Castle's own hand knocking on her door breaks him out of his trance. As he looks around, he's quickly realizing where he is, and, with a snort, supposes this was his next logical step.

Footsteps jolt him further out of his head and into reality, and he paints a facade of calm onto his face, knowing that he can't head into this with his anger apparent, or it will all blow up before it begins.

The doorknob turns, and Kate's face is a mixture of puzzlement and amusement at seeing her shadow unexpectedly at her door.

"Hey Castle," she opens the door to let him fully into her apartment.

As she turns to close the door, she hears him utter a single "Hey" and spins in time to watch him wordlessly sink into a chair and cover his face with his hands.

"Castle?"

He can't decide whether to sit or stand, so much conflicted emotion coursing through his body. With a frustrated sigh, he heaves himself up again as she folds herself onto her sofa, the dissonance of the actions not lost on him.

With a brief close of his eyes to brace himself, he looks her straight in the eyes and decides to just plunge headfirst.

"Tell me. Just tell me why." He watches the confusion on her face appear. "Tell me. Tell me why I have to hear from Alexis that you remember. Tell me, Kate." He is inching closer to her, and he can feel his body begin to break, feels his hands begin to shake, and he doesn't want to lose that. He wants to keep his cool for this, he knows that this isn't a conversation for screaming, this isn't meant to be an argument. He sees the blood drain from her face, and almost moves forward to catch her as her knees buckle. But touching her will do him in, will make the anger manifest into something physical.

"Castle -"

It sounds tight and distressed when it passes her lips, and it pokes at his gut, but he can't seem to find that calm argument that was in his head on his walk over.

"No. No excuses. I want you to think, clearly, before you answer this." He knows he sounds like he's scolding a child, but he can't get enough control of himself verbally. He knows what Alexis was going through, that all the words are there, and once they start, they just come tumbling out. "I want to know why you would talk to Lanie about me, about us, about what happened, and why for months, for months you would ignore it."

"I don't … I don't know, Castle."

He whirls on her then, the anger clear in his eyes. "You don't know?" He bites off a laugh. "Alexis, Kate. I had to hear it from Alexis. My daughter. You know, I thought if I would ever hear it, it would be from you, but Alexis? Oh no, that's rich, Kate. Let me tell you, the guilt in her eyes, knowing that what she had to tell me could possibly break me? Broke my heart more than I thought it could. To know that my suspicions actually had some merit to them." He wants to cringe at the look in her eyes, for putting it there, but he just can't stop. It's hurt for so long. "Oh detective, you couldn't possibly think I had no idea? The PTSD, the breakdowns during the sniper case? It's hard to have a reaction to something you don't recall, isn't it?"

"No." She whispers, her voice bringing him back down to reality, to the realization that he's pacing her living room, her anxiety clearly written on her face. "Castle, I wish there was something I could say to you, something that could help this, but I know it doesn't exist."

He sighs and sits on the chair opposite her sofa, where she's curled her legs under herself, showing him the clear stress that he's putting her through.

She looks up at him, guilt and fear written on her face, and what he hopes aren't tears glancing off her cheeks. "Castle, I just … I couldn't do anything. I've been so close to apologizing, and whenever 'I'm sorry' comes close to coming out, I realize it's not going to be enough. Do you know how many times I wanted to tell you everything, and then realized I wasn't whole enough to do it? That I wasn't enough of a person to jump into what I know would be serious?"

He huffs at this, his anger bubbling to the surface again. "Kate, please. That's an excuse, and you know it. Lanie said -"

The look in her eyes tells him everything. It flashes, changes, her own anger brimming in an instant. "Lanie said? Really, Rick. You want to talk about hearing it second hand? Third hand? How about you hearing it from Alexis, and instead of asking me about it, you head straight to Lanie? Did you not trust me enough to come to me, instead you had to head to my best friend?"

He's standing again, his figure towering over her on her couch. "It's not a matter of trust, Kate! What was I supposed to do? You didn't trust me enough to tell me the truth yourself, so I guess, yeah, maybe it is a matter of trust." He huffs, and sits back down on her chair. "Kate, I just … dammit, Kate, I didn't want to fight with you on this. I just want … I just want to know why. Why you couldn't trust me, just … why." He feels like he's just run a marathon when he drops back into the chair. His brow is moist and his shirt collar feels like it's choking him.

The tears glancing down her cheeks can't be mistaken now, and he hates that. He hates that she's been able to take his anger and diminish it. He wants to be angry, he wants to yell more, but the look on her face? The pain, the anguish, the guilt? It eats at him more than he can bear, and the tears are the final knife through his heart. He hears her sniffle, and he looks up at her folded body.

"Castle, after I came back to your book signing, I told you that I have that wall, that I have to figure out my mother's case before I could be in the kind of relationship that I wanted to be in. Before I could be in any relationship. You've … you've made that wall seem less confining, and it terrifies me."

There's too much pressure sitting down, it feels like the whole atmosphere is collapsing on her. She heaves, pushing off the couch to stand and see the city outside of her window.

"But I can't let it go, Castle. I know I said I'd stop, but I can't. Maybe for now, but not forever. My case, my mom's case, it's too big of a piece in that wall. I have to know. I deserve to know."

When she turns away from the glass his jaw is clenched. He's paled, and when she says his name he doesn't meet her eyes.

"Castle look at me."

He doesn't.

"Look at me, dammit!" She's seething, she knows he's keeping something from her. Her legs feel like stone and she can't move, her stomach rolls with fear.

He turns to her with eyes full of regret. His fist is covering his mouth as he stares right at her, not saying anything.

"You know something." She points an accusatory finger in his direction. "You know something, and you're not telling me. What is it Castle? Because we're already pissed at each other."

"I told you to back off your case."

She can only nod, waiting on baited breath for more.

"But…" he sighs, "what I didn't tell you, was that…I didn't. But a man called me and said-"

"Who?"

"I don't know! A friend of Montgomery's. I don't know his name."

"What the hell, Castle! You don't know this person, but you let them know about my life? My personal life? Talk about trust? How can you trust someone you don't even know?"

"He said he knew Montgomery. And he knew how to keep it quiet. But he can only keep you safe if you stop pushing."

She sucks in a breath, nearly choking on the air. How could he do this to her? Again. Go behind her back. Again.

"You tell me not to go running into fire, but it's okay for you? What do you think? You're the big strong man, so you're allowed lie if you say it's to protect me?"

"Yes!" He challenges, jumping up from her couch. "That's exactly what I think! And you know damn well why! Or did you forget that you haven't forgotten how I watched you die in my arms?"

They're standing toe to toe, each with rage burning at their eyes, their bodies heavy with adrenaline and anger.

The longest moments of either of their lives pass before he dares speak again.

"Look, it's just….a lot." He takes a deep breath, running a hand through his hair, "I think we both need some time to think. About us. And…everything. I'm going to go." He pivots, heads to her door, but stops and turns back to her as his hand grips the knob. "I'll call you in a few days. When we can both act like adults."

The tears are finally spilling from her eyes when Kate hears the door slam and everything crashes in. She can't think straight, and she's mad as hell. She flies through her apartment after locking and chaining the door behind him – the ass – stripping her clothes as she goes. She steps into a scalding hot shower, not caring that her skin will be red and raw when she gets out.

Maybe this pain will make everything else hurt less.