Castle wearily makes his way from the elevator to his front door. He normally would be glad to be getting home after a long day like this, but the thought of getting home to an empty apartment just depressed him.

When he enters he notices something off in the kitchen. He switches on the light and is surprised to see Kate sitting at one of the stools at the breakfast bar..

"Hi."

"Hi," he responds. When he left the precinct she had thanked him for his help, but hadn't said anything else about them or the moment they'd shared at the prison. "What are you doing here?"

"I'm sorry." She pushed her hair behind her ear. "Should I not have come in? It just felt too weird waiting out in the hallway. And I really wanted to talk to you tonight, before I lost the nerve."

"No, it's fine. This is still your home Kate." He takes a seat on the stool next to him and turns to face her. He should probably be pissed at her, but he's just grateful that she's finally ready to talk about this.

"I, um. I," she's avoiding eye contact. "I think there's something wrong with me."

"Okay," he says reaching out to cup her face with his hand. "That's okay, Kate. If there's something wrong we can figure it out. Together. But I need you to tell me what the problem is."

She doesn't answer right away, and Castle can see that she's been crying. "Kate, honey, you can tell me anything."

"I'm sorry." She finally looks him in the eye. "I'm so sorry, Rick. I felt so horrible earlier when you asked what you did wrong. You haven't. You haven't done anything wrong. You're such an amazing husband. I didn't want to leave you. I just….I feel like I'm not even in control of what I'm doing anymore."

"What do you mean?"

"I don't know, I just made this terrible decision, and it's so unfair to you. And I know how terrible it is, how stupid it is, but it's like something inside of me is forcing me to do things." Kate gets up and starts pacing the living room. "I feel like I'm watching myself do things and I don't even know why."

"Are you saying you're hearing voices or something? Because we can find a doctor." Castle walks across the room to stand in front of Kate. "I'll find the best -"

"No, no, no." Kate interrupts him and takes his hand. "It's not that bad, I'm not delusional. I know what's happening."

"Then I'm not sure I understand."

Kate steps back from him and takes a deep breath. She knows that the next part of this conversation will be harder for him to hear.

"It all started with Alison Hyde."

"From the AG's office? You mean this is connected to Locksat?" It made sense when he thought about it, that's when all this started. He knew she would feel burdened about the deaths of her old team, he just hadn't understood why she had to leave because of it.

"She's not Locksat." Suddenly, something in her voice tells him everything he needs to know. He can't believe he didn't see it before. He saw the start of it when he found her on the run with Vikram. That obsessive trait in her he thought had been long buried.

"Why do you think that?"

"It's too easy. Too clean. And before you say I'm obsessing about it, I'm not the only one that thinks so."

"What do you mean?"

Kate hesitates and looks away.

"Tell me." He says it firmly and moves so that he is still in her eye line.

"Look Castle, there's something I didn't tell you about when I was on the run."

"So much for no more secrets." He mutters. He's trying not to get angry, because he really wants to work things out, but he doesn't like what he's hearing.

"I'm sorry. I meant that when I said it. I was going to tell you about Rita once we were alone, but then….everything else happened." Kate moves and sits down on the couch, taking his arm and pulling him down with her. After they are settled she continues. "Vikram and I were ambushed where we were hiding for the night. This woman showed up to help us. She saved our lives."

"Who was she? Why not tell me right away?"

"She's CIA. She said she'd been tracking Locksat for years. It's highly classified." Kate paused and looked at him carefully before continuing. "She also said she was your stepmother."

"I...what?" That was truly the last thing he would have expected to come out of her mouth. "My father never said he was married."

"I know. She said that it has to stay secret because of the work they do." She looked at Castle's face to see how he was taking the news, but couldn't read his face yet. "She seemed trustworthy."

"And she told you to keep working this case? Because that doesn't sound like the advice a trustworthy person would give." Angry. He was definitely taking the news with anger.

"Actually, she told me to stop." After a pause she continued, "She said she was working on it, but I should go back to my life and be glad I was out of danger."

"So why didn't you? Kate this guy tried to kill you. He did kill several other people."

"Exactly. He killed Rachel and 4 other people I worked with. I can't just let that go."

"Why not? Why not let it go for your own safety? I thought we dealt with all this before."

"So did I. I wasn't going to take any unnecessary risks to bring down Bracken. But when I was at the AG's office, I couldn't help myself but do a search for him in the FBI database. And two years later 5 people are dead because of it."

"You couldn't have known that was what was going to happen," Castle said gently. He's still mad about all this, but he can tell she's beating herself up and he hates to see that.

"Those agents were all good people, Rick. Two of them had young children. Kids that are now going to grow up without a parent, and never really know why. Never see justice being served. Things like that matter, trust me."

"I know they matter. And I know that finding justice is important to you. It's one of the things I love about you. But you're not responsible for some psycho killing innocent people. And you don't owe anyone your life to get that justice for them. Pursuing this will very likely lead to that."

"I know. I know. That's what I keep hearing. But I can't let it go." Tears start to fall down her cheeks. " That's why I left. I knew if I told you I was working on this, you'd want to help. Then if you got hurt because of it, it would be on me. I'd never be able to live with myself for doing that to you. To Martha or Alexis."

