Prompt: Post-season 5 AU. Castle and Beckett break up when she takes the job in DC. Nearly a year later, Beckett has moved back to New York and into her old apartment. On the night before Castle's wedding to a woman he started seeing for six months, he shows up at Beckett's place, to remind her that even though he's getting married, he'll always love her and care about her.
Taking that job in DC wound up being the worst mistake Kate Beckett ever made. She lost the love of her life because of it, but Kate also found she didn't have the stomach for the gray areas working at the federal level entailed. She tired of looking the other way while powerful people walked free; it reminded her of how a certain Senator was still walking free, advancing up the political ladder when she knew he had her mother's blood on his hands.
She lasted a little less than two months before returning to New York, eventually finding her way back with the NYPD. It was awkward, working cases with Ryan and Esposito again, but maybe the awkwardness was because of who wasn't there.
Ryan had told her last month to call him, to try mending what had been broken. She almost did, despite her foolish pride, but an article in Page Six that fateful morning changed her mind.
Richard Castle was getting married. Not quite a year after their break-up, he was set to walk down the aisle for the third time. With someone not named Kate Beckett.
Kate didn't know how to deal with that. After a night out with Lanie three weeks ago, a night that included some dancing and more than her fair amount of booze, Kate had considered giving Josh a call. Lanie, ever the sane one when it came to matters of Kate Beckett's heart, had stopped her.
Now here it was, the night before Castle's wedding, and Kate was alone in her apartment. Four Nikki Heat books sat on her coffee table; Frozen Heat wound up being the last one. She remembered that he had been working on another one before they broke up, but apparently their split made finishing the book too painful.
Her heart broke at the realization.
Kate picked up her copy of Heat Wave, her fingers trailing over the silhouette on the front. Her eyes flickered to the name atop the cover, her heart skipping a beat the way it always did when she saw his name. She couldn't get away from him; no matter where she went or what she did, Castle was always there.
Just another reminder of how badly she'd screwed things up.
A soft knock at her door brought a frown to Kate's face. Who was visiting her at this hour? She rose from her couch, grabbing her gun and hiding it behind her back. Thunder roared outside as she unchained the latch and pulled the door open, her heart stopping once she saw the man standing at her threshold.
"Castle." She swallowed hard. "What do you want?"
Castle's blue eyes weren't nearly as bright as they had been the last time she saw him. His shoulders slumped, and his hair was wet from the storm that had just started. He sucked in a deep breath, the stubble on his cheeks making him appear far older than he actually was.
When he spoke, Kate thought she smelled alcohol on his breath.
"You."
"You're drunk," Kate countered, her first instinct to protect herself as she went to shut the door. But he placed his foot against it, and the door wouldn't budge.
"No, I'm not." Castle took one step forward. "My head's as clear as it's been in months."
Kate's eyes narrowed. "Stacy know you're here?"
Castle deflated further at the mention of his fiancée, averting his gaze with a sigh. But his eyes bore into hers again, and the writer straightened his posture, opening his right hand to show the engagement ring resting in his palm.
"Stacy's not around anymore."
"Rick," Kate was borderline speechless, shaking her head even as her pulse quickened. "Please don't tell me you dumped her the night before your wedding."
"She dumped me," Castle said matter-of-factly.
Though her heart broke for him, Kate had to admit a selfish part of herself was glad to hear the news. If the look in Castle's eyes was any indication, he wasn't entirely broken up by the news, which made the detective wonder why he was marrying her in the first place.
"I'm sorry," Kate lied.
"I'm not." Castle gently pushed his way into Kate's apartment, pocketing the ring before turning to meet her gaze. "I just…I had to see you again, Kate. I had to…" He shook his head. "I needed you to know."
Kate took a tentative step toward her ex. "Need me to know what?"
"That the day I broke up with you was the day I made the worst mistake of my life," he admitted, tears brimming in his eyes. "Whatever happens from now on, I need you to know how sorry I am."
"No," Kate sighed, placing a tentative hand on Castle's arm. When he didn't recoil, she grabbed the lapels of his coat and looked up into his eyes. "I'm the one who's sorry. I should've been honest with you from the start." She shook her head and glanced at the floor, her voice cracking. "If I did, I might've had something to come home to."
His hands rested on Kate's shoulders, and when the detective glanced up at Castle again, he brushed a tear off of her cheek. "I've never stopped loving you, Beckett." His voice was almost a whisper at this point. "That's why Stacy left. She knew I wasn't over you yet. She knew I probably wouldn't ever be over you."
"Rick…"
"Let me finish." Castle's hands cradled Kate's face now, some of the color starting to return to his eyes. "I've known for three months, that you were back. And every day, I've picked up the phone and almost called."
"Why didn't you?"
"Fear," he shrugged. "Pride. Worried that nothing could be salvaged. Kate…" A tear rolled down Castle's cheek, and his right thumb brushed back and forth over Kate's cheek. "I don't know if we can get back what we had, but…I couldn't live with myself if I didn't try. You asked me what I want, Kate, and the answer is you. I just want you."
Kate felt the tears running down her face and did nothing to stop them. "Rick…"
"I'll understand if you say no, Kate, and I deserve that," Castle shook his head. "But Stacy was right. You're my one-and-done, Kate. If my third time's gonna be the charm, I want it to be with you."
Unable to find the words and kicking the front door shut behind her, Kate leaned in and kissed Castle, slow and tentatively at first, only to deepen the kiss once Castle's broad arms wrapped around her shoulders. Her eyes fell shut, tears still running down her face, their lips finding their familiar station against each other.
They were both crying as they made out, Kate's back now pressed against the door. Another rumble of thunder announced its presence, accompanied by a flash of lightning as the downpour really started. It was like that fateful night in so many ways, and as Castle grabbed Kate's hand to lead her into the bedroom, their eyes locked on each other, he hoped this one would be more permanent.
Castle had never been so happy to be dumped.
