The Scooby-Doo Theory

Summary: Castle and Beckett work on another strange case. Naturally, Castle thinks there's a murderous sewer monster, and Beckett tries to find the real killer. But this time, there might not be a logical explanation. Threeshot

"Wow. What kind of animal can do this?"

Stunned, Kate stood next to their most recent vic, Castle at her side. As she stared down at the scratched, bitten, and bloody corpse, she could only guess what animal might be the culprit. A wolf, maybe?

The body had been found in Battery Park by a passing jogger at about five in the morning, and they'd arrived on the scene minutes later. Kate had a large cup of coffee in her hand, courtesy of Castle. But after seeing the mauled body, she realized she was wide awake. She gave the cup to him to hold as she crouched down next to Lanie so she could get a better look at the marks, careful not to disturb the scene.

Lanie sighed. "Don't know for sure, but the vic bled to death within a half hour of the attack, about three hours ago. Thanks to the blood trail, we can tell our poor vic crawled over from that open manhole." She pointed to one a couple feet to their left, unnecessary since crime scene tape surrounded it. "Which is impressive, given how deep some of these scars go. This man was a fighter."

"You'd have to be to get away from a mutant wolf," Castle suggested, his head tilted as he stared down at the middle-aged, Caucasian male body. He was so lost in thought that even Kate could tell he was already thinking of story plots for his next book. "Yeah, definitely going with mutant wolf. Or some other large mammal."

With a roll of her eyes, Kate retorted, "It's not Wolverine, Castle. Maybe an animal escaped from a zoo."

"If it was, it'd have to have been a reptile," Lanie said. She held up a pair of tweezers, which were gripping a small piece of lizard skin.

Kate groaned. Lizard skin, open manhole cover… She looked at Castle expectantly.

"What?" Castle asked, his face innocent. He quickly added, "By the way, that X-Men reference was totally hot."

Kate rolled her eyes again, but otherwise didn't acknowledge the comment. "Look, I know you, Castle." At least if she got all the crazy speculation over with right then, she wouldn't have to listen to any of it later. "Where's your wild theory about sewer alligators? Out with it."

Disappointed, Castle frowned. "I'm really that predictable?"

"Since you were talking about mutant wolves two minutes ago, I have to side with Beckett on this one," Lanie put in. Smug Kate nodded in agreement.

"But you just said it was a reptile!" Castle began, the embarrassing exchange already dismissed. "So it is possible! What reasons could there be for a scratched up body and reptile skin?"

There aren't many, Kate thought. Still, she only needed about thirty seconds to think of one. "Maybe…someone really wanted this guy dead, so he or she bought an animal to get the job done." She paused. "We should get records from stores or individual sellers that carry large reptiles. Fortunately, I don't think many people have giant lizards as pets."

"In this city, you never know," Castle reminded her.

"That's true. There's all kinds of freaks out there," Lanie remarked with a chuckle. She then became business-like again. "Anyway, we think the crime happened wherever that manhole cover leads to, but you'll need to wait a little while. CSI is still looking for another way in."

Though the complication would frustrate her, Kate wasn't too upset. She, Ryan and Esposito would have plenty of pet store records to keep them busy. "Thanks, Lanie. I'll check in later."

Another weird case. Rick loved it.

As he sat in Beckett's office, he held a notebook in his lap, ready for the burst of inspiration he knew was coming. Already, ideas for the next Nikki Heat book were swirling around in his mind. Nikki Heat versus the mutant sewer lizard… he thought happily while he wrote the idea down. Wait, wait…Nikki Heat versus the alien sewer lizard…better… Maybe if he didn't like how this case turned out, he'd give the next book a slight sci-fi twist. Fans wouldn't mind if he kept everyone in character, right?

Overwhelmed by the possibilities, he nearly jumped when Beckett slammed the phone back on its base. Fortunately, she was too distracted to notice his mock-able response, so he said, "No luck yet? You've been calling places for hours."

"I'm aware of that, Castle," Beckett snapped. At his raised eyebrow, she sighed. "I'm sorry, just more than a little aggravated right now. No pet store or seller we've called so far even carries a lizard as big as the one Lanie says attacked our vic. Actually, she said the lizard that did it would've had to have been…" She paused, then reluctantly finished, "Human-sized."

Like she undoubtedly expected, Rick's eyes widened. "So it really is an alien sewer monster?" he exclaimed. She gave him an exasperated glance. In defense, he held up his notebook. "Sorry, brainstorming."

"In the real world, Castle, we think of the next logical explanation," she retorted. "I'm thinking our killer made this look like animal attack to throw off suspicion. All of those scratches could've easily been made by a human being using some sort of weapon."

"But what about the bite marks? And the lizard skin?" Rick asked hopefully.

Beckett shrugged. "Easily explainable too. Maybe the attacker did use a real animal as part of his or her cover. It's pretty smart, actually. When this leaks to the press, we'll start getting crank calls about sewer alligators more than actual leads."

"Like Scooby-Doo villains," Rick reasoned. At her confusion, he said, "Oh come on, don't tell me you've never watched Scooby-Doo. It's a classic!"

"I've seen Scooby-Doo before. I just don't think it relates to our case," Beckett replied.

