A/N: didn't get much of a response to the last chapter..hope it was okay and you're all still enjoying the story.

Please note: it has now changed to M, but it's not turning into smut! It's only a small portion of this chapter, which I shall outline if you want to skip it and it's not going to be every chapter.

"What is it?" Kate asked, seeing the way Castle was staring at his cell. "Castle, what's wrong?"

"It's uh..Smith. You know, Montgomery's friend I told you about?" He winced at his own words, remembering how scared he'd been about telling her and how angry she'd been. They'd only just worked that out and here he was, bringing it up again.

"Oh," Kate said simply. "Well are you gonna answer it or just stare at it?"

"No, I'm gonna answer it. You uh..wanna listen?"

She was about to give him some smart ass remark about it being fairly damn obvious that she wanted to listen but she stopped herself. It had been hard for him to come clean and admit what he'd been hiding from her and the fact that he was openly asking if she wanted in on it now was massive progress.

"Yeah, if you don't mind," she smiled.

"Not a problem," he said, answering the call. "What the hell is going on? Why did they break into Montgomery's apartment?"

Smith's voice came across the speaker that Castle had turned on so that Beckett could hear too. "Oh most likely it's a clean up job. Making sure that Montgomery had nothing else incriminating in his files. As long as Beckett drops her investigation, we still hold all the cards."

Castle looked to Beckett, knowing full well Smiths words would make her angry. He held a finger up to her lips to prevent her from saying anything before he replied. "She's already on to our shooter. She's not gonna let go." Beckett was going to kill him. Talking about her as if she wasn't here, as if he was still doing all of this behind her back.

"Then we have a problem," Smith shot back. "If she doesn't stop, they will retaliate. I can't control the situation if you can't control her."

Luckily Smith had hung up before Kate began her outburst. "Control me? I'm not some wild animal that needs to be tamed, Castle! Who does he think he is? Talking like that..god, why the hell did you even do this in the first place?"

"Kate, please," Castle pleaded. "Calm down-"

"Calm down! You want me to calm down? That man you've been having secret phone calls and rendezvous' with has just told you that you have to control me and you want me to be calm about it? How many times do I have to tell you that I don't need anyone to protect me? I'm a homicide Detective, Castle, and a damn good one at that. I'm not some helpless woman who can't look after herself!"

"I know all of that, Kate," Castle replied exasperatedly. "And I'll admit, his choice of words was not very..suitable shall we say, but you have to understand I just want to protect you!" He thought they were over this, they'd had pretty much the same argument when he'd told her about Smith but here they were, rehashing it all again. "And I know you don't need or want anyone to protect but tough. I love you, Kate and I'm sorry, but I'm not going to sit here and let something happen to you, not when I could have tried to prevent it."

"You're playing the 'I love you' card now?" She asked incredulously. "Seriously? Didn't think you'd ever stoop that low Castle."

"Don't you dare make me feel bad for telling you how I feel," he growled. "Yes, I'm using that card now and yes, it might be low of me, but like I said - not gonna sit here and let them get you, so you might as well deal with it."

"Deal with it?" They were both stood up now, facing each other in the sitting room as they continued their argument. "What if it was the other way round, hey? What if they were after you and I was the one making secret deals for your life? Would you be fine with me doing that, trying to protect you?"

"It's not the same thing, Kate-"

"The hell it's not!" She shouted back at him. "So tell me, what gives you the right to do this, listen to the words of a man neither of us know, a man who could quite easily be tricking you and making it a hell of a lot easier for this Lockwood guy? A man who could be behind my mothers murder?"

"It's not him, Beckett."

"Oh, so you know who's behind it then?" She said with a laugh, but he could tell it wasn't one born of humour. "Because unless you do, I can't see how you can know for sure that this Smith isn't behind it!"

"I just do, okay? Because I've had no reason to believe that he is doing anything other than tying to protect you. And I know you don't want to be protected, to feel like you're a burden to someone but I'd have thought even you would be grateful a complete stranger has done everything he could to help you."

