Author's Note: The funny thing about this crossover... at first, I wasn't sure how it would all fit. Yeah, the idea of Kate Beckett, vampire slayer *sounded* cool, but I wasn't really sure how the execution would work. This has been so much more fun and more intense than I could've imagined, and I hope you are enjoying the ride as much as me. Leave a review if so!

Angel Investigations…

As soon as Angel walked back into his office, he pulled the mini cassette out of his coat before shedding the garment and tossing it onto the leather sofa in the corner. He lowered himself into his swivel chair with an exhausted sigh, staring at the device in his hands. Curiosity was still eating at him; he had decided that he would give the tape to Kate, let her figure out what was on it rather than poking around himself.

But still, it was tempting.

Opening the drawer, Angel tossed the cassette in and shut it. He wasn't going to go investigating behind Kate's back anymore. Any hope of romantic reconciliation on their part was gone - thanks at least in part to a meddlesome but incredibly loyal mystery writer - but Faith had been right when she challenged his desire to get answers on his own.

Angel still wanted to know who killed Johanna Beckett - and why - but he had learned that he was better off letting Kate tackle that personal hurdle. His own selfish curiosities had meant the demise of their relationship, but he was still fond of her.

The lights came on and before Angel could react, he felt the prick of a crossbow aimed at his neck. He looked up to see Lilah Morgan standing over him, a dark smirk on her face. Tearing his glance away from her, Angel saw Lindsey McDonald emerge from the shadows. It took all the restraint the vampire had not to ball his hands into fists.

Instead, Angel kept as still as he could, even as his jaw clenched.

"Hello, Angel."

"Lilah."

"Just like old times." The sneer on Lindsey was the same one he used to wear in L.A., and Angel's desire to smack it clear off his face was no less intense after all these years. Then again, what was one decade to someone who had been alive for almost three centuries?

"How'd they rope you back in, Lindsey?" Angel's eyes narrowed. "Same clause in your contract as Lilah? Bet the Senior Partners pay extra special attention to you after what you did in L.A."

"We want everything you have on Johanna Beckett's murder," Lindsey replied.

"I have no idea what you're talking about."

Angel flinched when Lilah dug the tip of the arrow a little bit harder against his neck. She probably wouldn't kill him if she pulled the trigger – chances were a simple arrow wouldn't decapitate him – but the newfound ferocity in her eyes told Angel she would pull the trigger in a heartbeat. Something he wasn't sure he could've said about her toward the end of her tenure in Los Angeles.

"Then I guess you don't know anything about the file on your monitor." Lindsey quirked a brow. "Or the notes you've got jotted on a pad downstairs."

"I'm sure the NYPD would be glad to know you've broken into my property."

"And I'm sure they'd be glad to know you have photocopies of official NYPD case files hidden away in your basement." Lindsey approached the desk and placed a hand on Lilah's shoulder; reluctantly, she lowered the crossbow. "Did Detective Beckett give you that file? Hm? I mean, I know you two were chummy for a while, but… sharing official NYPD documents? Can't imagine One PP would like that."

"Unless the fact that they're letting a novelist follow her around means they're really relaxing their policies," Lilah added.

Angel's eyes flicked back and forth between the two lawyers. "What's your interest in Richard Castle?"

Lindsey shrugged. "Aside from Gina Cowell's bank account, there is none. We're focused on Detective Beckett."

"And why is that?"

"I could ask you the same thing." Lindsey sat at the edge of the desk, leaning in until his face hovered inches away from Angel's. "Does she know you're still poking around Johanna's case?"

"What's your interest in Johanna Beckett?"

Lindsey shrugged in disinterest, even as the look on his face betrayed him. "Why would we be interested in a civil rights attorney who's been dead for the last… how long has it been?" Lindsey shook his head and smirked. "As brilliant a legal mind as the city of New York ever saw, yet she was still dumb enough to slip into an alley by herself in the dead of night. From my experience, her daughter's just as reckless."

Angel's nostrils flared as he grit his teeth. "You leave Kate alone…"

Lindsey's eyes narrowed. "Weren't you friendly with another cop named Kate once? How'd that work out for you?"

Before either lawyer could register what had happened, Angel leapt from his chair and came up to them from behind. He grabbed both Lindsey and Lilah by their respective necks as his face morphed into the disgusting mask of the undead, fangs teasingly close to the side of Lilah's neck. Both lawyers froze, but they gave no outward show of fear.

They were bolder than Angel remembered.

"Maybe I wasn't clear the first time," Angel growled. "I catch either one of you sniffing around Detective Beckett, Wolfram & Hart's gonna be short two lawyers again."

Angel released his grip on Lilah to grab the crossbow from her grasp, spinning her around and pointing the weapon at her neck. He kept his other hand wrapped around Lindsey's neck, tightly enough that the other lawyer was gasping for breath. The vampire was hoping for either of them to make a move, to give him a reason to finish them off.

Logically, Angel knew that wouldn't mean the end of them - Wolfram & Hart didn't work that way - but right now, a little violence was just the release he needed. Lindsey and Lilah were just convenient targets.

"Alright." Lilah nodded once, exhaling when Angel lowered the crossbow and released Lindsey. "Have it your way, Angel."

The two lawyers composed themselves and wandered to the office's exit. Lilah left the office, but Lindsey held back, failing to suppress a smirk and grabbing the door frame. The lawyer's smile only grew when he looked up and saw Angel still snarling at him with yellow, feral eyes.

"Oh, and, uh…" Lindsey chuckled to himself, "Spike sends his best."

