Your crossover: L&O meets Highlander and Buffy the Vampire Slayer.

Hidden Things
By The Sentinel

Spike entered the bar, his long, black trench coat only a little out of place. His old, worn, Doc Martens better suited to a dive bar, not this place. No matter. He made his way to the bar and patted his duster and jeans pockets, making sure he had cash before ordering a beer from the bespectacled man pouring drinks.
He took a sip of the amber alcohol and turned his head to the voice that addressed him. "I beg your pardon?" he asked, forcing his British accent a little.
"Tell me... How are you able to dye your hair if you don't have a reflection?"
That's funny, I don't recall mentioning my lack of reflection to anyone in this place. Spike shook his head and took another sip from the mug in his hand. "Is that question hypothetical, or have you been listening to rumors?"
"Oh, so you mean you're not a vampire?" the intrusive man asked with an eyebrow twitch.
"No. And even if I was, how would you know?" Spike returned with a snarl.
The man sipped his own beer, smiled, and nodded toward the entrance. "Same way I know he's a lawyer."
Spike turned to the man in question; salt and pepper hair slightly windblown, tall, lanky, dressed in a dark suit and tie. "Yeah? So, who is he?"
The man shrugged. "Don't know. Can only tell you he's a lawyer."
"Hmm. So, who are you?"
"Name's Adam Pierson. You?"
"Spike," he replied, sipping his beer again.
"Spike. Hmm, I used to have a pet called..."
"Don't even go there, mate," Spike said, eyes narrowing and Adam responded with a grin.
Both Adam and Spike glanced at the tall man who approached the bar and ordered a Scotch. Spike turned back to Adam. "Lawyer, eh?"
Adam nodded.
"Wanna play a little game?" Spike asked with a sly grin.
Adam shrugged.
Spike quirked an eyebrow and began a tale, strictly for the supposed lawyer's benefit. "So, you see, bitch stole my car, drove to L.A. and had an affair with this ex-friend of mine." Spike took a sideways glance to see if the lawyer was listening. "All of this after she tried to beat me to death. Still healing from that one."
"Tough woman," Adam commented.
"Still don't have m'car back. I liked that car." He looked at the lawyer again. The lawyer did not seem particularly interested in the conversation. Right then. I'll make you get interested. "So, what do you think, mate?" Spike asked the lawyer beside him.
"That you should find another car," he responded plainly.
Spike frowned. "What's with you? Job getting you down?"
"You could say that." He sipped his Scotch.
"Yeah? What do you do?"
"I, sir," he waved his glass toward Spike, "am a Manhattan DA." He sipped his drink again. "And I am extremely stressed out and would like nothing more than to take a vacation."
"That didn't sound too convincing, mate." Spike drank his beer.
"No? Eh, probably not. The closest I take to a vacation is prosecuting a case in Brooklyn."
Spike took a moment to glance at Adam, then turned back to the lawyer. "I'm Spike."
"Interesting name. I take it you don't work on Wall Street."
Spike frowned again. "Oh yeah, mate, this just happens to be casual Friday. What do you think?"
"Probably best. Name's Jack." He toasted Spike again with his Scotch.
"So, what do you people do for fun in this town?" Spike asked and leaned his back against the bar, watched the crowd.
Jack laughed. "I'm probably not the best person to ask. I don't tend to get out much." He signaled the bartender to refill his glass.
"Right then. Name your pleasure: darts or billiards."
Adam leaned in toward Spike's ear. "You might not want to give him the choice."
"Why?" Spike snarled.
"He's got a good game," Adam responded and hitched a thumb at the dartboard.
Spike turned hard to face Adam. "How do you know this stuff?"
Adam shrugged. "Too many years of people-watching."
"What are you, mate, a bloody stalker?"
Adam shrugged, a half smirk on his lips.
Spike turned back to his commiserating friend.
"Darts." Jack swallowed the last gulp of his second Scotch and rose from the barstool.