Kate let out a deep sigh. She couldn't do this right now. She was angry with him and at this Smith guy and being here with him was so not helping. "I'm going home," she announced.

"The hell you are!" Castle retaliated and his tone stopped her in her tracks to the door.

"Castle, the last thing either of us needs right now is to keep going over and over this. Quite clearly we're not getting anywhere, so I think it'll be best if I just go home and we can cool off." She was proud if how reasonable she sounded, because it sure as hell wasn't how she felt. Walking the rest of the way across the loft, she reached the door and opened it, but Castle slammed it shut again before she could leave.

"You aren't going anywhere, Beckett." He said. "We have no idea who's out there waiting for you and I'll be damned if I let you leave here with that in mind!"

"Let me leave? Contrary to what Smith seems to think, you don't get to control me!" Jesus Christ she was so angry right now. "Now, I'm going to go-"

She was cut off from telling him she was leaving once again by his lips pressing against hers, hard and insistent. She resisted at first, not giving him anything in return but she couldn't keep that up for long. Parting her lips slightly, she allowed him access to her mouth and he didn't waste anytime, his tongue darting in to deepen the kiss. Not being able to hold back any longer, her hands trailed up to tangle in his hair as he pushed her back against the door, pressing his hips firmly into her lower stomach.

His hands went in opposite directions, one cupping her face and the other squeezing her backside. It was hard, fast and passionate..he'd never kissed her like this before and she never wanted it to end. It was exactly what she needed, what they both needed. He lightly bit her bottom lip and she gasped, her right leg climbing his thigh to wrap around his waist, drawing him as close as possible.

He drew back a few minutes..hours..later, both of them panting hard. Resting his forehead against hers, he grinned down at her and said, "still leaving, Beckett?"

Ass. "You're a complete ass, Richard Castle," she growled, trying to hide her grin. Leaving? Not on her life.

"You want me anyway," he replied cockily and she slapped his arm, pushing him off of her.

"No, I'm not leaving." She walked away from the door and back into the living room. "I'm still angry, but I'm not leaving."

"Ah, if you're still angry then maybe I wasn't doing it right.." He walked back towards her but she held up a hand to stop him.

"I don't think so, stud," she warned. "Don't think that just because we're together now that you can pull stunts like that and I'll forgive you."

"We can always take it to the bedroom.." He suggested and she took a deep breath to control herself.

"No," she said firmly, going against everything her body was screaming at her. "We're going to talk this out."

"Spoilsport," he grumbled and she laughed at him.

"God you're such a child! Do you have any ice cream?"

"I um..what..?"

"Ice cream, Castle," she repeated. "Do you have any?"

"Beckett, this is me you're talking to - of course I have ice cream. But uh..not twenty minutes ago we were fighting and now you want ice cream?"

"We were fighting? Mm, I guess we were!" She said, heading over to the kitchen and he followed feeling thoroughly confused. "Oo, our first fight! Did I win?"

"Who are you and what have you done with my girlfriend?" If he didn't know better, he'd think he was dreaming, the only thing that let him know this wasn't a dream was that Beckett was asking for ice cream and not naked in his bed. Simple things.

"Oh shut up," she laughed. "Yes, we had a fight. I said stuff I shouldn't have and you were trying to be all manly and protective. I said I was going to leave and you convinced me otherwise and now I want ice cream. Problem?"

"No," he replied quickly. If that's what it took to make up after a fight he'd make a point of pissing her off more often. "You want ice cream, I'll get you ice cream."

"Finally," she muttered. Five minutes later and they were back on the sofa, scoops of ice cream in their bowls, Castle still wondering what the hell had just happened. "So, we could sit here and spend hours talking about what we were just fighting about but I'm kinda sick of disagreeing with you so can we just get it over with please?"

"What, so you're admitting I'm right?" Worth a shot..

"Ha, you wish," she laughed. "No, what I meant was that I think it's obvious neither of us are going to agree on this-"

"No, we're not," he agreed. "So..we're agreeing to disagree?"

"Yeah, I guess," she conceded. "Look, Castle..I know you're just trying to look out for me and I know it's because you care about me but I don't need you to do that."