Castle's loft…

"I'm sorry," Castle shook his head and grabbed the scotch bottle, uncorking it and taking a swig. This was no longer a pour-drinks-into-a-glass kind of night. "You lost me, Rupert. You mean to tell me all of this goes back to Beckett's mother?"

"More or less," Giles affirmed. "Johanna was an informant for the Council."

Castle took another swig before capping the bottle and sliding it across his desk to Giles. "I thought Johanna was a lawyer."

Giles shrugged and took a swig of his own. "The same way I used to be a high school librarian."

A disbelieving smirk passed through Castle's lips, and in the moment, he was acutely aware of the stubble grown into his cheeks. It had been one hell of a day in a long line of days that were hard to believe - even for his overactive imagination. Castle made his living in the fantastical, but this was far from anything he could ever conjure up onto the page.

"Next thing you'll be telling me you Watchers were spies for the Queen." Castle shook his head and he couldn't help the rueful smile on his face. "You weren't Agent 007 by any chance, were you?"

"No." Giles chuckled and shook his head. "Not near handsome enough, I'm afraid."

Hurried footsteps descending the staircase caught Castle's attention, and he glanced at the clock to notice that it was almost 6:30 in the morning. Castle looked up to see his daughter bound into the room with far more energy than the hour allowed, throwing her arms around Giles with an excited squeal.

"Uncle Rupert!" she exclaimed as Giles' arms wrapped around her.

"Dear lord, Alexis!" Giles shook his head and tightened the hug. "You're practically a grown-up now!"

"Don't remind me," Castle muttered under his breath.

"What brings you to New York?" Alexis asked with a crooked brow once the hug ended.

"Work," Giles answered, throwing a glance Castle's way. "I figured I would stop by, see an old friend… congratulate him on his latest book."

Alexis frowned. "At… six in the morning?"

"Yes, well," Giles chuckled, "I'm afraid I'm still operating on London time."

"Are you staying long?"

"As long as the job requires," Giles was being cryptic, clearly trying to shield Alexis from whatever was going on. He exchanged another glance with Castle before the redhead's hand on his shoulder caught his attention.

"Well, I have to get ready to go to school," Alexis lamented. "Maybe we can catch up when I get home?"

"Yes, that would be lovely." Giles smiled. "I'll make us a spot of tea."

The young redhead pulled Giles into another quick hug before leaving her father's office and heading back up the stairs. Rupert, smiling, removed his glasses and lowered himself into the outrageously soft chair again.

"Your daughter has grown into quite the remarkable young woman, Richard."

"Tell me about it," Castle said with a wistful smile - one that disappeared as soon as he heard the front door to his loft open and shut. The sun was starting to rise, rays spilling out in between the high rises of SoHo and starting to illuminate his office in strips. Castle had been awake for almost twenty-four hours by this point, but any exhaustion he felt melted away when he saw Kate stride from the door and into his office.

Castle barely had time to register how red her eyes were before Kate was standing right in front of him, wrapping her arms around his broad shoulders and burying her face in the nape of his neck. When she was wearing her heels, Kate Beckett wasn't that much shorter than Castle. Once the shock of the contact wore off - Kate never touched Castle aside from ear-twisting or nose-pinching - he enveloped the detective in his arms and gave her a comforting squeeze.

Castle and Giles locked eyes as Kate began to softly cry into the writer's shoulder. His hand rubbed up and down the small of her back as softly and smoothly as possible, but she didn't appear to be calming. Giles was the first to break eye contact, focusing on a spot on the floor as he, yet again, removed his glasses.

"I'm so sorry, Kate," Castle whispered, feeling the burn of emotion in his own eyes.

Her fingers clutched into Castle's shirt, which was wrinkled from a full day's wear. Castle gave her another squeeze, and he could feel a damp spot forming near his collar. Kate whispered something into the fabric of his shirt, something he couldn't make out, and Castle gently pulled out of the hug to hold onto Kate's shoulders.

"Beckett," he said softly. "Kate… are you with me?"

With a sniffle, and a wipe of the back of her hand against her cheek, Kate nodded. "It was Spike," she said through a cracking voice, shaking her head. "He… he walked into the precinct and just… went off."

Castle clenched his jaw. "Is everyone else alright?"

"He killed two other officers," Kate began, pausing to swallow back another sob. "Broke Ryan's wrist and gave Espo a concussion." The detective looked up, her worn eyes locking with Castle's. "Montgomery was found dead on my desk, my letter opener had been jabbed into his neck. And there was a note."

"What did the note say?"

A soft upper-crest British voice broke the moment, and Kate glanced at Castle in confusion before turning around. With another sniffle, Kate swiped at her eyes again as her brows furrowed. "Who are you?"

"Rupert Giles," the older man stood and placed his glasses back on his face.

"Last I saw Buffy, she was at the precinct," Kate muttered, glancing back and forth between the two men, as if she were imploring Castle to provide some answers.

"I'm here to see you, actually."

"Me?" Kate shook her head. "Castle, what's going on?"

"Beckett," Castle gave Kate's shoulders a squeeze, "what did that note say?"

"It read, 'Sorry about your captain, love. It should've been you. William sends his regards'."

Giles sighed and began pacing. "I was afraid of that."

Kate's frown deepened. "Afraid of what? And who's William?"

Giles picked up the file folder that had been resting, unopened, on Castle's desk. Handing the folder to Kate, Rupert fixed her with a sympathetic gaze and a single nod. "Katherine, I have reason to believe your captain's death is related in some way to Johanna Beckett's murder."

Taking the folder, but not opening it, Kate stared at Giles with a mixture of fury and confusion in her eyes. "How do you know about my mother?"

"Your mother was once a close personal friend, Detective."