*Time Will Tell au, based on the premise that the time-traveling case happened in Season 4. Set after The Limey. I changed a teeny part of their "future" because I felt it fit better with Beckett in Season 4. Also, the title is taken from the book of Ecclesiastes.

(Kate)

"Real charmer, that one. I can't believe you marry her."

Doyle's talking to Castle, and she's on the phone with Dispatch, but she hears his disbelieving comment. Oh, does she hear it.

There's a tense pause before Castle asks, "How do you know I marry her?" And that hurts even more, because right now he sounds more skeptical than she has this entire case.

Doyle rambles on, seemingly unaware of the tension filling the room. "One of your book jackets," he explains. "Richard Castle lives in New York with his wife, Lieutenant Kate Beckett, and their three children."

She's lucky that her phone call ends just a few moments after this proclamation because she's totally thrown by this so-called revelation of her future. A few weeks ago she would have jumped at the chance to have that future with Castle, but now she's just hoping for any kind of future at all.

They don't get the chance to talk about it until later that evening, when they've exhausted all of their resources and energy for the day. It's late, they've had a long day, and Kate's entire body aches from being tackled to a concrete floor. She hasn't forgotten how Castle had pulled Ward off of her, taking the brunt of the beating on himself. It gives her just enough hope to broach the subject.

She sighs, stretches her arms above her head. "I'm thinking we should call it a night," she tells him. "We're not gonna get anything else done tonight."

Castle nods and stands to pull on his jacket. "Sounds good to me," he says. He sighs, glances towards Holding where Doyle will be (hopefully) spending the night. "You know, this being my last case and all, I was really hoping that the time-traveling killer theory would pan out."

Her heart plummets into her stomach, and she just barely manages to keep her face from falling. "You don't believe Doyle's from the future?" she asks, trying to keep her voice light and teasing.

"Sadly, no," he replies. "He showed his hand when he tried to tell us details about our futures." He shakes his head. "Nah, he's either crazy or a very good liar."

She shrugs. "Even so, not all of his predictions were that far-fetched."

Castle nods. "That's true," he admits. "I can definitely see you as a lieutenant someday. But all that other stuff? No way." He chuckles. "Can you imagine the two of us married?"

Kate bites her lip, hesitates because yes, she can. She can picture all of it clear as day, and it's killing her that he doesn't seem to. "Are you saying you can't?" she asks, trying to mask the tremor in her voice.

"Well, I guess I can," he concedes. "I do have a pretty vivid imagination. I just can't imagine it working out well."

A quiet "oh" is all she can manage, but if he notices, he doesn't say anything. She busies herself with putting on her jacket and packing up her things while she blinks back tears.

"All I mean is that if two people go into a marriage, and one's feelings are decidedly stronger than the other's, it's not going to work," he says. "Trust me, I know from experience."

She nods, and tears start to fall of their own volition. Because now she knows why he's been so distant, so weird lately, and it hurts more than any physical pain she's endured over the past year. "See you tomorrow?" she asks hopefully, still avoiding his eyes.

"Of course," he responds cheerfully. "Last case, Beckett. I wouldn't miss it for anything."

Last case. He's been saying that all week, but she's just now starting to believe it. The realization that he doesn't love her anymore is slowly destroying her. She manages to make it home before breaking down, but once there she curls into a ball in the middle of her bed and cries herself to sleep.

The next day, they find Ward and stop him from killing his third victim, but all Kate can think is that it's too soon. It's all happening too fast. Soon enough, Castle will walk out of the precinct for the last time, and there's nothing she can do to stop it.

It's getting late again, and surprisingly he's still there, even though Ryan and Esposito have been gone for at least an hour, and all he's doing is watching her do paperwork. She almost wishes he'd just leave already and get it over with. Almost.

Finally, she sets her pen down and closes the file. She sighs, looks over at him, tries to smile. "All done," she announces, tries to swallow past the lump in her throat. "I guess...I guess this is it."

"I guess so." He holds out his hand, and she takes it, holds on a few seconds longer than she normally would. She drops it reluctantly, averting her eyes at the same time.

"We'll miss you," she says, her voice catching.

"It's not like I'm leaving the country or anything," he says. "I'll visit."

Kate looks up at him, not bothering to hide the tears in her eyes. "It won't be the same," she whispers. A tear falls, and he reaches out to wipe it away, but she backs away before he can touch her.

"Kate..."

She has to stifle a sob because it's the first time he's called her Kate in weeks. She turns her back to him, bracing herself on her desk. "Just go," she tells him, her voice breaking. "Please."

For a moment she thinks he's going to listen, but then his hands are on her shoulders and he's turning her to face him. "Kate," he murmurs, tilting her chin up so she's looking him in the eyes. "What's wrong?"

She tries to look away, but he won't let her, so she closes her eyes, takes a breath and asks, "What did I do?"

She's met with silence, so she continues. "I mean, I know I must have done something to make you...to make you stop loving me," she says. She opens her eyes, looks at him pleadingly. "Just tell me what it was, and maybe...maybe I can fix it."

Castle looks down momentarily, and when he looks back at her, his eyes are blazing with anger. "Do you honestly think I could ever stop loving you?" he demands. She nods meekly and he growls in frustration. "God Kate, the only reason I'm leaving is because I love you so much, and I can't stop, and that's never going to change if I have to be around you, day after day. It's killing me, Kate." He sighs, hangs his head. "Why do you even care?"

She finally reaches out to him, touches his cheek, brings his gaze back up to her eyes. "Because I love you, too," she whispers. "And the thought of losing you..."

He cuts her off with a kiss so passionate and breathtaking, she finds herself clinging to him for support. When they break apart for air, neither goes far, their foreheads and noses touching.

"We need to talk," she murmurs, nudging his nose with hers.

"That we do," he agrees. "But would it be alright if I kissed you some more, first?"

Kate grins, a happy tear slipping down her cheek. "I think that can be arranged."