They had to do high ropes today. He had to climb up to some height that would no doubt terrify him and his only pillar of support was solely responsible for his inability to focus this morning. He was going to die. He was pretty sure of it. All thanks to Kate Beckett and the sound of her moaning playing on repeat in his head.

"Hey," Beckett says, sliding up next to him, bouncing on her toes.

He drinks her in. Her long, toned legs staring back up at him from beneath those damn shorts that look way shorter than they did to him yesterday. Castle wants those legs wrapped around him. He wants her heels to dig into his back as he –

"You okay, Castle?"

His eyes shift upward toward hers. "No. No, I'm not okay."

He kept quiet last night, pretending to be engrossed in some book by the time she made it back to their cabin. Quite frankly he has no idea what he was reading because the only thing he could focus on was her. And if he's going to go climbing toward his death this afternoon, they need to talk about this.

"I heard you last night," Castle tells her, dropping his voice. "In the shower."

Her face reddens and she shifts her gaze so she's looking at anyone but him.

"You're driving me insane, Beckett. I…I need to touch you."

Her breathing becomes shallow. "So then touch me."

She keeps her eyes trained on Jared as he explains their first warm up activity, but she moves closer to Castle in invitation. His hand slips around her back, dancing around the waistband of her shorts. He feels her lean into his touch. He needs more; he can't do this here.

"Pretend you got stung by a bee," Castle whispers.

"What?" she whispers back.

"Just do it."

Beckett yelps, jumping away from him.

"Son of a bitch," she curses.

"Is there a problem?" Jared asks, starting to head in their direction.

"Bee sting," Castle tells him. "I'll take her to first aid and help her out. You guys go ahead and start. We'll be right back."

Jared nods, turning back to the rest of the squad as Castle grabs Beckett's wrist and pulls her in the direction of the first aid cabin.

"I just bought us a few minutes," he says, pushing open the door and making sure the coast is clear.

"A few minutes for what?" she asks, trailing in behind him.

"For me to touch you."

She bites her lower lip, her eyes growing dark and hooded, and that does it for him. His mouth is on hers in seconds, backing her up against the table. They're both fighting for dominance in the kiss, both of them trying to get the upper hand. Castle tangles one of his hands at the base of her ponytail and gets her to make that same little moan she made the first time he kissed her. This spurs him on further, and he lifts her so she's sitting on the table. She finally lets him take over, opening her mouth to him so he can explore and re-memorize what she tastes like.

As he keeps kissing her, her knees fall open, inviting him into the vee of her legs. Castle presses closer to her and her legs wrap around his hips just like he had envisioned this morning. He drags one of his hands up the bare expanse of her thigh, drawing another moan from her lips.

Beckett shifts her hips against his and nearly gasps when she feels his erection press against her. Castle breaks the kiss to trail his mouth down the bare, inviting, skin of her neck. He guides her head to the side by gently tugging on her ponytail and she obliges. She clings to him as he sucks at her neck and rotates his hips into her, making the most amazing mewling sounds.

She curses, her hips lifting off the table to connect with his as Castle brings his mouth back to hers. He couldn't believe he was dry humping Kate Beckett on the table of a first aid station like some horny teenager. She deserved better than this. But if those noises she's making are any indication, she had no complaints.

He drags his tongue down the other side of her neck, nipping at her earlobe.

"Castle, I –"

She doesn't finish as her mouth gets stuck in a silent scream as her orgasm hits her. He just made her come with of all their clothes still on. Holy hell.

Castle presses his forehead into hers, waiting for her to finish riding it out. Her hips twitch again before she breathes out a sigh of relief. Her hands come up to cup his face.

"What was that?" she breathes.

"I think it was an orgasm. I'll explain how that works later."

She bats his chest, rolling her eyes. "Not what I meant."

"Sounded like what you meant."

"You're still hard," she says, her eyes dropping down to the bulge in his pants.

He shrugs. "Have been all weekend."

"Let me help."

She reaches for the zipper on his shorts, stroking him through the fabric with her other hand.

"Beckett –"

"You were almost there," she says, pulling him out of his boxers. "I could tell by the way you were grunting."

"How do you know what my sex noises sound like?" Castle groans, as she runs her thumb over his tip.

"I know what men sound like. I've brought enough of them close to the edge to know."

"Can you not talk about other men while you're doing that?"

She chuckles, kneeling and dipping her head to draw him into her mouth. Fuck. Fuck. Her mouth is on him. Kate Beckett has his dick in her mouth. Castle fists his hand into her ponytail again and looks down at her. She's staring back up at him, doing this amazing thing with her tongue.

His eyes slam shut and his hips shoot forward. She was right, he was close. He comes in her mouth, instantly wishing he could have warned her it was about to happen. But Beckett straightens up grinning, wiping him from the corners of her lips. She swallowed.