"And how am I supposed to feel if you get hurt? Did you think about that?"

"At least you'll be alive."

"You don't get to make choices like that by yourself Kate. Do you know how awful I felt when you walked out on me? But that's okay because I'm alive"

"I know. I know it's terrible, but like I said I can't help it. I may be able to stop for awhile, but I feel like it's stuck inside me. What if I try and stop and one day make a mistake like searching the database. But this time, you get hurt? Get killed? I told myself I was leaving because I felt like I needed to go off and finish this so I don't have to worry about it haunting me."

Castle pause studying her closely.

"Kate did you really think if you'd told me all this, I would encourage you to keep investigating? That I'd help you?"

"Yes?" She looks at him hesitantly. "You said we should do things as a team."

"Right. And one of those things is stay alive as a team." He sighs. "Do you remember the fight we had right before we got together? I wanted you to stop chasing your mom's killer because life was more important. I thought you realized I was right when Maddox tried to throw you off a roof. That you decided I was more important than some case. Any case."

"I do remember that fight. And I did decide that." Kate closed her eyes for a minute. She still remembered that moment when she was hanging off the building. In a strange way, it was one of the best moments in her life. It's what gave her the final push to dive into a relationship with Castle.

"Then you know I'd never want you to unnecessarily risk your life over a case, no matter what the details are." He shook his head, anger showing through again. "I think you didn't tell me because you knew I'd tell you to stop and you didn't want to. It's like an alcoholic hiding their drinking because they know their loved ones would try and stop them."

"Castle, I am not an alcoholic." Kate snapped. She jumps up from the couch with her hands out, a silent warning telling him to stop. But he doesn't back down.

"You don't have a problem with alcohol, but it sounds like an addiction to me. How would you feel if your dad came to you talking about how he just couldn't help but drink. And his option for dealing with it was to go out and drink as much as possible until he got it out of his system." He was being harsh and he knew it. But he wanted to get through to her.

"I…it's not the same thing at all." Except part of her knows it is, and she steps back even more, her defense mechanisms kicking in..

"I think it is." Castle tells her, getting to his feet, not letting her put space between them. "And I know that's hard for you to hear because you don't want to think that you hurt me as much as your dad hurt you when he was drinking."

Hearing that's like a punch in the stomach, because Kate remembers exactly how it felt every time she begged her dad to stop drinking himself to death, only to have him ignore her. He eventually sobered up for her, but their relationship was never the same.

"I'm sorry." she says. "I...god, I don't even….I hope that isn't true, that you don't feel like that. That I haven't hurt you that much. But my dad drank for years. This is different."

"Well, don't make his mistake. Stop now before this goes too far. Before we're too damaged to recover."

"I'm not sure it's up to me though. Like I said, I feel like I'm not in control of this. It's -"

"Kate you just have to decide to fight it. If you're tempted to investigate like you were when you did that FBI search think of this moment. Think of me. That should be enough to control yourself."

She puts her head in her hands, taking deep breaths. She feels like she's having a panic attack, something that hadn't happened to her in years. After a few minutes she feels Castle's hands gently touch her shoulders.

"Kate. If you really believed that what you're doing is okay you wouldn't have come here tonight." He can hear her crying and can't take it anymore. He pulls her around and pulls her into a hug. She wraps her arms around him tightly, sobbing into his chest.

"I'm sorry," she says finally pulling back. She looks him in the eye and strokes his face gently. "I really am sorry. About everything. I just don't know how to fix this. I don't know how to change this thing inside me. But of course you're enough. I love you and you are the most important thing in my life. I don't want to hurt you anymore and I want to save our marriage."

"Well, good." He smiles tentatively at her. "So do I. I'm still upset, but I want to work it out. But you have to stop this investigation. No question about it, okay? And I think you need to talk to someone about this obsessive tendency you have."

"Castle I can't tell anyone about this case without putting more people in danger." Her hand drops from his face.

"You don't have to tell them the details," he tells her. "But you have to work on this. Otherwise we'll just end up having the same problem when some new case becomes personal down the line."

"I've tried therapy before."

"I thought it helped you before."

"Well, so did I," Kate tells him with a wry smile. "But here we are."

"Then maybe you just need a refresher."

"I don't think it's that simple."

"Kate, I'm serious about this," he says firmly. "If we're going to make this work, you need to do this. I can go with you if you want. But you can't tell me you're not in control of your actions and then expect me to think you can change without help."

"Okay," she says nodding reassuringly. "Okay, I'll do it." It was an easy call, she'd do anything he asked to make up for what she did to him. Losing him was worse than the discomfort of going back into therapy.

"And you'll stop whatever investigating you've already been doing?"

"Yes."

"And move home? Tonight?"

"If you'll have me," she said smiling

He smiles, then grabs her waist and pulls her toward him, giving her a deep kiss. He knows they have an uphill battle, but he is so glad to know what's going on with her, to know that they still have a shot at their happily ever after.

"I love you," she says when they finally pull apart.

"I love you too."