A/N: First crossover I've ever published, but this idea popped into my head this afternoon, and I had to write it. My Lucifer/Chloe is a bit rusty, but hopefully not terrible; I'm a little more confident on my Sam/Ruby 1.0, but there's not as much Ruby sarcasm as I'd really prefer. Oh well.

A/N 2: Other than being the Katie Cassidy version of Ruby (Genevieve/Ruby 2.0 was a completely different character that simply had the same name, IMO), and all the wonderful S3 sarcastic wisecracks from her having definitely been said, this story doesn't follow any Supernatural timeline or Ruby plot line, or occur at any particular point in it; similarly, no specific point in the Lucifer timeline either. Just a fun little clash between two supernatural fandoms, where Ruby truly is good (or trying to be), and really does like Sam because he's tall; and she loves a tall man (and fries — deep-fried crack, and all).

As Chloe pulled her car up to the crime scene, she saw two figures that were not her own standing next to what she assumed was the body of the murder victim. The man was dressed in the typical stuffy suit of a Fed, while his partner, a blonde female, was in a red leather jacket and tight-fitting jeans; not standard dress for any department she knew of.

Exiting the car, she walked across the grass towards them, briefly being aware that her partner, Lucifer, had wandered off in a different direction — but she was too interested in who was stealing her case to worry about him at the moment.

"Excuse me," she said as politely as she could as she walked up. "Who are you?"

"Hi, I'm Agent Evans, and that's Agent Johansson, FBI," replied Sam, holding out his badge.

Ruby, who was kneeling next to the body, carefully examining the neck, completely ignored the petty human.

"Detective Decker," replied Chloe with a nod. "What's the FBI's interest in this case?"

But before Sam could reply, they heard a very surprised sounding voice echoing from across the lawn.

"Ruby?"

Ruby, who'd just stood up, froze, before spinning around, unable to believe she was actually hearing that voice.

"Lucifer!?" she exclaimed, unable to stop the words from escaping her lips.

Despite her shock, she could sense Sam's hand going for the Colt at her words; and it pulled her out of her shock sufficiently enough to simultaneously throw out one arm to signal Sam not to pull the Colt out, and to move her other hand to the handle of her own concealed knife.

"I didn't know you were up here!" continued Lucifer jovially, as he strode across the lawn to where they Sam, Ruby, and Chloe were gathered at the body. "Of course, I haven't had much contact with anyone from hell since I left. How have you been?"

Ruby slowly let go of her knife that she'd been fingering under her shirt, resulting in Sam releasing his grip on the Colt as well.

"Hello, Lucifer," she replied warily.

"Oh, don't worry about me," said Lucifer, sensing his former underling's hesitation and wariness of him. "I don't care that you're out of hell. I left that world completely behind when I left there. But who's your partner? I don't recognize him from our world, above or below."

"Please ignore my partner's devil and hell nonsense," interrupted Chloe, stage whispering loudly to Sam and Ruby. "He really is helpful at solving crimes, I promise."

"Sam Winchester," replied Ruby, completely ignoring the human, looking slightly more relaxed than she had been when she'd first seen Lucifer was there, but still alert.

"As in the infamous half-demon Winchester hunter?" Lucifer asked with excitement. "So good to finally meet you!" he continued, holding out his hand for Sam to shake, which the hunter cautiously did. "Everyone knows the Winchesters, of course, and I've heard a lot about you and the other children, although I'd honestly forgotten all about the whole the demon children thing since I moved up here. So what's a hunter and a demon doing at our crime scene?"

"We think this is a vampire we've been tracking's latest victim," replied Ruby, before Sam could try going back to their FBI cover stories; no way Lucifer would believe she was actually an FBI agent, and trying to deceive the Lord of hell usually wasn't the wisest move. Plus, he already knew all about their world, being a very major player in it. "And now that you know what we're doing here, what's the Lord of hell doing at a crime scene in Los Angeles?"

"Ooh, vampire, cool," responded Lucifer, looking quite excited at the prospect. "As for what I'm doing here, as I'm sure you heard, I decided to take a break from hell about five years ago, and came here to LA. And then not too long ago I got involved in solving a police case with this lovely young lady, and realized that I quite liked working with the police; you know, punishment kind of being my thing, and all."

"Satan, the Lord of hell, helping humanity; who would have ever seen that coming," smirked Ruby. "But as noble as that is, this is our case now. So if you'll tell your pesky little human to take all her cops away, Sam and I will get to work on finding the vampire who did this."

"Okay, that's enough! I don't have a clue who you guys are, but you're not taking over my case," exclaimed Chloe, fed up. She had a murder to investigate, and that wasn't going to happen if she couldn't rid of these two crazies who apparently believed Lucifer's nonsense. "And based on how well you apparently know Lucifer, I'm beginning to doubt you're even real FBI agents. In fact, I've half a mind to arrest you right now. But this is my jurisdiction, and until I hear directly from Washington, you're not barging in and taking my case."

Sam sighed, knowing there was no way they were going to get this woman to drop the case, and knowing she'd probably arrest them if she caught them investigating it on their own. So looking over at Lucifer, he asked, "Would you be willing to share this case with us? Since even if you did somehow find the vampire who's doing this, we both know she'd be in way over her pay grade, and forgive me if I don't trust the devil to kill a dark creature."

"Of course!" exclaimed Lucifer excitedly. "This is going to be so much fun. And obviously, no offense taken; I'm actually rather surprised you haven't already tried to send me back to hell."

"I would have if Ruby hadn't told me not to," replied Sam bluntly. "And I still might if you give me reason to."

"Fair enough," replied Lucifer, before turning to Chloe. "So, Detective. Two more consultants on this case. Exciting, isn't it?"

Chloe merely rolled her eyes as she sighed deeply before moving over to the body, not bothering to deign any of what was going on with an answer. She knew that no matter what answer she gave, there was no way she was going to get rid of Winchester and Ruby, just as she hadn't been able to get rid of Lucifer the first time they'd met. And given Ruby's apparent friendship with Lucifer, the blonde probably knew some of the same tricks Lucifer did that'd prevent her from being able to successfully arrest the blonde if she wanted to. So best to let them tag along with Lucifer for the time being, and hopefully solve the case before they screwed everything up.

"So! The Devil and Ruby on a hunt with a Winchester! This'll be fun!" said Lucifer to Sam and Ruby as he took the Detective's silence to mean she wasn't objecting to the plan.

"Please. We have never done anything together before," retorted Ruby. "And I won't even hesitate to kill you if you so much as look wrong at Sam wrong. Got it?"

"Wouldn't expect any less of a demon," replied Lucifer with a smile.

"Now that you've decided my job for me, can we actually get to work on the crime scene?" came Chloe's slightly irritated voice, reminding them all that they actually had a job to do.

A job that, though she didn't know it yet, was going to severely test her belief that the devil, demons, vampires, and the rest of the supernatural wasn't real.