How the fuck did he end up here with her of all people? How the hell is he this lucky?

"We should get back," Beckett says, looking over her shoulder. "I think you managed to get the stinger out by now."

"Kate."

She spins back to look at him, watching him tuck himself back in his pants.

"Has anyone ever told you how incredible you are?"

She smiles, lacing her fingers through his and squeezing. "Not lately. But it's always nice to hear it."

"So how's that bee sting doing?" Esposito asks as they head toward the high ropes course.

"It's better," Beckett responds, trying to hide her smile.

"And where'd it get you, your back?" Ryan asks.

She and Castle both nod.

"Interesting, so then what's that on your neck?" Ryan asks.

"Looks like a hickey," Esposito grins.

Beckett's eyes widen and her hand flies up to her neck.

"Some treatment plan you got going there, Castle," Esposito says as he starts to walk ahead. "Remind me not to ask for your help if I ever get stung."

Ryan laughs and starts to walk ahead too.

"We are so busted," Beckett groans, her hand still rubbing at her neck.

"We could always just pretend that it was aliens again."

She groans again, rolling her eyes. "Nice try, Castle. But aliens don't exist anymore now, than they did during that case."

He mumbles something incoherent as they keep walking along. Her arm brushes up against his as the high ropes course comes into view.

"Are you ready for this?" she asks.

"I trust you," Castle tells her as they keep walking. "So yeah. I'm ready."

He feels like he's making an ass of himself as he tries to climb the ladder to the first platform. This first part isn't even that high, but he's got himself all worked up about it, already afraid to chance a glance at the ground. For a guy who likes to hang out on the rooftops of buildings, you're being a big wuss. Castle keeps repeating that to himself because for some reason it seems to help.

"Would it help if you let me climb up there first?" Beckett calls from somewhere below him.

"No," he calls back. "Because then I'd be staring at your ass and I don't need that distraction right now."

He hears her laugh, lets his mind focus on that instead of the climbing, and finally makes it to the top.

"Hey, even Superman had his Kryptonite," Castle says when she makes it to the top, still laughing at him.

"I'm not laughing at you," she says, placing a hand on his arm. "Fear of heights is a pretty natural occurrence within the population."

"What are you the fact police?" he grumbles.

"No, just the regular police."

Castle throws her a look and she smirks, reaching out to attach the zip line clasp to her harness. His hands snake around her waist and hold her back to his chest.

"You realize you can't hold on to me and zip across, right?" Beckett asks. "You have to go on your own."

"I know."

"So then?"

"Didn't want you to fall."

"Thank you, but I'm good to go now."

Castle shakes his head. "No, I think we should just stay here. It's safe here."

"Castle, the faster we get through this course, the faster we can go back to our cabin and…play."

He raises an eyebrow at her. "On twin beds?"

"So we do some redecorating." She spins in his arms the best she can while still being hooked to the zip line. "Or we use them as twins and just get really intimate."

He lets go of her and steps out of her way. "Go. Be free. We have things to do; we don't have time for this."

She grins at him as she double checks her helmet and steps up to the edge. "Think about that as we go through this. It'll help with the height thing."

"What height thing?"

Beckett rolls her eyes and pushes off into the canopy of trees, ready for the day to be done so she can have him alone and all to herself.

"Took you long enough," Beckett mutters when Castle finally walks into their cabin that night without looking up from her book.

"We were doing man things, Beckett," he tells her, kicking off his shoes by the door. "I couldn't very well let them do it alone."

"But you'd let me do myself alone?"

He stares at her in confusion and she smirks and wiggles her fingers at him.

His face falls. "You started without me?"

"No," she laughs, slipping her bookmark into her book and sliding it under the bed. "But I was about ready to."

"What, the orgasm I gave you this afternoon and the one you gave yourself last night not good enough for you?"

He pulls his T-shirt off over his head and sits on the edge of her bed.

"Only if that PG-13 session we had earlier wasn't good enough for you," she says, her fingers hooking into the waistband of his shorts.

"PG-13? Wouldn't that blowjob make it at least R?"

"Does it matter? I'm just ready for the NC-17 version."

Castle grins and tugs at her tank top. "I like the sound of that."

He draws her mouth in for a kiss, his hands sliding up underneath the back of her top.

"You already took your bra off," he huffs, when his hands touch nothing but bare skin. "I was so looking forward to doing that."

"Guess that means we'll just have to do this again," she smirks, lifting her arms above her head so he can free her of the tank.

"I like the way you think."

He grabs the bottom of the tank and lifts it up, pulling it over her head and tossing it to the floor. His hands cup her breasts, his thumbs rubbing over her peaked nipples. Beckett arches her back, pushing herself further into his palms.

"Someone's eager," he teases, leaning forward to kiss the hickey on her neck he left earlier.