"Kate, I don't do it because I feel like I have to, I do it because I want to." He set his bowl on the coffee table and continued. "I have never, ever felt like this about anyone in my life. And I know you're scared but I am too..these feelings are so new to me and I guess I just want to do everything I can to make it work..make sure you're okay and that I can spend the rest of my life with you."

"Okay. So, as much as I don't feel like you need to look out for me, I've come to figure out you only do it because you care. And even though I might not like it, can we just agree to not talk about it? I'll just..pretend you're not constantly looking over my shoulder for me and you can..make it less obvious?"

"Of course, Beckett," he laughed, "if that's what you wanna do then that's what we'll do. But you need to remember why we got into that fight in the first place..Smith is right, you don't drop this and they're going to come after you."

"I know that, Castle. And maybe I'm making the biggest- one of the biggest mistakes of my life by not dropping it but please, don't you ever think I'm choosing this case over you, okay?"

"Why did you stop yourself and change what you were saying?" He asked.

She should have known he wouldn't let her slip past with that one. "Because the biggest mistake I've ever made is not telling you how I felt a hell of a lot sooner," she admitted. "But that's not the point right now. The point is that no matter how much this case means to me, how badly I want justice for my mom, I will always choose you, okay?"

He was feeling confused again. "So uh..why did we have that fight if you're just going to give in?"

"I'm not giving in," she replied defiantly. "I'm not dropping this, not now. They get too close, then maybe I will. But not right now, not when I've got the biggest lead in forever. So, can you meet me in the middle?" She asked. "You want me to drop it but I don't want to. So..can I keep going but carefully? I know what's at risk at the second it goes too far I promise you I will drop it all but please, Castle, don't make me drop this when I'm so close?"

It wasn't what he wanted but it looked like it was the best he was going to get. "Okay," he relented. "We'll meet in the middle. On one condition: you don't do anything without me, okay? I'm your partner, your best friend and now I'm your boyfriend, okay? So whatever we do, we do it together."

"Deal," she smiled. "Thank you, Castle. I promise I'm not going to do anything to ruin this..us, not ever."

"Good," he replied, pulling her into a tight hug. "I don't know what I'd do without you."

She pulled back a few minutes later and looked up at him. "Would you mind if I uh..invited Charlie over tonight?" She asked. "It's just I know what these people are capable of and I know they're probably not above going after her if they can't get to me. I guess I'll just feel a little happier knowing she's safe."

"I was just thinking the exact same thing," he laughed. "But uh, you do know you're pretty much doing to Charlie what I've been doing to you.."

"She's my sister, it's different," Kate grumbled, knowing it wasn't and he was right.

"It's not," he said, "not at all."

"Okay, it's not. You're right and I'm wrong, happy?" She frowned at him.

"Can I get that in writing?" He joked. He'd done it again. Whenever she was trying to be mad at him, he came out with some stupid remark that made her forget about being mad at him! God he was infuriating.

"Don't push it," she warned.

"Sorry," he said but she could tell he wasn't. Damn man-child.

"I'm going to call Charlie, won't be a sec.."

Castle watched her find her cell and begin the call with a smile on his face. Yes, they'd had their first proper fight as a couple but she hadn't run, he hadn't let her. And then she'd ironed it out so quickly and simply he couldn't believe it was the same person. He wasn't going to take it for granted though, he had a feeling that the only reason she had caved was because she knew he was right - he wasn't stupid enough to think he could solve it all with some heated make out sessions when he'd really messed up.

"Charlie is staying at Ethan's," Kate announced as she came back to the couch.

"Oh. Are you okay with that?"

"I'm her sister, not her mom," Kate laughed. "I don't really have a choice. I mean, I could tell her why I'm so worried and I know she'd be here in an instant but I don't want to scare her. We've been dealing with this for a lot longer than her, I'm sure she'll be fine."

"She will be," Castle reassured. "Mother is at the Hamptons house until tomorrow afternoon and Alexis is at Paige's - they're still fretting over their graduation speeches," he added, rolling his eyes.

