It takes her a while for her to notice it.

He's so bright, so alive, a permanent ray of sunshine in the mediocre clouds of her life that the sunny exterior distracts her from what's underneath. Maybe she lets it distract her a little, because it's so much easier than seeing things she doesn't want to.

It's just little things, little tiny things that shouldn't matter, but she's Beckett and he's Castle and they've been through hell and back together, so they do matter.

It's the way that, although he always, always remembers to bring her coffee, he can forget to feed himself until she reminds him in a bizarre display of role reversal.

And how sometimes when he smiles, it doesn't quite reach his eyes, although it often manages to reach her heart.

She worries about it, and over the next few months does exactly what she knows he'd do for her. Drops coffees and pastries off on his desk, invites him back to her place for dinner and wine, and sometimes grasps his hand as if she can anchor him to the earth. To them. To her.

(He doesn't say anything about it, but he squeezes her fingers or rasps his thumb over the back of her hand, and that's enough.)

But then Alexis calls her, asks to meet up, and there in a smoky cafe in central New York, the bravest teenager Kate Beckett has ever met dissolves into tears.

"It's Dad. Kate, I'm worried... I don't know what to- I don't know. I don't know anymore."

She does the only thing she can and pulls Alexis into her, her hands spanning her spine and holding her together.

"I know, Lex. I know."

She takes the thoughts home with her when she leaves, and lying in bed at one in the morning with her pillow clutched to her chest, she realized that somewhere in between watching her die and thinking she didn't remember, Castle fell apart. And she didn't notice, because she fell apart too. But now she's whole again, and he's still shattered.

It lingers in the back of her mind, that thought - I didn't do enough - but it takes a few weeks to tick by until she finally reaches the point where she can't take it any more.

It's a crisp Autumn night, and Castle's standing, hands in pockets and back hunched over, in the parking lot. Somehow he looks very small for the enormously tall man he is, and she misses the constant buzz of doing that he used to carry around with him. He's not playing on her phone, or jotting down notes. Just standing staring into space at ghosts she can't see.

"Hey."

It sounds too loud in the clear air and makes her wince a little, but at least it's out there in the open. He turns and she sees something of herself reflected in his eyes, from back when she was a lot less okay than she is now.

"Hey yourself." he replies, his voice cracking a little halfway through.

"Are you-?" Kate asks, trailing off half because she doesn't know what to say, and half because she doesn't know how to say it.

"Yes." She knows that he knows what she's thinking.

And then, because she can't find words - how can she, when the one man who always has something to say is standing silent next to her, she curls her hand around the curve of his forearm, her other hand's long fingers ghosting his waist, and feels him stiffen in surprise, then relax.

Maybe this was what he needed all along. And what he needs to break out of this, she's willing to give, because he's given so much to her.

Kate lets her wayward hand drift upwards to smooth his collar down, stroke his neck, needing to feel that there's still a bit of Rick underneath this man she doesn't know anymore.

"I'll be okay."

Her head jerks upwards at his words, finds his eyes locked onto her face, a stormy blue promise. Her mouth opens then closes.

"Eventually. And I know what you've been thinking, and it's not your fault."

"I don't- I should have done something." she says finally, her thumb scraping along the lobe of his ear.

"Kate, you know as well as I do that sometimes you have to let someone save themselves."

They lapse into silence again, because there's nothing, nothing she can say to that, no pretty words that can make him feel better, and god she hates this, hates seeing him so dark and silent and she doesn't have any words that can-

"I love you, Castle."

She says it because she doesn't have anything else, and maybe what he needs more than anything else is no more lies. Just the truth. So there it is. Castle draws in a breath but doesn't say it back. She doesn't expect him to; she already knows.

"I-" and then she runs out of words again and does the only thing she can think of; pushes herself up on her toes and slides her hand against the rough stubble of his cheek and kisses him. He's rigid against her for the briefest of heartbeats before she feels him soften, melt, start to give back.

It's the promise she couldn't say out loud, the promise of now and always and possibly a little bit of forever.

As his mouth slants against hers over and over, she recognizes that he tastes like Castle. Like Rick.

His hands come up to press into the small of her back, warmth burning through her jacket and branding her skin. She's comforting him and loving him and giving to him all at once, trying to clumsily make up for all the things she hasn't said.

When they finally break apart, she leans her head into the curve of his shoulder, presses her lips into his neck.

"Thank you." Kate mumbles against his skin.

"For what?"

"Letting me do that. Letting me do this."

He's silent, but his arms tighten around her, pressing her torso more firmly against him.

"Come home with me," she says softly, tipping her head back to gauge his reaction. "Dinner, and wine."

The smallest of smiles twists his mouth. "We could debrief each other." he whispers.

They uncurl from each other at almost the same time, but as the distance between them increases, her hand finds his and she leads him.

Anchors him.

Always.