A/N: personal update: I'm currently in the process of moving to Spain for two months (I'm from England) and so life is pretty hectic right now, but I promise I won't abandon this story and will try and get the final few chapters up ASAP! Thank you!

"Mr Smith?" Beckett called as she banged on the door. "This is detective Kate Beckett with the NYPD, I need you to open the door." Nothing. Nobody answered, they couldn't even hear anybody moving inside the apartment but she tried again, louder this time.

"Beckett," Castle said, "I really don't think he's in. Why don't we go back to the precinct and try again later?"

"He might not be there but the package could be," she replied, stepping a few paces away from the door in preparation to barge through. "Stand back," she warned.

"No..Beckett, wait," Castle said, gripping her upper arm firmly. "You can't just go breaking into people's apartments! I mean, I know I'm all for knocking doors down and sneaking around but you've got nothing that proves Smith has this package in the apartment, what if someone calls the cops?"

"I am the cops, Castle," she reminded him.

Dammit, she was stubborn when she wanted something. Okay, think, he told himself, what would stop her from doing this? "Okay fine," he relented. "Have it your way - break down the door and then when the cops come, I'll leave it to you to do the talking, okay?"

He could see the hesitation in her eyes, a hesitation almost hidden by the steely determination he'd seen there so many times before. He had her and he knew it. "Fine," she sighed. "But we're not leaving, we'll sit in the car and watch for a while, see if he comes back."

It was a compromise but given how proud of himself he was at having got her to back down, it was a compromise he was willing to take.

They sat in a comfortable silence in the car, the kind of silence that wasn't awkward when you knew the other person so well and were both just happy to sit and think for a while. Beckett had text the boys on the way back to the car and given them an update, also asking them to keep her and Castle informed of any developments they might have with Maddox.

It was about ten minutes later when Castle broke the silence. "You left," he said simply, as if only now realising what had happened.

Beckett hesitated for a minute. She had been dreading this conversation coming up, the moment Castle put aside his joy that she was in love with him for a moment and actually thought about how it had all played out. "I had to," she whispered. "I just can't leave my moms case alone. I wish I could..oh god you have no idea how much I wish I was strong enough to walk away from it all and let it carry on with my interference but I can't."

"You're wrong," he replied. "About not being strong enough. You're the strongest person I know and I mean that as a compliment. I would never, ever ask you to choose me over your moms case, I know how badly you want this but I can't sit here and say it didn't hurt when you left LA."

"I had to," she repeated. "Gates called me and..I don't know I just knew I had to come back. I didn't want to, I can promise you that I never wanted to leave you but this..thirteen years, Castle." She looked up at him, eyes begging him to understand why she'd done what she had. "Thirteen years of being brushed off by the investigating detective, of it being passed off as random gang violence. Thirteen years of heartache and pain and suffering, of having no one to turn to when my dad chose the bottle over his only daughter. Of endless nights down in the archives at the the precinct, scouring the pages of her case file, desperate to find something someone had missed..and all it took to see the smallest ray of light was you, interfering and poking your nose in where it wasn't wanted but look how far you've got us, Castle."

"Yeah, and now we have nothing," he said, stretching the truth just a little for dramatisation. They didn't exactly have nothing but it sounded a lot better for his argument than saying they might have something when Smith got home. "We're sat in your car outside the apartment of a man we know nothing about when all you had to do was say no, I'm not going back to that. You just said yourself that it's been thirteen years of heartache and pain and yet you willingly came back to it!" Castle didn't even know why he was so angry, he meant what he'd said, that he would never ask her to choose him over her mothers case but he still failed to understand why she kept going back when there was no promise of a solution. So many times in the four years he'd known her had they thought they'd got close only to have it ripped away again and yet here they were, back at square one.

"You didn't have to come back, you know," she shot back coldly. "If you don't want to be a part of this then there's nothing stopping you from going back to California and forgetting all about this case. I understand," she lied, "it's not easy and at the end of the day, it's not your mother - why would you want to sit around doing this for someone you didn't even know?" The words were harsh and completely unnecessary - not to mention the complete opposite of the man she was saying them to. But she was angry, more at the case than at Castle but as usual, he was the one she took her anger out on.

