massaging her scalp.

"What headache?" she asks, grinning into his mouth as she thoroughly thanks him for his headache remedy.

Prompt: "A horny Castle doing everything he can to alleviate Beckett's headache."

Would love to hear your thoughts! xo