Author's Note: Since I'm bad at summaries - basically, the Apocalypse is going to happen, the characters I listed earlier have to stop it, there will be a lot of angst and possibly some romance, and a surprise OC. That's about all I have. You'll just have to read it to find out more.

Since this site doesn't allow more than two fandoms per crossover, I'll say it right now - this isn't just a Buffy The Vampire Slayer/Psych crossover. It's a Buffy The Vampire Slayer/Psych/Supernatural/Sherlock/The Inside crossover. Yeah, talk about insane.

Anyway, this is rated T only because, well... end times. There might be some violence involved. Actually, there will undoubtedly be violence. Possibly a little bit of cursing. I can promise that there will be no sexual content beyond possible kissing either. I don't write NSFW stories. If that's what you're looking for, you should probably go elsewhere.

That's about it! Just bear in mind that this is my first hopefully-novel-length fanfiction ever, and the first fanfiction beyond a one-shot that I've written in many years. So please be kind!

vVvVvVvVv

"No!" Lassiter placed a stack of case files on his desk. "For the last time, Spencer - it's over a five hour drive from here to Sunnydale, and I don't care whether Gus's car is in the shop. I am not spending five hours with you in my Crown Vic."

"Aw, c'mon, Lassie. What's bothering you?" Shawn sidled up beside him and hopped up to sit on the desk. "You're more snippy than usual. Did someone spit in your coffee? Spill guacamole on your tie? Steal your wittle teddy bear?"

Lassiter shoved Shawn sharply enough to send him slipping off the desk and clambering to catch himself before he crashed to the floor. Unfortunately, he took the entire stack of case files and a notebook with him.

Rolling his eyes, Lassiter muttered in frustration and knelt down, yanking the case files out of Shawn's hands and slapping them down on the desk again. Before he could make a threat or push Shawn out of the room, Juliet and Gus returned, followed by Chief Vick.

Lassiter immediately stepped away from Shawn and stood ramrod straight. "Chief."

She cast a short glance at Shawn - who was still sprawled out on the floor - before raising an eyebrow at Lassiter. "Detective."

Gus hauled Shawn to his feet. "C'mon, Shawn. Pay attention. The chief is gonna brief us on our new case."

"'Our'?" Lassiter repeated. blinking. He stared at the chief. "They're not coming too, are they?"

"Detective, based on our knowledge of the current situation, they might be able to help," Chief Vick pointed out, her voice grudging.

"What is the current situation which we will be able to help with?" Shawn asked, brushing his shirt off and then leaning against Lassiter's desk again. "A drug ring? Serial killer? Is your house haunted by ghosts that keep knocking over your pineapples? We're happy to help. Pineapple tipping is a heinous crime."

Ignoring his guesses, the chief continued. "There have been reports of highly strange activities in Sunnydale, and extreme acts of violence. Worse than anything we've seen here in a long while. I'm sending a team over to investigate; in this case, that team comprises of yourselves, Detective Lassiter, and Detective O'Hara."

"I have just one question," Juliet said. "Sunnydale is far from our territory, so to speak; why are we being sent all the way out there?"

"Because I've been ensured that it is highly urgent by an acquaintance who lives there," Chief Vick responded. "They have heard of the SBPD's success with a variety of cases, and asked if I would send someone to Sunnydale to help; they asked for the best people my department had."

"And so you called us in." Shawn leaned back, a smug expression on his face.

Chief Vick fixed him with a stony stare. "No, Mr. Spencer, the 'best people my department had' is Detective Lassiter and Detective O'Hara. I'm sending you because my acquaintance told me that a psychic detective might be useful to them." She handed a folder full of papers to Lassiter. "This is the information they sent regarding recent happenings in Sunnydale. Leave as soon as possible."

vVvVvVvVv

"Hey, Mel." Special Agent Danny Love beckoned to the agent who had just entered the room. "C'mere. We have a new case."

The woman - Special Agent Melody Sim - sauntered over to Danny's desk, tucking a few locks of red hair behind her ear. "Good. Don't get me wrong, that vacation was great; but after three days of total peace, I could go for some action. What is it this time?"

"Sudden outbreak of crimes in Sunnydale," Danny replied. Before he could continue, Mel cut him off.

"Okay, what's the catch? We both know Web doesn't just send his team out for random crimes. What is it about this case that caught his eye?" Mel casually reached across the desk and took Danny's coffee mug, lifting it to her lips.

"Dunno. He gave me this case file, and that's it. It doesn't say much; it sounds weird, but doesn't seem weird enough to make Web jump on it." Danny stretched out his arm and took his coffee back before she had the chance to take much more than a small sip. She quirked one eyebrow at him, and he arched both of his back at her in response.

"Odd." She picked up the case file and skimmed through it. "Sunnydale, huh? That's not far from here; a few hours' worth of driving, I'd guess. A lot of weird stories have been in the papers about that place, I guess… that might be part of it…"

"Yeah," Danny said. He watched her look over the information.

"Are Paul and Rebecca coming with us?" Mel asked, continuing to look through the papers in the case file.

"Nah. It's just us. He has Ryan and Locke on a different case."