"Is that really what you think?" He asked. "You honestly think I don't care about what happens because I didn't know your mother? I may not have known her but if her daughter is anything to go by then she must have been a pretty remarkable woman." How could she sit there and say that? It had been him that had reopened the investigation in the first place and now she was pushing him away again?

"No, that's not what I think," she sighed, running her hands through her hair. "Because you are one of the kindest, sweetest, most genuine people I have ever met and I know that even know you didn't know my mom, you're doing this anyway, because you want to." She didn't deserve him, that was being made abundantly clear right now but she was selfish, she didn't care that she didn't deserve him, she wanted him anyway. "Without you..we wouldn't be here and I'm sorry, okay, I really am sorry that we've come so close so many times only to have it all slip away again but I can't walk away from this. I won't stop you from leaving because I can't force you to be in this with me but please, Castle, don't make me do this on my own."

Castle was about to reply when he caught sight of something out of the corner of his eye. Glancing up, he realised it was who they en're here to see. "There's Smith," he said, moving to get out of the car. Looking back, he realised Beckett hadn't moved. "What are you doing?" He asked, "I thought we were here to see Smith?"

"We are," she said. "But he will still be there tomorrow and the next day, I'm not getting out of this car until I know you understand why I had to leave California." I took everything she had to make herself stay in that car but Castle meant so much to her, she wouldn't ruin everything again for a man who may or may not be able to help them. And he was going inside his apartment, they'd see if he left again. She'd waited thirteen years, five more minutes wouldn't kill her.

It was in that moment, as Castle was half in and half out of the car that he realised something - he understood why she had come back, because right now, he wanted the son of a bitch who had taken Beckett's mother from her just as much as Beckett herself did.

"I get it," he admitted. "I get why this means so much to you. I meant what I said about how knowing you makes me realise how incredible your mother must have been, she raised an amazing daughter and right now, I want justice for her too."

Beckett could have cried. She could have potentially been faced with the hardest decision of her life, choosing Castle or her mothers case but she needed him to understand, he'd been there for the biggest developments they'd had so far and she honestly couldn't do it without him.

"So does that mean we can go and talk to Smith now?" Castle asked.

"Yeah," Beckett smiled. "Let's go."

The two of them hurried back across the road and into the apartment block and up the stairs, they didn't have time to wait for the elevator to arrive. They'd just reached the door to Smith's apartment when they heard shouting.

"Who the hell are you?" Came a voice that was probably Smtih. "Get out of my apartment before I call the police!" The other voice was speaking too quietly for either of them to hear, but Smith didn't lower his volume. "I don't know what you're talking about, I have nothing that you could possibly be looking for. Now leave!"

Beckett knocked on the door, hoping interrupting would startle the intruder into leaving or something. "Mr Smith," she called. "Can you open up, please?"

They waited a few moments but everything was quiet, which was strange given that he had been making quite a lot of noise not long ago. "Can I break the door down now?" She muttered to Castle, not waiting for an answer before she pushed her way inside. She pulled her gun out and positioned it in front of her as she walked into the apartment slowly, looking for Smith and the intruder. Smith was in the living room - lying on the floor with a pool of blood oozing from his side. "Castle!" She gasped. "Call an ambulance!" After checking the room was safe, she knelt down next to him and felt for a pulse. "He's alive," she mumbled. "Mr Smith? Can you hear me?" The rest of the apartment was empty and the large bay window was wide open - the intruder must have left using the fire escape.

Smith half opened his eyes, gasping for breath before realising who was in front of him. "Maddox.." He groaned. "Was here. Not..safe..package.." And then his eyes closed.

Once the paramedics had rushed Smith into hospital, Castle and Beckett were about to have a quick look around, see if they could find the package Montogmery had sent to Smith when Beckett's cell phone rang. "It's Esposito," she said before answering. "Hey Espo, what's up?"

"I think you guys need to come back here," he said, "there's been an explosion on Markwell Street and it turns out Smith owns the building."

"That's not good," Castle said when Beckett relayed the information to him. "Do you think it's Maddox?"

"Only one way to find out," she said, heading to the crime scene and not to the precinct. The bastard deserved everything that was coming to him.

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