"Castle, she graduates from high school in two days, it's a big deal!"

"Don't remind me, you're making me feel old," he grumbled.

"Well," she whispered seductively. "Want to make the most of having the place to ourselves and prove to me that you're not old?" His eyes followed her as she planted her lips on his neck, nipping and sucking lightly as her fingers started unbuttoning his shirt.

"Beckett," he whispered to no response. "Kate," he tried again.

"Castle," she snapped. "Will you shut up and take me to bed?"

His mouth latching onto hers was the answer she got.

Rolling over and glancing at the clock, Kate saw it was just after 2 in the morning. Rolling back onto her side facing Castle, she grinned. They certainly had made use of the loft being empty, not having to worry about how much noise they - well, Kate - were making.

"Thought you said staring was creepy," Castle laughed into the darkness.

"Sorry, did I wake you?" She asked.

"Don't think so, just woke up. Are you okay?"

"I'm fine, Castle. Better than fine, amazing, in fact."

"Good," he replied kissing the too of her head. "Me too."

(M RATED, FEEL FREE TO SKIP)

"Good enough to go for round 4?" She asked cheekily.

"Oh, so that's why you're awake is it?" He teased, reaching over to pull her onto his body, her legs resting on the bed either side of his hips.

"Well it wasn't," she grinned, wiggling her hips. "But it seems like I'm not the only one ready for round four.."

"God you're perfect," he breathed out, pulling his lips down to his.

She made quick work of removing his boxers, her hand slipping down to cup him as he groaned into her mouth. "Shit, stop that Beckett," he gasped as her fingers began teasing his length. "Or this is gonna be over way too soon."

"Having trouble controlling yourself, hey?" She teased, ripping her underwear off. His hand glided up her thigh, slipping between her legs and into her heat. "Jeez you're so wet," he groaned, "you're going to be the death of me woman!"

"It's all for you, Castle." She leaned down to speak into his ear, her voice husky with arousal. She should have known it would be like this. The first time had been incredible and so had the two after that. But then, after the four years of verbal foreplay, surely this was inevitable? That they'd be perfect together.

Reaching a hand down between them, she grasped him firmly and guided him into her, gasping as his filled her so perfectly. "Fuck, Castle," she breathed into his lips, "move, goddammit!"

He did as she instructed and she cried out, the sensations so much more intense with her on top. He was so deep inside of her, her hips thrusting to meet his..mouths fused together in a heated frenzy. This wasn't going to last long, she was too desperate for him. "Castle," she gasped, "I'm not going to..oh god, Castle," she cried when he took a pebbled nipple into his mouth and bit down lightly. "I'm so close, Castle.."

"Already?" He laughed. "God you're insatiable!" He joked but he was close too, the feeling of having her wrapped so tightly around him was almost too much to bare.

"Now, Castle," she called out, "oh god, please.." Who was he to deny a woman what she wanted? Fusing his lips to hers again, their kiss was as sloppy as the thrusts their hips were making, both of them struggling for breath as they neared their peak. "Shit..oh oh oh..please.." Kate begged and with one deep thrust, hitting that spot inside her that drove her crazy, she lost it. She clenched around him, her screams muffled by his mouth against hers. It was enough to drive him over the edge, his hands gripping her hips tightly as he came too.

Her head rested against his shoulder as they came back to earth, trying to get their breath back. "Oh my god," Kate panted. "That was amazing.."

"That's what you said the last three times," Castle laughed. "Is this how it's going to be, you constantly saying we're topped the time before?"

If you keep that up then yes," she replied, rolling off of him and curling into his side. "Remind me again why I fought this for so long?"

"I don't know but if the sex is that good every time then I don't think I care," he said and she laughed.

"Me either. God, it's never been that good, not with anyone." She'd had sex, and quite a lot of good sex but what she had with Castle..god, that was something completely different. It was mind-blowingly incredible, she couldn't imagine ever having enough.

"Never?" He questioned and she immediately regretted saying it. He could tell by the way the she stiffened against him that she hadn't meant to give that away. "Hey, don't freeze me out. It's never been like that for me, either."

