Dean hated a lot of things. He couldn't stand salad, slow drivers pissed him off, and it drove him crazy when Sam would drum his fingers on the dashboard of the impala. But one thing that Dean hated more than anything these things combined was the annoying, egotistical detective known as Sherlock Holmes.

Sherlock was rude. He would spout off personal, irrelevant deductions at the most inconvenient times, he didn't say thank you, or please, or any of the other magic words they taught in kindergarten. He walked into Sam and Dean's motel room like he owned the place, and proceeded to insult their living conditions. He was an insufferable know-it-all and continued to correct Dean's grammar after he threatened to pistol whip him at least eight times. Basically, he was Dean's worst nightmare.

Even Sam had a hard time finding something good to say about Sherlock. Of course, he was very good at his job. He was a hard worker, and he truly did see things that others did not. But Sam found it hard to focus on his good points when Sherlock woke them up at two in the morning to borrow their father's journal. Twice.

Sherlock's companion, though, was a pretty pleasant guy. John swore like a sailor, which won Dean over, and his affinity for literature had Sam practically swooning. He was polite, and kind, and he always apologized for Sherlock when he insulted someone. If anything, John Watson was Sherlock's only redeeming quality in the Winchester's eyes.

Their hatred towards the British detective could have had something to do with the fact that he was practically holding them hostage as well. If Dean complained about having to cart Sherlock around, he would flash his phone, which had the real FBI on speed dial. Number three, to be exact.

Even so, the Winchesters had to admit that it was nice to have the help. Since Bobby's death, they hadn't had much in the way of backup.

"So," Dean began one cold, early morning. "Where are we off to today?"

He eyed Sherlock from his rearview mirror, waiting for that smug smile to spread across his lips. Instead, the detective gave him a cold, hard expression.

"A crime scene. There has been another killing."

Usually Sherlock would be excited at the prospect of having a scene to inspect, but the body count that the killer had been racking up kept his attitude in check. In the week that he had been in America, six people had already passed away due to mysterious chest wounds, and he didn't have so much as one suspect.

"Jesus, what does that make? Five?" Dean asked.

"Six, actually," Sam answered grimly. Their failure to capture and kill whatever was doing this was weighing heavily on his shoulders as well.

"Six people dead, and we don't even know for sure what's doing this. Are we losing our touch or something, Sammy?"

"I would certainly hope not," Sherlock interrupted. "I won't hesitate to revoke our previous arrangement if you prove to be useless."

Dean shot Sherlock a look through the rearview mirror again, willing his gaze to burn the arrogant detective.

"Yeah, so you've reminded us. Every. Single. Day."

"Dean," Sam warned.

"It's okay," John intervened, his voice apologetic. "Honestly, we know you two have been doing your very best. It seems that this is a strange case for involved."

Dean's smart remark caught in his throat at John's kindness. He had to remember how his harshness affected not only Sherlock, but his blogger as well. The detective may have been obnoxious and rude beyond belief, but John was a good man that happened to be caught up in Sherlock's whirlwind of deductions, and Dean couldn't harm one without damaging his relationship with the other.

"I think we're all a little tired and frustrated," Sam agreed.

Dean rolled his eyes, but followed the directions that Sherlock gave him from that point after. He didn't argue with Sherlock about the route they took to the scene, though it was longer than the one that he had in mind, and he didn't shout at him for slamming the impala's door. That latter had taken quite a bit of self-control.

"Back again, agents?" the sheriff inquired when the boys stepped onto the scene. Dean tried to smile politely, but it turned to a grimace.

"Yes sir. What can you tell us this time?" Sam asked before Dean could put his foot in his mouth.

"Same as the others. Fatal chest wound, dumped in a secluded area, no other obvious clues or injuries. I don't know what to tell you boys. This killer isn't giving me much to work with."

"Nor us. But we're working on it. Mind if we take a look at the body?" Dean asked.

"At this point, I don't really care what you do, agent Tyler. I just want this killer caught."

Sam placed a reassuring hand on the sheriff's shoulder as he passed, the other three trailing behind him. He stooped down to get a closer look and Dean copied his movements. When they came up empty, they moved to give Sherlock room to investigate. The detective set to work as soon as they were no longer in his way.

"I can tell you one thing for certain," Sherlock said as he scanned the victims clothing with his magnifying glass.

"What's that?" John asked.

"This killing is most certainly not like the others."

"What d'ya mean?" Dean asked, leaning in to watch Sherlock work.

"It seems that our killer is getting careless. See this?" Sherlock motioned to the victim's stomach. Dean shook his head, seeing nothing out of the ordinary. "They've left behind a piece of hair."

