A/N: I wrote this awhile ago and forgot about it haha. I was looking through all the stories and stuff saved on my computer and I found it and decided to post it. It's sorta AU, but I hope you like it anyway! Reviews are appreciated! :)

Disclaimer: Castle's not mine!

It had taken two months. There had been tons of sleepless nights and incredibly short tempers, all mixed together with a heavy reliance on coffee to keep them all going. They had hit numerous dead ends, and gone back to search for something they hadn't seen before. It wasn't until they found the missing person file for a young woman, Melody Turner, that they had finally gained some leeway.

And that's how they found him, the serial killer who murdered many women, including Detective Kate Beckett's mother. They had found him, but sadly, it was too late for Melody. They had arrived moments too late, and she had died.

They were at the house now. Melody was brought out in a body bag while Castle and Beckett watched the killer being handcuffed and forced into a cop car.

Castle heard Kate's deep breath and gently wrapped his arm around her back. "It's over." He said quietly.

Beckett's eyes were glued to the cop car that held her mother's murderer. A lump formed in her throat as she thought of that night, and how that man sitting calmly in the car had torn her life apart. "Yeah." She agreed, working hard to speak through the lump in her throat. Her voice came out shaky.

"You okay?" Castle asked gently. His arm seemed to tighten around her and Kate let herself lean into him. She took a shaky breath.

"I'm fine." She swallowed. "I just wish…maybe if we would have been here a little sooner then maybe…maybe Melody would still be alive." Kate bit her lip, trying desperately not to cry. "If I wouldn't have taken so long looking at that damn report then maybe she wouldn't have died too."

"Don't do this to yourself, Kate." Castle said. He moved around her so that they were facing each other, and he placed his hand on the side of her cheek. "There was no way to save her. There was nothing that we could do for her besides arrest the killer. He's going to pay for what he did to Melody and your mom, plus all of the other women."

"But maybe if I—,"

"There wasn't anything you could do." Castle spoke quietly, looking directly into her eyes. "The important thing is that he's finally caught. No one else has to suffer because of him."

A tear trailed slowly down Kate's cheek.

"Thank you, Castle." Beckett's voice was quiet, and Castle hated seeing her upset. But he knew it was to be expected. After spending so long torturing herself by trying to solve her mother's murder, and after having therapy, it was expected that Kate would be emotional when they finally caught the killer. "We would've never caught him if it wasn't for you. I owe you."

Castle smiled. "It's what I'm here for. And you don't owe me much, just a lifetime of servitude."

"Oh, is that it?" Kate said sarcastically, letting her lips curve into a smile. She wiped her tears away with the sleeve of her jacket. "Let's get out of here. Knowing that he lived here all that time, right under my nose, and I had no idea, is killing me."

"But at least we got him."

Castle wrapped his arm around her and together they walked towards the car.

A/N: I'm really not sure how this turned out...I don't like the ending, haha, but I can't think of any other way to end it. If anyone needs clarification on anything feel free to PM me or leave a question in a review. Which reminds me, please review :) Thanks!