A/N: Charlie and Castle will not be happening people! I've come up with an idea to help though, will work it in when I can!

I know some of you are just waiting for Caskett to happen, and I can promise you it will but I'm working up to it! Also, I'd just like to point out that I currently have no intention of stopping this story as soon as Caskett get together, I'm planning on continuing after that if you're still with me at that point :)

Little warning - gets a bit angsty towards the end of this chapter!

"...Kate, what haven't you told me about moms case?"

Kate's eyes widened in shock before narrowing them at Castle.

Oh crap, he thought, maybe she had forgiven him too soon.

"Castle.." She said, "what did you say?"

Castle didn't know what to do. He knew bringing up Johanna's case wouldn't end well, even if he had brought it up by accident. He had just kinda hoped that he wouldn't have been around when Charlie decided to question her sister but apparently, that wasn't happening.

"I um..I didn't say anything.." He replied, half truthfully. He hadn't really told Charlie anything, just that he had looked into the case and that she should talk to Kate about it, shouldn't be that much of a big deal, right?

"Oh, so it's just a coincidence that Charlie has come home, seen you as her reminder and asked what's going on?" Kate asked skeptically, she couldn't believe he'd brought it up with Charlie, she'd told him how happy she was to just have her sister back and how it had almost torn them apart when their mom had died and this was what he did?

Castle winced, when she put it like that, she had a pretty big point.. "Okay look, Charlie was saying that you'd forgive me for what I said earlier - and I said you'd forgiven me for worse, like the time I looked into your mothers case. Except I didn't exactly say that, I stopped myself but little miss interrogation over there got it out of me. All I said was that I looked into it and if she wanted to know anymore then she should ask you."

"Which I am," Charlie supplied helpfully.

If Beckett wasn't still pretty angry at all that Castle had done today, she would have laughed. She knew herself just how well Charlie could extract information people didn't think they'd ever admit. Still, none of this would be happening if Castle had kept his mouth shut in the first place.

It wasn't that she was against telling Charlie everything that had happened in the past few years, it was that she was worried about Charlie's reaction. She'd literally just got her sister back and now, thanks to Castle, that might not be lasting much longer, the last thing she wanted was for Charlie to fly off somewhere else but short of kidnapping her, Kate couldn't stop her.

"Maybe I should go.." Castle suggested tentatively, slowly edging his way towards the door.

"Richard Castle you take one more step towards that door and I swear to god I'm going to shoot you," Beckett warned with an icy glare that had Castle stopping any form of movement. "Why did you even bring it up in the first place?" She asked.

Castle didn't even have time to formulate an answer before Charlie jumped in. "Hey, Kate," she said, rather coolly, "don't go blaming him for saying something, from what I can gather it sounds like there's plenty you should have told me by now but haven't." Kate avoided Charlie's gaze and that gave the other twin all she needed to know. "Oh, so you have been keeping stuff from me then? And yet you're stood here having a go at Castle when something he said accidentally just so happens to be the thing you're hiding from me."

Charlie's tone strongly reminded Castle of Beckett's voice when she was particularly angry or frustrated. Usually at him, sometimes at a suspect, but he could tell it was working, Beckett was unusually quiet given that Charlie was potentially starting an argument.

"Castle," Charlie said and he drew his gaze away from Kate to look at her twin. "Thank you for accidentally saying what you did today, it seems to be fairly important. You're welcome to stay, but unless you want to see Kate and I when we get really mad at each other, maybe you shouldn't be here.."

Castle was actually contemplating staying, purely for the fact that Kate and Charlie getting angry at each other was sure to be highly entertaining to say the least, but then he remembered that Kate was still sort of angry at him, and if he were to stay, she would end up dragging him into an argument too, so he figured it was probably best to leave them to it. Kate Beckett angry at other people - cool. Kate Beckett angry at him - not cool.

"Yeah, I'm gonna go," he said, walking over to the door, "I'll uh, call you later," he added to Kate, who just shrugged and remained silent. He didn't envy Charlie right now, although she'd done nothing wrong, he was fairly sure that Kate wasn't in the mood for the conversation they were about to have and that was never going to end well. With half a smile at Charlie, he slipped out of the apartment leaving the girls to talk. Or scream and shout, he wasn't hanging around to find out.

Once Castle had left, the apartment was eerily silent for a few moments. It was Charlie who broke the tension, sinking onto the couch and saying, "so, what haven't you told me?"

Kate stayed rooted to the spot for a minute before joining her sister on the couch, she sighed as she sat down and contemplated where to start? Where she killed Coonan? Montgomery's involvement? That fact that she still wasn't safe? But then four years of working with Castle hit her - all good stories should start at the beginning, which in this case was Rick looking into the case when she had asked him not to.

"So Castle told you he looked into moms case?" Charlie nodded and Kate continued. "Well what he didn't tell you was that he found something that blew the whole thing wide open - it wasn't a random mugging, Char, mom was murdered as a hired hit."

"Wh..I, how? Why?" Charlie was lost for words. For the last thirteen years she had believed what the police had told them - that their mom was simply in the wrong place at the wrong time. She had accepted that and moved on, but now Kate was telling her it hadn't been random?

Kate sighed again, she was really starting to wish Castle was still here, he'd be able to help her explain it so much better than she could do alone. Where did she start? "Castle had some top rate forensic pathologist look over the case files and he noticed that the wounds were inflicted by someone who knew what they were doing. We didn't really have much more to go on at that point, but a couple of months later, we had a victim in homicide with matching stab wounds. Eventually, after being played by the victims brother, we figured it was the brother who had killed mom - Dick Coonan his name was," she paused letting out a shaky breath. Now that she had started she felt a little easier, but she still wasn't looking forward to explaining the rest.