Sherlock pulled out a pair of tweezers and picked up the hair gingerly. He examined it under his magnifying glass before continuing.

"The victim's hair was a very light red color, while this one is silver. Given where the body was found," Sherlock explained, gesturing to the back alley that they were located in. "I am willing to bet that not many people come here, and the person who reported the body certainly didn't have hair this color."

Sam nodded along with Sherlock's explanation, while Dean stood with his arms across his chest.

"And look at the shine to this hair. It seems almost… unnatural, doesn't it? I'm nearly certain that, when examined under a microscope, it will prove not to be human."

"Well, that blows the lid off of our guess," Dean huffed, annoyed. "Werewolves are human. Sort of."

"What about a shifter? Remember that dude that could turn into a dog? The little gang that he was a part of? Maybe there was more of them. And maybe some of them could turn into wolves," Sam suggested.

"That doesn't explain the way these people died, though. If they just wanted them dead, there are easier ways to do it than busting their ribcage open. They needed the hearts for something."

To this, Sam shrugged his broad shoulders.

"Wait… So, you're saying that not only are there werewolves, but there's other people who can turn into animals?" John asked, his eyebrows raised in shock. "What else is out there? Are you going to tell me that vampires are real next?"

This was a response that the Winchesters got often. When something finally happened to shatter a person's false sense of security, they had all kinds of questions. They always wanted to know what myths were real, which ones weren't, and how they could be killed. A few had even asked if Santa Claus actually delivered presents to all the good little boys and girls around the world. Unfortunately, as far as the Winchesters were aware, good old Saint Nick was one of the few untrue rumors.

"Well…" Dean began. "If you mean the classic, Dracula vampire, no. But bloodsuckers sure are out there."

"Jesus!" John exclaimed breathlessly.

"I'd stop asking questions now, if I were you," Sam cautioned. "I've had people run away screaming."

John opened and closed his mouth a few times, like he wanted to respond, but settled on staying quiet. He ran a hand through his short, blond hair to give himself something to do. The fair locks stuck up in random places and Dean had to stifle a laugh at the sight.

"If the killer is in fact a 'shifter' as you call it, then how do we track it down?" Sherlock asked.

"That's the tough part. They don't leave a trail like other supernatural beings do. They don't even have a signature way of killing. Spirits set off EMF readers, werewolves take the heart, and vamps drain the victims of blood. But shifters… they can kill in all kinds of ways. And depending on what they can shift into, they can disappear from the scene without a trace. I think the only chance was have of stopping this thing is by catching it in the act," Dean replied.

"How are we supposed to do that? It already has all of its victims. For all we know, it's hiding them in the sewers and killing them off whenever it gets the itching to," John said.

"Well, that's something we're gonna have to figure out," Sam said.

"Please tell me this doesn't mean another day in the library," Dean whined.

Something in Sam's expression told Dean that that was exactly what it meant.

"Found anything?" Sam asked in a hopeful voice. Dean shook his head tiredly.

"We've been here for five hours, and I'm coming up with jack. There's no local legend about shifters, no headlines about killings like these. It's starting to look like we're not going to be able to solve this one," Dean said.

"You give up too easily, Mr. Winchester," Sherlock stated as he dropped a book in front of Dean. "It would seem that there is in fact a legend that fits our current predicament."

"Well, come on! Spit it out! We don't got all day!" Dean exclaimed.

"We do not have all day," Sherlock corrected. "That aside, though, I do believe that I have discovered what we are dealing with. It's called a shadow walker."

"A shadow walker?" John inquired, setting down a large pile of books on the table. "What have I missed?"

"Nothing yet, John. A shadow walker, my young hunters, is precisely what it sounds like. It is a creature that lives in the shadows that materializes during the full moon. They are known for kidnapping young men and women in sinful relationships."

"Sinful in what way?" Dean asked.

"In any way. Any young person who has sex before marriage, cheats on their significant other, or engages in a homosexual relationship is in danger of being abducted by a shadow walker."

"Okay, but that doesn't explain the animal hair or the missing hearts," Dean said.

"If you waited for me to finish, you would realize that it does." Sherlock shot the elder Winchester a deadly look. "When shadow walkers materialize, they do so as wolves. They hold their prey hostage for several months, torturing them in various ways, before finally ripping their hearts out."

"Kind of poetic justice, if you think about it," Sam said. "I mean, they're killed by the very organ that represents love."

"Precisely!" Sherlock praised. "At least someone around here understands."

Both John and Dean scowled at this.

"Okay, Mr. Know-It-All. If you're so smart, how do we kill this thing?" Dean sneered.

"Just like any other shape shifter, Dean. With silver."