Author's Note: Thank you so much for the kind words and the support so far; I'm having such a blast combining my two favorite TV universes, and the real fun is just beginning! Please continue reading and reviewing!

Midtown…

As soon as Detective Kate Beckett killed the engine of her police-issued Crown Vic, Richard Castle reached for the handle on the passenger's side door – only stopping once he felt Kate's hand tugging on his left shoulder.

With a half-quizzical, half-amused smirk, Castle regarded his reluctant partner. "Yes, Detective?"

"If you're really going to be shadowing me," Kate said, barely trying to hide the disdain in her voice, "two rules. One: you do as I say, when I say – including now, when I tell you to stay in the car."

Castle's face fell into one of disappointment, and he opened his mouth to speak before Kate tugged on his shoulder again. "And two: You are shadowing Detective Beckett, not Kate the Slayer…got it?"

His eyes flickered to the back seat before Castle regarded the detective eyeing him suspiciously and nodding. He watched Kate's brows arch in suspicion, and for a moment, he wondered if this was how suspects felt whenever she had them in the box.

When Castle still didn't speak, Kate cleared her throat. "Well…?"

"Yeah." Castle deflated into his seat, letting go of his grip on the seat belt. "Yeah, I got it."

"Good." Kate glanced into the rearview mirror as she opened the driver's side door. "Make sure he doesn't go anywhere."

When the driver's side door shut, Castle glanced over his shoulder into the back seat where Faith Lehane sat. They shared a shrug and a glance of amusement, waiting until the trunk slammed shut. Castle watched Kate join the rest of her crew, fastening the bulletproof vest over her chest before unbuckling his seat belt and turning to face the dark-haired woman.

"Is she always like that?"

Faith shrugged. "Don't ask me. I just met her."

"So what's your story?" Castle cocked his head to the side with an arched brow.

"Oh, we so do not have time for that," Faith answered, raking her fingers through her brown locks. "Unless you're gonna write a book about me, too."

Castle made an exaggerated gesture of resting his chin in the palm of his hand, his elbow resting on the center console in the Crown Vic as his eyebrows arched and his blue eyes widened. "Tell me a good enough story and I just might."

Faith smirked and shook her head. This guy was nothing more than a giant kid, but damn, he was fun. Her dark eyes regarded his, before she sat up a little straighter and rested her elbows on her knees.

"Did you know you're talking to a convicted murderer?"

The writer's gasp was audible, and Faith couldn't help but smirk. "Really?" Castle cocked his head to the side before glancing over his shoulder. "That explains the stink eye she gives you. But what about me?"

Faith shrugged again, glancing out the passenger's side window in time to see the ESU unit busting down the door, Kate bursting through with Detectives Ryan and Esposito in tow, the three of them with their weapons drawn. Their shouts of NYPD! and Freeze! were muffled through the glass, but the barrage of gunfire was unmistakable.

"You ask me," Faith said, nonplussed at all the racket. "Detective B could use a little fun in her life. Someone's wound a little too tightly around their stake."

His eyes glued to the open door, desperate to know what was going on in there – especially once the gunfire died down – Castle shook his head. "Sound like you know the type."

"I've had experience."

A loud roar, guttural and unlike anything Castle had ever heard before, interrupted the conversation, and before he could react, Ryan and Esposito burst through the threshold, glancing over their shoulders as they ran back to their squad car – a candy apple red Dodge Charger – diving behind it and huddling together.

The roar returned, at which point Faith pushed her way out of the car, grabbing a seven-inch long dagger that had been hidden under the waistband of her pants. By the time Faith disappeared through the door, Castle pushed himself out the car as well to follow. After all, if the woman charged with keeping him in the car left said car, then why did he have to stay?

His answer came when he got to the doorway, watching Kate cradling her service piece in both hands as Faith brandished the dagger. Hovering over the two women was easily the most foul creature Castle had ever seen – certainly more disgusting than the vampire that had attacked him the other night.

This monstrosity was at least ten feet tall, its skin a mix of olive green and shit brown, a viscous substance covering its skin. Tusks sprang from the creature's nostrils, and its menacing growl sounded like a cross between a wounded hyena and a pig squealing in a pool of mud.

Castle wished he had a camera; his poker buddies were never going to believe this.

"Holy shit!"

His expression caught the attention of not just Kate and Faith, but the creature as well. Two pairs of human eyes trained on the writer, as did the four orbs on the monster's forehead that he guessed were its eyes. The roar returned, louder than before, and the creature pushed its way past the Slayers toward Castle.

"Dammit, Castle!" Kate sprang back to her feet, making an impossible leap onto the creature's shoulders – a move made all the more impressive given the heels she was wearing. Faith was in her tracks, deciding to take the creature low, plunging her dagger into its right leg. The howl of pain was stomach-churning, as was the mustard-yellow ooze pouring from the wound.

