Prompt from PatienceFortitude here on fanfiction: Castle or Kate are about to get married to someone else and the other...

Also, this is AU where all of season 4 happened, but Kate was still dating Josh, who was way more into their relationship than she was.

She runs her hands over the front of her simple white gown, smoothing the material even though she's done it at least ten times in the last five minutes.

She can't help it. She's nervous. Who wouldn't be? She's about to marry the man of her dreams.

Or not.

No, she's not marrying the man of her dreams. The man of her dreams will be sitting in the crowd, watching her marry someone else.

And there's nothing she can do about it.

Because she's stupid. She lied to him. She lied to Josh. She lied to everyone, all because she was broken. She still is. She still can't have the relationship that she wants. The walls are still standing strong and tall, like a fortress around her heart. And now, there's nothing she can do about it.

One person has been able to make a dent in those walls, and it's not the one she's marrying.

She run her hands over the front of her dress again, knowing that someone will be here to get her for her wedding any minute.

And, oh God, today is her wedding day.

So much for being a one and done type of girl. There's no way in hell that this marriage will work out—not with his schedule, her schedule, her walls, his lack of trying...and her love for someone else.

Why in the world did she lie to Castle for over a year? Why didn't she just dump Josh instead of getting back with him three months after her shooting? Why is she still stuck in this stupid relationship with a man that, if she's completely honest with herself, she doesn't love? And why in the world did she invite the man she does love to the wedding?

Oh, right. All that's because she's a stupid, broken girl who doesn't have the confidence to go and tell the man she loves that she loves him, or to say no to her boyfriend of two years' proposal.

And now, she's pretty sure she's hurting everyone because of one stupid mistake.

Esposito already came in to see her, to make sure she didn't think this was a mistake. Of course, she had denied wanting to back out and run for the hills...with Castle, no less. But she's pretty sure Espo didn't believe her. And then there was Ryan and Lanie, who were a little more sentimental about it and had her on the verge of tears when they told her that Castle still loved her—because apparently everyone knows, now. Even her dad told her this was a mistake.

But, you know, being the scared little wimp she apparently is when it comes to love, she can't bring herself to just cancel the wedding and hurt even more people.

She hears the door click as it opens and turns to meet Lanie's eyes filled with sympathy. She knows that's most definitely not how someone is supposed to be looking at you on your wedding day. She smiles back what she knows is a sad smile, and carefully takes the bouquet from her friend, walking out of the room and into the small space behind the church's main room.

"Writer Boy didn't bring a date, if that makes you feel any better," whispers Lanie.

She nods in response, but her head is screaming no. That's not better. Maybe, if he was with a date, she would be able to use her jealousy to get through the stupid wedding vows that she knows will be anything but kept. But now he's alone, and she's scared she'll back out of it all together as soon as she sees him.

It happens fast, too fast. One minute, she's standing there in her wedding dress, waiting for the stupid, annoyingly traditional wedding march song to start—Josh insisted. And the next she's standing at the altar, fighting to keep her eyes on his so she doesn't look like the scared girl she is.

There's a bunch of people in the church, but she can only feel one pair of piercing blue eyes on her, and she's fighting what feels like useless battle to keep herself from looking at him.

And then the preacher is asking if anyone has any objections to the wedding, and everyone turns to Castle, even her and Josh. She can only guess that Josh is trying to make sure Castle doesn't say anything. She's not sure what she wants.

But now he's standing and telling the preacher that he does object to the wedding, and suddenly she's struck with anger.

How the hell could he do this to her? Wait until she's getting married to Josh, who she really doesn't care about at the moment, but still? He loves her, she knows that, and she loves him, he doesn't know that, but he's waited until now to tell her again?

"Why?" she manages to get out, her hands releasing Josh's as she takes one step down from the altar. His eyes are shining, and she's being pulled towards him as if there's some magnetic pull between the two of them.

"Because I love you," he answers as if it's the most simple statement in the world. Her breath catches in her throat and she freezes on her walk down the aisle. She already knew, but hearing it again takes the breath right out of her. "But you already knew that, didn't you? You've known for over a year."

She nods, can't help it. There's no point in lying now. There's also no point in looking back at Josh, since there's no way in hell she's going through with this stupid excuse of a wedding now.

"Yeah..." she whispers, hating that they're having this conversation among all her friends and family, not to mention Josh's friends and family. "I'm so sorry, Castle. So sorry." Somehow, she's managed to get herself so close to him that there's only inches between them.

"Why did you lie, Kate?" he asks, straight to the point.

She takes a deep breath, shocked by his bluntness, but decides to be honest with him.

"Because I was scared, Rick. I was so scared of actually being in love with someone," she admits, feeling like her mouth is talking without letting her actually think first.

Everyone gasps around them, but the sound is drowned out as her eyes lock on his.

"I love you, Kate," he replies, eyes soft and filled with love. "And if that means anything to you, please, just don't marry him."

She answered him with a kiss—and she can't help but feel like they're in a storyline from Temptation Lane right about now—the feeling of his lips against hers better than anything she's ever felt before. And this is totally in appropriate at her wedding to another man—but she's pretty sure he's not even in the room anymore—but she can't help but moan as her lips open to welcome his tongue into her mouth.

"Get a room!" screams Lanie suddenly, breaking their moment of bliss. She pulls away, a blush instantly creeping up to her cheeks. But when his eyes lock on hers, they're dark and filled with want and she's biting her lips because of room doesn't sound half bad right about now.

"We have to talk," she whispers instead.

"Later," he replies, a mischievous sparkle in his eyes as he looks down at her.

She grins, teeth still holding her lips in place, and nods, deciding that talking can wait, that the room will be necessary soon, if she doesn't want to arrest them both for public indecency.

And the next time she's standing in the back room of a church, smoothing down the white lace of her dress, she's smiling wide and happy, about to marry the man of her dreams, for real, this time.