If Only
By: S.K. Knight

Disclaimer: I don't own Castle, if I did, this episode would've gone my way. Oh, and I don't own the "if only" line or the "mystery I'd never solve" line.

A/N: This is a two-shot set partly in 3x22 (To Love and Die in LA). Hope you enjoy! PS For the record, THIS is what SHOULD'VE happened, Marlowe. Oh, and please REVIEW! This story is dedicated to my friend, Pelin. (MsStanatic on Twitter) THANK YOU, PELII!

Kate breathed in deep as she leaned against the door in one of the rooms in the swanky LA hotel suite her, well, partner had purchased for them. He had told her that night that she was the mystery he was never gonna solve. But maybe, she thought, it's the other way around. Maybe I'm the one who's supposed to figure him out. Kate put a hand to her face and focused on her thoughts, trying to sort out her cornucopia of feelings, feelings she'd never bothered to acknowledge before but now, they were rushing at her all at once like a waterfall she couldn't stop. Those longing looks they had shared on the couch meant something, so she asked herself one question as she put her hand on the door handle: Am I in love with him? As she pressed down, she knew what the answer was. Kate looked around as she opened the door, but Castle had already gone into his room. There was nothing Kate could do but go back into her room, change, and climb into bed.

Rick cursed himself for letting her go back into that room without telling her. Telling her what? That you love her? C'mon, Castle, get a grip, you can't just tell her that you loved her since the moment you saw her. That's…that's crazy! Somewhere, in the back of his mind, he knew it wasn't. How easy would it be to just turn the door handle, walk in, and confess his love, right there in her room? Castle lay down on the bed in his clothes and allowed himself to dream:

Castle walked out of his room and quietly into hers. She was asleep but woke suddenly when she heard the door click and she reached for her gun in the nightstand drawer.
"Whoa, hey, Kate. It's just me." Castle assured her.
"I told you I sleep with a gun." Kate informed him as she put it down.
"I can see that."
"What do you want, Castle? It's two AM."
He falters a minute and then says, in a whisper, "I love you, Kate. I always have."
Kate is a loss for words but when she regains her voice, she says, "I know, and I love you too, Rick."
He turns to leave until she whispers, "Stay with me."
He turns and obliges, moving over to her bed. Soon, her mouth is over his and he feels her tongue gently running along his bottom lip and he moans and then she pulls him down onto her bed…

Castle's eyes flew open with a start and he sits up, looking around. It was still dark out. The digital clock on the night stand reads three thirty AM. I really am in love. He thought and it took only seconds for him to realize what he needed to do. He reaches his door and opens it without thought, going straight to her room. He hesitates as he puts his and on the handle. Just do it, for her, for Kate. He urged himself. With that, he opened the door quietly and slipped in, but Beckett didn't wake. He pondered whether to wake her, and decided this was too important to wait. He made his way to her bed; touched a gentle hand to her shoulder and her eyes flew open and she reached for her gun.
"Ssssh, Kate, it's just me."
"Castle? It's three-thirty in the morning."
" This couldn't wait." He told her, sitting on the bed.
"What couldn't wait?" she queried, sitting up.
Like his dream, he faltered. "I…I love you, Kate. I always have and always will."
Unlike his dream, Kate wasn't shocked.
Instead, she said, in a whisper, "I know and I do too."
It was Castle's turn to be shocked. "You know, how?"
She chuckled. "C'mon, Castle, you've done enough "research" to last you your entire life, I figured there was another reason and now I know I was right."
Castle smiled, and reached out a hand to caress her cheek. "It was you, it was always you, Kate."
She laughs and leans forward to whisper in his ear, "I knew it."
He pulls her in for a long kiss and gets up, making his way to the door.
She smirks at him as he looks back. "You know this isn't how things are supposed to go, right?"
He smiles back. "Enlighten me, then, Detective Beckett, how are things supposed to go?"
"You're supposed to stay with me." She whispers, getting up and walking toward him. She kisses him and takes one of his hands, leading him to the bed where they kiss and he hovers on top of her, running a hand through her long hair, kissing
until they fall asleep in each other's arms.

Two years had passed since Kate and Castle admitted their feelings that night in LA. When they had come back to New York, everyone knew something was up. Kate was smiling more, particularly at Castle, and Castle seemed happier than ever before. One day, while Kate was doing paperwork, Castle sat down next to her and smiled.
"What?" she asked, returning his smile.
"What will it take to get you away from that paperwork and to come on a walk with me in Central Park, hmm?" he questions.
"I have work to do, Rick." she protests.
He smiles. "Work can wait."
She sighs and gets up, taking his outstretched arm. "Ok, fine."
"Good." he says, as they make their way to her car. Lanie,
Esposito, Ryan, Martha and Alexis follow after they leave. Once there, Castle and Beckett meander slowly, hand in hand along a path until they get to a corner surrounded by trees with a fountain and a bench in the middle. Castle stops and Lanie, Esposito, Ryan, Martha and Alexis watched from behind a tree.
"What are we-"Beckett started, but he put a finger to her lips, cutting her off.
He got down on one knee, and pulled out a box with a beautiful diamond ring inside it.
Rick smiled softly and said, "Katherine Beckett, will you marry me?"
Kate smiled as she thought about the letter she read on the plane from LA, the letter Royce sent her and what it said. One phrase stood out in her mind: You never want to look back on your life and wonder if only. Kate took a breath, readying her answer.