I told you not to let him choose," Adam said to Spike as they exited the bar with Jack.
"Yeah, yeah." Spike brushed a hand over his bleached hair. "Guess we should find something that I'm good at."
"Spike we can't do that," Adam stated. Then leaned close to Spike's ear. "He puts people away for what you're good at."
"I didn't mean that. There are other things I can do. Or we could find something you're good at."
Adam laughed. "No. Research is not for everyone."
"You want a job? If you're good at research, we could use you," Jack offered, hands in his pockets as he stared across the street.
"Maybe," was Adam's response.
"We could use Spike too, but since he can't go outside during the day..."
Spike turned to the lawyer, his face a study in shock and fear. "What?"
"You mean, you're not a vampire?"
"I'm sorry? Does my shirt say Property of Count Dracula or something? What do you know about vampires?"
"This is New York, mate," Jack mocked Spike. "We've seen everything here."
"Right then. So what kind of work did you say you wanted me for? Because I don't do so well with legal stuff."
Jack smiled. "Yeah. I know. The two-seven picked up your car three nights ago."
Spike sighed. "So that's where it went." He waved a hand. "Keep it. Maybe that bitch will stop trying to track me."
"So there actually is a woman? I thought you'd made that up," Jack said, still staring across the street.
Spike was aghast. "Was there a bulletin sent out on me? Or am I really that transparent?"
Adam laughed; Jack joined him.
"This isn't funny," Spike fumed.
"Really it is;" Adam began, "did you think Sunnydale was the only town that had ever seen vampires?"
"Of course not. And that doesn't explain how you would know that I am a vampire."
"No. I'm a researcher for an organization that tracks immortals," Adam said.
"Right. And as I'm not of the mortal persuasion, I qualify?"
"Not quite. These immortals aren't 'undead.' They're alive, human, just live longer than most. We knew you'd been around for a while and a few members of our organization had seen you enter some fatal situations and live to tell about them. So, we kept an eye on you. Of course, then we found out about your blood habit and amended our records and left you alone."
"Nice to know you care so much."
"Actually, the organization was a little scared. Afraid you might be some immortal that had been around for a long time and we hadn't been keeping records on you, and it would have been a big thing. Bad."
"Yeah, fine. I'm not on the alert list anymore. And good for me that you were scared. Means I was doing my job." Spike shifted into his vampire face - raised browridge and elongated canines - and turned to Jack, asked Adam, "So, what about him?"
"Him? He's just a lawyer."
"That's it? A lawyer who's great at darts? Hrmph."
Jack frowned. "Would you like me to have you arrested and carted off to Rikers? I'm sure they'll have a grand time trying to figure out why they're one inmate short come sunrise."
Spike rolled his shoulders back and held his head high. "I believe I was just threatened by an officer of the court."
"You want to know what else I'm good at?" Jack inquired.
"Wait, I know this one," Spike closed his eyes and pressed his fist against his forehead. After a moment, he lowered his hand and opened his eyes. "Motorcycles."
He received a pair of astonished gazes from Jack and Adam.
"What? You didn't think I couldn't play this game, did you? Jack, the District Attorney - Executive Assistant District Attorney - rides a motorcycle. And Adam Pierson, whose name is not really Adam Pierson, is an immortal, not a researcher. Okay, so he has been a researcher, it's not necessarily his trade."
"And this conversation is getting a bit weird," Adam commented.
Jack frowned. "Yes, how exactly do we each have all of these details?"
"Well, I was actually going to ask if anyone knew how I'd gotten to New York." Spike rolled his shoulders and resettled his duster.
"Where exactly is Sunnydale?" Adam asked, ignoring Spike's question.
Spike wrinkled his nose and twitched his lip. "It's in California. Not far from L.A."
Jack made a sigh of displeasure at the mention of Los Angeles. "I won't be going there."
"I'd recommend against it," a feminine voice spoke from a nearby streetlight.
"Blo-ody hell," Spike drawled.
"Hello, Spike. Nice to see you making new friends. Too bad you won't be able to spend any more time with them."
Confused, Jack asked, "Who is she?"
"Oh, the little blond girl who's threatening to take me away from my new found friends? That's the bitch. Buffy," Spike replied with a snarl.
"Uh huh," Buffy said, "and I'm going to kick your ass all the way back to Sunnydale."
"I don't think so," Adam stated as he stepped forward.
"No?" Buffy queried, arms crossed over her chest.
Jack shook his head. "No. And if you try, I'll have a warrant issued for your arrest. This is my town. Means, my rules."
"You do know what he is, right?" Buffy threw her arms outward to emphasize her point. "Of course you do. My friend cast that little spell for you. So, you know pretty much everything about each other. And you still don't want me to take him away?" she asked, pointing at Spike.
"No. We don't. He was a little annoying at first..." Jack began.
"Hey!" Spike was a bit hurt.
"...but, he kind of grows on you. We had a nice game of darts and a chat about various things. Beer being a major topic. No different from any other... actually, quite different from other nights at the bar."
"Really? And why's that? He start a fight? Try to eat someone? Because it's always fun to watch him do that then get zapped by that government implant..."
"No," Adam jumped in where Jack had left off. "It was fun. Enjoyable."
"You had fun with Spike?" Buffy asked, skeptical.
Adam and Jack nodded.
"See, Slayer, if you'd stop trying to kill me, you might learn some of these things," Spike informed, his head held high.
"I don't want to know 'these things,' Spike. I want you dust."
"How sweet. I've got a better idea. Why don't you run along back to Sunnydale and I'll stay here in New York, never to bother you again?"
Adam and Jack shared a look that said they were not too sure of this plan.
"Sorry, Spike. No go. Back to Sunnydale." Buffy pointed to the west.
Spike's eyebrows rose. "Why don't you start and I'll follow. Not sure I like New York much anyway. Smells like Angel was here."
"Spike, how would you even know that?"
"Look, Slayer, I'm going back to Sunny-D. Though I have no idea why. It's just going to take a little while, so go on ahead without me and I'll catch up."
"Fine." She turned and walked away.
"Bitch," Spike muttered.
"Are you going back?" Adam asked expectantly.
"Yeah. Just takin' the scenic route."
Jack and Adam watched Spike walk down the street, his long, black trench coat swaying behind him.
"Think he'll make it to Sunnydale?" Jack asked.
"He will if I have anything to do with it. Even as a vampire, he still has potential use to my organization. Actually," Adam began as he gazed in the direction Spike had gone, "so are you, Jack."
"How's that?" he asked, a bit confused.
"You never wondered why you weren't killed in that accident several years ago?"
Jack was astonished. "How did you know about that? No one knows about that."
"Magic spells don't work on immortals. Vampires yes, immortals no. You researched vampires and knew about Spike before he came to town. Probably because you got word from Buffy or her friends that he was coming. Am I right so far?"
"Amazingly accurate for someone I just met."
"So, you walked into that bar knowing Spike would be there."
"Sure. How do you know all of this?"
"I've been watching you since that accident."
Angry now, Jack snapped, "Why?"
"Remember I said magic spells don't work on immortals?" Adam waited for Jack's acknowledgement. "You're immortal, Jack."
"That's insane."
"When's the last time it took you half the day to get over a hangover? Or, you had a cold? Or a migraine?"
"When I walked into that bar tonight. Got a headache like you wouldn't believe."
"Disappeared quick though, didn't it?"
"Yeah. How...?"
"You sensed me. I embellished it a bit, but that was me."
"You are crazy."
"Maybe, but like you, I'm also immortal. And now, your teacher."
"You've got a lot to learn."

whaddya think?