Castle's hands travel south, skimming along her stomach, until he reaches the waistband of her sleep shorts. He hooks his fingers over the edges and pulls, discarding them to the floor as well. He still can't get over the fact that this is happening. That Beckett is lying before him naked and waiting, her hair fanned out on the pillow like some kind of goddess.

"Tell me what you want, Kate."

He loves the way her breath catches when he uses her first name. It's like saying it, calling her that, is an intimate act within itself.

"I want your mouth on me. And I don't want to fake it."

He grins, sliding down so his mouth is hovering over her heat. He kisses his way up her inner right thigh, and then repeats the action on the left. She mewls as he does this, her hips twitching, seeking his mouth. He can tell just by looking at her that she's already wet, her need for him turning him on even more.

Castle swipes his fingers over her swollen nub, before he repeats the action with his tongue. He drags the flat of his tongue upward slowly over and over, until she starts making the most amazing noises. Then he starts licking at her faster, alternating with sucking at her clit. She moans, her hands reaching out to tangle in his hair, as he snakes one hand up to grope at her breast.

He curls two fingers of his other hand inside of her, stroking at her G spot as he continues to work her over with his mouth. Beckett starts to squirm under his touch, his name followed by curse words spilling from her mouth. Her thighs are starting to shake and he knows she's close, so he starts pumping his fingers inside of her faster and focusing his mouth solely on sucking at her clit.

She comes fast and hard, her body shaking from the release. Castle props himself up with his elbows on her stomach, his tongue snaking out to capture her juices from the corner of his mouth.

"Something tells me you weren't faking that," he smirks.

"Fuck," she mutters, her hands already yanking on his shorts.

He laughs and stands up to free himself from the rest of his clothing before he lies back on top of her.

"Aren't you going to ask me what I want?" he husks into her ear.

"And what is it that you want, Castle?" Beckett asks, her nails already scraping over his back.

"I want to be inside of you. And I don't want to fake it either."

She grins. "Shouldn't be a problem."

She grips his waist with her knees and flips them so she's on top.

"I like a woman who knows what she wants," Castle growls, his hands gripping onto her hips.

"Well then, you're going to love me."

Beckett takes him in her hand and slowly settles herself down on top of him. She takes him in fully, sighing at the way he fills her. She twists her hips around him, lifting up until only his tip is inside of her, before she sinks down on him again. Castle moans, his hands now cupping her ass.

But there's only so much of this slow torture he can take and he sits up a little, so she's more in his lap instead of full out straddling him. He pins her arms behind her back and starts thrusting up into her. She lets out a startled gasp at the change in dominance, but soon her back his arching and her head is rolling back in pleasure. Castle takes her arching toward him as an invitation, and draws one of her breasts into his mouth. She moans, rocking her hips against him harder.

He lets go of her pinned arms and flips her so she's on her back again and he can get better leverage. He brackets her head with his arms, as he picks up his rhythm and moves harder and faster. Her hands roam over his back, memorizing each plane of it. Castle draws up one of her legs and lifts it over his shoulder, giving him an impossibly deeper angle to drive into her at. His hand traces her skin down her stomach until it lands on her clit where he starts rubbing tight circles.

She screams his name, breaking apart for him again. Watching her come for him like that is the extra boost he needs to come undone himself. He keeps thrusting into her sloppily until he finishes, her name a whisper on his lips.

Castle starts to roll off to her side, but then he remembers the bed is only a twin and he'd roll to the floor if he did that. So instead, he flips them again so she can lie on top of him instead of the other way around. Beckett settles in against him, burying her head in the crook of his neck.

"You gonna tell me what it is we're doing yet?" Castle asks, threading his hand through her hair.

"I could be wrong, but I think we might be dating."

"Does this mean our days as a crime fighting duo are over?"

"Maybe not," she says, starting to trace shapes into his chest. "Montgomery seems to have a soft spot for you."

He laughs, his other hand skimming up her back.

"How long do you think it would have taken us to get to this point without this weekend?" he asks.

Beckett hums. "I don't know. Without all these trust exercises that call for all of the physical contact…"

He laughs again. "I think we made them more physical than they needed to be."

She shrugs, snuggling closer. "I'm just glad that we made it here. Wherever here is."

"You called it dating, remember?"

"Ah right yes, dating. You going to buy me dinner when we get back to the city?"

"Of course. Especially if we get to do this afterwards."

She places a kiss to his jaw, her lips turning upwards into a smile. "Oh yes, this will definitely be happening again. Because you, unlike some people, most definitely know what you're doing."

Castle smiles, his fingers continuing to dance across her back. "Oh my dear, Beckett. This was only the beginning."

AN: A huge thank you to everyone who has supported this story! Keep an eye out for a sequel entitled "Sin" that I hope to get out to you either later this month or by September. In the meantime you can follow me on tumblr, URL: tvfanatic, where I'm always answering prompts.