"Wait, was?" Charlie questioned and Kate nodded.

"Yeah, he'd already signed the papers when we realised it was him. He pulled a gun on Castle and made us walk him out. My captain at the time, Montgomery, realised what was happening and stopped us and I managed to talk him down. I knew without a doubt that Coonan would kill Castle in a heartbeat and I couldn't let him do that."

"So you were just gonna let moms killer back out onto the streets?" Charlie asked and Kate didn't miss the anger in her voice.

"Charlie, I'd spent the best part of ten years desperate to find something in that case but I finally put it to rest a little while before Castle came along. Nothing we did would ever bring mom back but letting Coonan go was the only way of making sure Alexis didn't end up like us. Her mom isn't around, Castle is all she has, well apart from her grandmother, but I couldn't do that to her, make her go through what we went through," Kate explained, desperate for Charlie to see her reasoning.

"Okay I see your point," Charlie conceded, "so what happened next?"

"Castle managed to get away from Coonan, but he pulled his gun on Castle so I did what I was trained to do - I shot him."

"Good," was all Charlie responded. "What?" She asked at the look Kate gave her, "that man killed our mom and he deserved nothing less!"

"Mm, I guess you're right but it means that we still don't know who was behind it, given that I killed the one person who could have told us."

"Look, Kate, you did what you felt was right in the moment. And you were right - I know you couldn't have lived with yourself if you hadn't done everything you could to stop Alexis being left without her dad. So, is that all you know?" She asked.

"Uh no..so you know how I was shot at Montgomery's funeral?" Charlie nodded and Kate explained the rest of what they knew, with Montgomery's small involvement and how he'd died to protect her, but that she still wasn't completely safe and she knew she wouldn't be unless they ever found out who was behind it all.

"And I take it Castle knows all of this?" Charlie asked.

"Yeah, he's been there with me for it all, Char. I hated him for doing what he did but I know he was only trying to help and I guess he did. I couldn't have done it without him, I wouldn't have survived another minute looking into that case if I didn't have him by my side every step of the way."

"So," Charlie said, "why are you still sitting here? Go and get your man, Katie."

"No, not now," Kate said, "I'm still angry at him for what he's done today, I think it's best we have some time to cool off."

Something in what Kate said flipped a switch for Charlie. "What is your problem, Kate?" She half shouted, shocking Kate as she did. "The man has been there for you say in, day out and yet you're still blaming him for something you did? It's your fault I didn't know about what you'd found in moms case because you didn't bother to freaking tell me. Afraid I couldn't handle it? I guess I'm not the indestructible Kate Beckett after all, maybe I did need protecting," she spat out sarcastically. She was angry, seething actually, that Kate had failed to tell her all of this when she should have done but was still blaming Castle for letting something slip accidentally.

"Charlie," Beckett pleaded, "come on, it wasn't like that-"

"Wasn't it? Because from where I'm sitting we're having this conversation about two years too late, I should have been one of the first people to be told when you caught moms killer and the same when you found out more. But no, I wasn't here so I didn't matter. You know what, maybe there's a reason you and Castle aren't together, maybe you're just too selfish for anyone who could possibly give a damn about you," she shouted, jumping off of the couch and grabbing her jacket before disappearing out of the apartment before Kate could even realise what had just happened.

Three hours later and Kate was pacing the apartment. She had tried calling Charlie at least ten times but all calls had gone to voicemail - Charlie didn't want to talk to her. The only comfort Kate had was knowing that she hadn't taken her passport, meaning she couldn't just jump on a flight to escape.

Her cell rang and she grabbed it quickly and pressed the answer button. "Charlie?" She asked quickly.

"Uh no, it's me," came Castles voice. "Everything okay?"

Hearing his voice just resurrected her anger - perhaps Charlie was right and she shouldn't have blamed Castle for what he'd said, but if he hadn't then Charlie would still be here right now and Kate wouldn't be worrying about the many possible disasters that could have happened.

"No, everything is not okay! Thanks to you not keeping your mouth shut, Charlie got angry with me and stormed out. That was three hours ago and she isn't answering my calls and I have no idea where she is!"

Surprisingly, Castle seemed just as angry. "Don't you dare blame me for that, Kate. I know I shouldn't have said anything but all I said was that I looked into the case, I didn't tell her anything about what had happened - given that you should have done that years ago. But then again, you're good at avoiding conversations that don't play to your advantage, aren't you?" He said before disconnecting the call without warning.

Kate froze in shock. Not only was her sister out somewhere angry with her, now Castle was too. And the worst thing was that they were both right - she should have told Charlie everything when it happened and Castle was right about it not playing to her advantage - she'd almost lost Charlie with how she'd handled their moms murder and the reason she hadn't told her what she'd found was so that she didn't lose her for good.

Picking up her cell again, she scrolled through her contacts before pressing dial. It rang a few times before it was picked up, "Lanie," she half whispered into the phone, "I've screwed up.." And she cut off the call, tears streaming down her face.

A/N: *hides under pillows whilst waiting for responses* - I'm like 98% sure that a fair few of you aren't going to like this chapter because it wasn't fun and fluffy, but I would still appreciate some feedback - just please please don't be too mean! And please don't give up on it just yet, happier times are coming!

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