"Really?"

"Yes, really. Just more proof that we're meant to be."

"You're such a sap, Castle."

"Only for you babe, only for you."

"Babe?"

"Yeah. Got a problem?"

"Nope, no problem," she grinned. Babe..she liked it. "Right, it's 3am..we need to sleep!"

"Well I still would have been asleep if some scorching hot brunette hadn't woken me up for sex," he grumbled.

"Shut up and go to sleep, Castle."

"Yep."

(END OF M)

Kate woke the next morning and stumbled bleary eyed into the shower, feeling a little sore. But in a good way..she couldn't remember the last time she'd felt like this after sex..but it was so worth it.

She managed to finish her shower without Castle interrupting her which was an achievement in itself, really. When she left the bathroom, he was only just waking up.

"What?" He whined, "don't tell me I missed shower time?"

"Yep. Sorry sleepyhead, showered without you."

"Fancy getting all hot and sweaty so you have to shower again?" He asked hopefully.

"Nope, gotta get going. We need to drop by my apartment and get clean clothes before we go into the precinct."

"Spoilsport," he moaned.

"Go shower, Castle," she grinned, "and quickly!" She added as he went into the bathroom.

An hour later and they'd both showered and dropped by Kate's apartment to grab fresh clothes. They arrived at the precinct only a little later than normal, but no one seemed to notice. Esposito and Ryan weren't in yet, she could only assume they were running down a lead on her shooter. She just hoped they'd done as she'd asked and not told Gates about their case.

While Castle was getting them coffee, she quickly called Charlie, seeing if her and Ethan wanted to meet them for lunch. Charlie agreed, saying she'd ask Ethan when he was off the phone and they arranged when and where to meet. Kate hung up the call just as Castle returned with their coffees.

"What do we do now?" Castle asked as he sat in his seat next to her desk.

"Guess we wait for Espo and- hey guys," she called out as the boys exited the elevator. "You got anything?"

"Yeah," Esposito began. "We found Maddox, well where he's staying, anyway. We searched his hotel room but he wasn't there."

"We found Montgomery's wedding album, though, and there was a picture missing," Ryan added.

"So..he's probably looking for Smith," Castle said to Beckett.

"Who?" Espo and Ryan asked in unison.

"You wanna explain or should I?" Castle asked.

"You do it," Beckett said, picking up her coffee. "You know it better than me."

Half an hour later and the boys had been filled in on what Castle and Beckett knew and agreed that Maddox was probably looking for Smith too. They didn't really have much else to go on, the four of them grouping around the murder board in a desperate attempt to find something they'd missed.

"Ugh, we're getting nowhere!" Beckett said a couple of hours later, "we need Maddox!"

"We'll head back over to his hotel, see if he's been back around," Espo said.

"And we're going to go and meet Charlie and Ethan," Castle said to Beckett. "Come on, it'll all still be here when we get back."

Kate agreed, thinking a break might do them some good. "Oh we're a bit late," Kate said, checking her watch as they walked into Remy's. They were supposed to meet twenty minutes ago.

"Well it looks like Charlie is late too," Castle said, scanning the room. "Come on, let's find a table."

"Her and Ethan probably took a late shower or something," Beckett grinned. She'd definitely be teasing Charlie when she got here.

"Yeah, because Ethan's girlfriend doesn't shower without him," Castle pouted.

"Be a good boy and I'll make it up to you tonight," Kate grinned and Castle stopped acting like a child.

"I'll hold you to that, Detective," Castle grinned as they sat down to wait for Charlie and Ethan.

"I'd be worried if you didn't," Beckett muttered. "Lets get coffee, they shouldn't be too long," she decided, calling a waitress over. "Well I hope not, I'm starving!"

"Worked up an appetite last night," Castle grinned and she blushed.

He had a point though, she must have burnt a hell of a lot of calories last night. "Shut up or you don't get a repeat performance tonight."

That kept him quiet.

A/N: woah, 4500 words - a lot longer than I planned! Hope I highlighted the M stuff well enough if you didn't want to read it! Reviews more than welcome :)

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