AU:Set season five,on the way to Ryan's wedding he asked Beckett to marry him.
She puts the finishing touches on her makeup and smooths down her knee length, mint green cocktail dress. She walked out into the living room, where Castle was waiting for her. "What do you think?"
"I think," He said walking towards her, grabbing her hand. "You look beautiful." He kisses her cheek and smiles.
Kate can feel a blush creeping up her neck, "Is there ever a time when you don't think that?"
"No, because no matter what the occasion, you look beautiful." He smiles at her and she tries to stop her cheeks form blushing but it's too late.
He starts to the door, talking in a sing-songy voice. "At least with Ryan's wedding we'll get some ideas." He turned to look at her, a smirk on his face.
"What, Castle?" Her eyes are wide and her breath hitches.
He walks back to her. "Oh, I better ask the question first."
She freezes. 'Oh my God, he's proposing!' is the only thought in her head as he pulls out the ring.
"Kate, five years ago, I fell in love with you, and I'm still so in love with you."
She tries to stop the tear in her eyes, but can't. This is perfect.
"Before we met, I didn't know what love was. I didn't know what magic was until I met you. You hold a special place in my heart that I thought would never be filled. You fit so perfectly into my family. Mother has already taken you as a daughter, and Alexis has taken to you as a mother. And I want to take you as my wife and partner in life. So, Katherine Beckett, will you marry me?" He looks up and sees the tears in her eyes. He hopes he hasn't jumped the gun and her old self takes over and runs.
She laughs and cries holding out her hand. "Yes."
"Really?" He doesn't know why he's surprised, but he's so, so happy.
"Yes, absolutely, Castle, I will be your wife."
He slips the ring onto her finger and kisses her hand. He stands up and takes her hands in his.
She looks him in the eyes, knowing what he was thinking. "You were thinking I was going to run."
"All of me was hoping you wouldn't." He's honest with her.
"No, Castle, I'm done running. This is the life that I want. Th only life that I want is with you." she leans in and so does he, pulling her to him. They kiss right there in the loft and rest their foreheads together; bliss.
While waiting for the wedding to start, Kate slips the ring off of her finger. As much as she wants to wear it, it's Ryan and Jenny's day, not her and Castle's. But it will come soon enough. He laces his hand with hers and she rests her head on his shoulders.
When the wedding is over and the priest says "You may kiss the bride.", Beckett swings her arms around Castle's neck and kisses his cheek.