Castle covered his mouth as he backed away, fearful he would lose his lunch. He watched Faith pull the dagger out and stab the monster again, even as Kate discharged her weapon into the back of what Castle guessed was its neck. The monster lurched forward with a grunt, falling face-first onto the cold floor leading out the door.

Castle felt the ground shake when the monster landed, losing his footing and falling on his ass. He looked up again just in time to see Faith jab her dagger into the back of the demon's head, more of that yellow gunk erupting until the monster lay motionless and silent.

The two women exchanged a glance, catching their breath before Kate holstered her weapon and approached Castle.

"What did I tell you about staying in the car?!"

"I was following her!" Castle protested, pointing at Faith – who just shook her head when Kate shot her an accusatory glare. "And I just say…that was so cool! I mean, I might throw up later, because that's disgusting, but…so cool!"

"Glad you're entertained," Kate deadpanned with an eye roll. "See how entertaining it is when one of those things kills you."

"Yeah, right," Castle scoffed as he stumbled back to his feet, tailing the two women who were now heading back to the Crown Vic. "I'm following two kickass women who fight demons for a living, how dangerous can it be?"

Kate stopped on a dime, twirling back around to jab her finger into Castle's chest. He tried not to cringe at the pain, but he had to admit it really hurt. "Remember when I told you that you were shadowing Detective Beckett and not Kate the Slayer?" She didn't even give Castle a chance to reply. "That's why. This is dangerous, Castle."

Castle shrugged. "But I signed a waiver."

"With the NYPD," Kate countered. "This is different."

By the time the trio had gotten back in the car, and Kate cranked the engine before snagging a few napkins from the glove box to wipe the demon blood spatter that had gotten onto her face, she glanced in the rearview at Faith.

"Look, Castle," she said. "I'm only letting you tag along because my boss, my boss' boss, and his boss said so. But if you keep poking around in my slaying, then this little arrangement is over."

Seemingly nonplussed, Castle shrugged. "Then I'll just start shadowing Faith."

Ignoring the jab, Kate glanced into the rearview mirror again. "I'd like to know what that thing was," she said. "And if I gotta worry about there being more of them."

"Already on it," the other Slayer said. "Took a pic of it after we killed it, shot it off to G-man over in England. Should hear back in a few hours."

"Good." A teasing grin played across Kate's face. "Glad someone in this car's helpful."

Lilah Morgan's office…

"I have to say," Lilah Morgan took a seat in her plush leather chair, the Manhattan skyline behind her thanks to the view of her 45th-story office in the New York branch of Wolfram & Hart, "I wasn't expecting to meet again so soon. Is everything alright?"

William Bracken stood on the other side of the office, browsing a wooden bookshelf that spanned the entire height of the wall. In particular, he paid attention to a series of unmarked books, each sporting a maroon leather spine. The Senator cocked his head to the side with a shake of his head.

"In a manner of speaking," Bracken said. "Facing resistance in securing that file, though."

Lilah sat up a little straighter with a furrowed brow. "Any way we can assist?"

"Actually, that's not why I'm here," the Senator mused, closing the distance between himself and Lilah's ornate desk before lowering himself into one of the overly comfortable black leather chairs. He sank into the cushions with a sigh. "I'm hoping you could provide me with some information."

Lilah frowned and set her pen down. What could Bracken be after? Trying to hide the confusion twitching over her brows, Lilah nodded and waved her hand, motioning for Bracken to continue.

"Richard Wilkins," Bracken said.

Lilah's frown deepened. "The former mayor of Sunnydale, California?"

"Among other things," Bracken countered with a knowing smile.

One of Bracken's more unsavory contacts in the world had told the Senator about the former mayor of the small California town decades ago. How Wilkins had founded Sunnydale, right atop a Hellmouth, and over the decades he cultivated evil until the tiny speck of Southern California land was a haven for beasts and demons.

Until the Slayer came along.

Still, Wilkins' ultimate endgame – Ascension – continued unabated. He took every step necessary in order to accomplish his goal. He even succeeded, Ascending while delivering the commencement speak at the local high school.

Success was brief, though; the Slayer had enlisted the help of the graduating class – along with several other outsiders – and Mayor Wilkins was vanquished when an explosion destroyed the high school.

Bracken, who still had his eyes on the White House, wanted to know why Wilkins had failed. He refused to believe it was because of some superpowered cheerleader and a bunch of riled-up teenagers.

"I can have that information for you tomorrow," Lilah said, choosing not to press her latent curiosity. Knowing Senator Bracken the way she did, she knew he would reveal his gameplan in due time.

If there was one thing her time with Wolfram & Hart had taught Lilah, it was patience.

"Excellent." Bracken stood to exit the office, stopping at the doorway before turning to regard Lilah again. "Oh, and one more thing…tell Lindsey that P.I. he referred me to? Every bit the pain in the ass he said."

A knowing smile crept onto Lilah's face. "You have no idea, Senator."