A/N: This is set after Changes for the Dresden Files, and I wrote this after watching episode 9 of season 3 of Castle.

This was written just for fun, and I don't own anything.

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Castle watched as Kate Beckett chewed on her thumb nail thoughtfully whilst looking through the two-way mirror glass. Inside the adjoining room was a short, blonde woman. Her file said she had been a Lieutenant in the Chicago Police Department, in charge of the Special Investigations. She'd turned the department around. Solved a lot of cases. And, apparently, hired a wizard to consult for her on a good portion of them.

She had later been demoted to Sergeant. And now, had "retired."

When she had been arrested, she had come quietly.

"She's cute." Said Castle, who was, as ever, standing by Kate's side. Kate turned to him slightly, raiding an eyebrow.

"She's a sharpshooter and a master at aikido. Been practising since she was four." She said.

"Yeah, but she's kind of… adorable."

"Maybe."

"Jealous, much? Don't worry, Beckket, I don't fancy following around a disgraced cop just yet."

"Oh, funny." Kate said and then walked to the door. "Coming?"

Castle gave a short nod, and followed her into the room that held the short ex-cop. She turned slightly to watch them come in and sit down. She looked annoyed. Like they were holding her up from an important meeting.

"Hello, I'm Detective Kate Beckket." Kate said as she sat down. "Fancy telling us what you were doing standing over Mr Montgomary's body when we found you?"

"Hello, Detective. I'm Karrin Murphy, let's try and get this over with quickly. I didn't kill Montgomary, I have an alibi. Your coroner will be able to come in and tell you that he was died a few good hours before I got there, which was only about 15 minutes before you got there. You can check the security footage."

"What were you doing standing over the body?" Said Castle, repeating Beckett's words. He stared intently at the ex-cop; she had bags under her eyes, as if she hadn't slept in a long time.

"I had been planning on meeting him. Like I said, he was already dead when I got there, Mr…?" Answered Murphy, giving Castle a pointed glance.

"Richard Castle."

"Oh! The writer, that's right, Dresden quoted you constantly when he was going through his detective phase…" Murphy trailed off. Her cute, face slightly drooped.

"Dresden?" Asked Castle, he was half tempted to give the woman a hug. She looked like she desperately needed one, and she was the same height as Alexis.

Beckket turned to him and quickly murmured, "the Wizard."

"Yes, the wizard. " Murphy said, her lips twitching into a smile slightly. "He advised me, like I'm guessing you advise the detective here? You have a similar… Dynamic."

"The wizard. He died recently, didn't he?" Castle asked gently. "Your file says you guys grew close. Says you risked your job multiple times for him. Montgomary was known for dealing in shady stuff, and your friend died by what seemed to be a professional hit. I'm thinking you found something linking him to Dresden's death…"

Beckett picked up on where he was going, "Dresden was a good guy – helped the cops. Was even your friend. It'd be understandable that you'd want the killer brought to justice. But Montgomary was nearly untouchable by the law. You then retired from SI – you didn't want the dirt of what you were about to do to touch your unit."

"Did you decide that since you couldn't touch him through normal means, to hunt him down in New York? And when you did find him, you decided to deal out justice." Castle said; following on Beckett's words as easily as she did his. "Going from good cop to bad cop for the revenge of your fallen partner in crime-fighting? Well and truly understandable."

"A little cliché, but a good story." Replied Murphy, but Castle noticed that her eyes looked a little teary. She gave a sort of half-smile to him, "you're almost close, though."

She then turned to Kate, "Detective, I want to help you. I've been where you are. But my current guess is that Dresden's killer was Montgomary's." Murphy sighed out, and began looking rather fixedly at the wall behind Kate. "If that's true, you're going to have to collaborate with the Chicago PD. I'd advise chasing up what they know. Unfortunately, I don't think you'll find the killer."

"And why's that, Karrin?" Kate asked gently. Castle had heard that tone before, and it had made hardened criminals break before.

"They're playing in a whole other league. You're out of depth. If you're anything like me, I know that you won't just take my word for it. But I feel I need to give you fair warning. Now once you let me go, I'm sorry to tell you be hearing from me."

"What do you mean, Karrin? If you tell us, we can help you." Kate said, insistently.

"I know all the tricks, detective. And believe me; I have personally done what you're doing now." Murphy said her hands were slightly trembling. "But I am looking for Dresden's killer, and he mixed with a different and dangerous lot. But I will find the killer. But I will also turn that killer into the appropriate legal authority. I'm a cop at heart, detective, just the same as you. And just like me, I don't think you would stop looking if someone killed someone close to you, like a family member. Or even your partner, castle here. Tell me honestly what you would do if someone killed him?"

Out of the corner of his eyes, he saw Kate's mouth opened and shut. She glanced down for a moment. His stomach tired itself in a knot, as he wondered what he'd do if she was killed.

"Just what I thought. I really don't want to cause trouble for you detective, but I will leave here. I can't afford to waste much more time."

"Karrin." Castle said, causing the blonde to look up sharply, "Detective Beckett and I have looked into people who thought they were vampires, people obsessed with steam-punk, came across folks who pay money to pretend to be spies, and dealt with alien conspiracy theorists. And the majority of them have been really nice people. We're not judging you or Dresden. Just tell us what sort of dangerous people he was involved with; did someone intend to harm him?"

Murphy's mouth twitched into a smile slightly. "Someone want to hurt Dresden? Only everyone he met. That's why it's taking me so long. The guy did not know when to shut up, I swear."

"I know the feeling." Said Kate, with an amused smile only for it to quickly vanish, "Karrin, you're all but admitting to the fact you intend to go out, hunt someone down, and kill them."

"Not necessarily. I said I'd bring them to justice. I've said this already. I'm a cop at heart. I understand your position, and I hope you understand mine."

Kate's frustrated sigh at Murphy's declaration was cut short by her mobile ringing. Castle watched as she stood up, walked to the dorm and stood outside the room to answer the call.

"Beckett." She said tersely, and then paused for a moment to listen to the speaker on the other end. She looked pointedly at Castle, "her alibi checks out." Kate started walking towards Laine's, still on the phone.

Richard Castle stood up to follow her.

"Castle?" Murphy said softly, Castle turned to look at the small ex-cop. Her eyes were still slightly wet. Like she was on the edge of tears, but the set in her jaw indicated she wasn't about to let herself cry anytime soon. "How'd you get on her team? And why?"

"Connections with the Mayor," Castle said with a smirk, before he could stop himself.

"Hmm. You love her." Murphy stated, like it was a well-known fact. "Oh please, don't pull that face."

Castle slightly inclined his head. Not that it mattered. Kate hadn't shown any indication that anything more than a strange-sort of friendship was returned.

"Don't let her get away. You'll never forgive yourself if you do. And she needs someone kind of goofy to balance her out, that's how it was with…" Murphy trailed off, and got up. She gave Castle a quick pat on the arm, and started to leave the room.

"You can't-"

"She loves you too. And I hope to god that she says it in time. Just don't let her go." And with that, Murphy left the New York Police Department. And true to her word, Castle and Beckett never saw her again, they never caught the killer and they one day did admit it to each other.

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Thank you for reading. I will love and cherish all reviews.