"That's even weirder. It isn't like that whole 'separate the team and make them work against each other' thing he does; that would mean we're on opposite sides of the same case. We never work apart except for that." Mel's brow furrowed briefly. "Now I really wonder what this whole thing is about."

"Mm." Danny took a swig of his coffee, wiping his mouth on the back of his hand. "Well, we'll find out soon enough. We can stop by your place so you can pack-"

"I actually haven't unpacked from my vacation, so." She scoffed in wry amusement.

"Yeah, well, we're leaving on business. So just in case you have a bunch of leisurely items in your suitcase, we'll stop by your place before we hit the road anyway," Danny retorted, shooting her a sardonic little smile. "We leave tonight."

vVvVvVvVv

A black Impala sat parked outside of a grocery store, somewhere in downtown Seattle. Behind the wheel, Dean Winchester was 'resting his eyes'.

In reality, after nearly twenty minutes of waiting for Sam to return with the food, he had begun to get sleepy. It had been a peaceful week - even two days without being chased or attacked was a luxury, and it had now been six days. So he felt a little more at ease.

He was awakened mere minutes later by his towering, long-limbed brother climbing back into the car. "Sorry. There was a line at the register, and then Bobby called." He blinked. "Were you sleeping?"

Dean stared, then sat up straighter. "No. What did Bobby want?"

Sam absently chewed on a stalk of celery he had procured from one of the bags in the backseat. "He says there's a problem down in Sunnydale. Y'know. California."

"There's always a problem down there," Dean retorted. He twisted around to reach into the backseat.. "You remembered to get those barbeque potato chips, right?"

"Yeah, they're in there somewhere." Sam continued his explanation. "No, he said that there's rumours of something real big that'll be happening down there soon, and that we should be there."

"What kind of big?" Dean asked. He spotted the chips and snatched them out of the bag. "'Crazy poltergeist' big? 'Rampaging witch' big? 'Vampire infestation' big? Because I'm pretty sure Sunnydale has the handling of vampire infestations down pat."

"No." Sam turned with a more serious expression than he had worn before. "Something crazier. And bigger."

vVvVvVvVv

Rain pelted down on London, a cold and whispering cascade that hadn't let up in nearly a week. DI Greg Lestrade was grateful that he had been able to stay inside at work; there hadn't been much cause for him to go out on arrests or drug busts. Crime had reached a slow spell, it seemed - much to his suspicion.

Sipping from a mug of tea he had made in the break room, Lestrade returned to his desk and sat down, placing the tea off to the side. An envelope caught his eye and he picked it up to read it. He frowned, then looked up. "Who put this here?"

Sally Donovan poked her head around the corner. "I did. Apparently it's urgent; urgent enough that the postman brought it here rather than leave it back at your flat."

"Huh…" Lestrade carefully opened the envelope and withdrew a letter, which he then read. A spark of confusion set off a flicker of fear.

Sally, no doubt noticing the distant expression of concern on her boss' face, made her way back. Anderson followed on her heels. "What is it?"

Lestrade blinked, lowering the letter and looking up at them. "It's, uh… from a friend of mine. Well, an old friend of mine; I've not seen him in ages. At least twenty years. I didn't even know he had moved to North America; we haven't really even been in contact."

"Is he dead?" Anderson queried, earning himself a pointed glare from Sally.

"No, no." Lestrade set the paper down. "He needs my help with a case of sorts."

"In America?" Sally exclaimed. "You can't just leave and fly halfway across the world."

"I have no choice," Lestrade responded. "Trust me, I need to go. Scotland Yard can manage without me for a short while."

"What's going on?" Sally pressed. "Next to nothing can cause you to be so flippant about your work."

"Then that ought to be proof enough that this is urgent," Lestrade responded, fixing her with a level stare that showed he meant what he said. "I'll finish up the paperwork and what-not for today, and be on the first plane to California tomorrow morning."

vVvVvVvVv

Giles leaned back in his chair, breathing a quiet, tired sigh and taking a sip of tea. Just as he shut his eyes, the noise of several teenagers throwing the door open and ambling inside jarred him back into an open-eyed state.

"Hey, G-Man." Xander trotted over and plunked himself down in one of the chairs.

"I asked you to please stop calling me that," Giles said wearily. He glanced up at Buffy. "Well? Any activity?"

"Besides a few more vampires than usual, nothing." Buffy sat down on the edge of his desk. "Are you sure that this whole blood moon thing is going to be a problem?"

Xander raised both eyebrows. "He just sent out multiple 'urgent messages' to who knows where. I'm pretty sure he thinks it's a problem."

"It aligns with everything in the texts about the End Times," Giles replied, taking his glasses off and rubbing the bridge of his nose. "As this is the Hellmouth, we should plan for the worst. I've contacted a few different people - some are well-versed in supernatural matters, and the others will all be very useful in other ways."

"You mean they're the kind of people who think vampires are just figures from Dracula films," Buffy said.

"Well… sort of, yes. And we may have to explain things to them. But please trust me when I say that they will be of help to us at this time. And we do need help; this isn't something we can take upon ourselves alone." Giles looked at Buffy, Willow, and Xander in turn. "If what is coming is truly the Apocalypse, we will need allies. I believe that those who should be arriving soon will be those allies."