With a sigh, Castle patiently continued, "Scooby-Doo villains, famously known for dressing up in costumes. Locals always think they're terrorized by a ghost, witch, mummy, what have you. That way they always steer clear of wherever the villain is hiding out. Of course, until the fearless mystery gang investigates, and discovers it's just regular bad guys wearing masks."

He was genuinely surprised when Beckett actually paused in consideration. "Huh," she remarked. "That would explain the picture."

"Picture? There's a picture and you didn't tell me?" Rick exclaimed, a little hurt.

But she ignored him as she went to her office door. "Ryan, Esposito? Either of you have the picture of our suspect?"

"Got it right here, Beckett," Ryan said as he approached her with the glossy, magnified photo in hand.

Beckett took the picture and held it up to the light so all three could see it more clearly. It showed a long, slimy tail, about six feet in length as far as they could tell, turning a corner in the dark sewage pipe. The tail was probably even longer though since they couldn't see any of the body to which it was attached.

"Wow. Now that is creepy," Rick remarked. He had to give credit to the CSI team member who took the picture. If he'd seen that, whatever camera he'd been holding would've been dropped as he ran for the nearest street ladder.

Ryan nodded. "Gave me shivers when I first saw the picture. Can't imagine seeing it in real life."

As she stared at the picture with a critical eye, Beckett asked, "Now, that could easily be man-made, right? Sure, it looks realistic, but anything's possible with all the new materials out there these days."

"I can't believe you didn't tell me about this," Rick retorted childishly.

With a sigh, Beckett explained, "Sorry Castle, but I'd heard enough crazy ideas for one day, and with all the calls I had to make, I didn't feel like hearing more." Before he could protest further, she said, "So what do you think? We should do a check on all possibly synthetic materials that could be made to look like this tail, and the green slime too. Then we'll see who's been buying large amounts of it lately."

"Sounds like a plan. I'm on it," Ryan said as he took the picture back and went to update Esposito with the latest development.

Once Ryan was gone, Rick considered what he'd just learned. "Beckett, here's a question," he began while they went back into her office. "When whoever took that picture saw the tail, did he or she go after it? Of course, this is under the presumption that the person didn't faint. Or run screaming for his life."

"From what I understand, the photographer did run after it," Beckett replied. "But when he rounded the corner, it seemed that the suspect was gone." At his raised eyebrow, she added, "It was dark. The suspect was moving fast and the CSI couldn't see far enough." She sighed when she looked down at the number of pet stores she still had to call. "You know Castle, between pet stores and the new theory, I'm going to be making calls for a long time…"

Rick nodded. "And you want me out of your hair, got it. Let me know if you find anything." To be honest, he would've left soon even if she hadn't told him to go home. Inspiration wouldn't wait all day.

When he did get back to his place, Rick eagerly turned on his laptop. But instead of writing, he did some outlining first. Between last week's "alien"/secret agent encounter and this, he already had some great material. Which was good, because he'd been worried about writer's block after how long it took him to write the last novel.

Of course, he'd have to severely tweak the agent encounter so he didn't break confidentiality. But fortunately he had some buffer since the book would be fiction. Who would ever take him seriously, even if he did recount the adventure word for word?

He was so lost in his writing that he didn't even look up when Alexis got home from school. His mother was auditioning from some off-Broadway role she was pretty excited about, but after writing for hours, he was lucky if he could remember her birthday, never mind the play's title. Still, he was curteous enough to greet his daughter before she went upstairs to do homework. "Hey honey, don't mind me, I'm in the zone!"

Alexis laughed, then kissed him on the cheek in greeting before she went into the kitchen to grab a snack. "Interesting day at work, I guess?"

"Oh yeah. Looks like Manhattan has its very own Loch Ness Monster," Rick said, adding dramatic flair to his voice.

"Really, Dad?" Alexis replied, an eyebrow raised. "Last week it was aliens, now this?"

Rick frowned. "Okay, so it's not really a Loch Ness Monster. But that would just be so much cooler, wouldn't it?" When she nodded in agreement, he continued, "CSI grabbed a picture of a slimy tail rounding a corner when they were investigating a sewer. Beckett thinks it's just a guy in a costume though."

"You mean like Scooby-Doo?" Alexis asked.

"That's my girl! See, you made the connection!" Rick exclaimed. "Anyway, yes, like Scooby-Doo. Personally I think Beckett's just unwilling to accept that there could be an alien lizard running around under Manhattan."

Alexis shook her head. "Can't imagine why." A bowl of cereal serving as an easy snack in hand, she sat down on the couch across from her father. "Dad, quick question. While working with Beckett, you've run into a lot of stuff that seems paranormal or sci-fi at first, then you find out the truth when the investigation is over. But…do you actually believe in that stuff? Or is it just your writer imagination going overboard?"

The unexpected inquiry made Rick stop typing. "Well, that's not really a quick question…" he muttered, already wondering what his feelings on the subject were. Whenever he started rattling off crazy theories, it was done in a joking manner, mostly to get on Beckett's nerves. He usually never stopped to think if he really believed in whatever idea he was spouting at the moment.

"Well, Alexis…I don't know, honestly," he began, which made his daughter's eyes widen in surprise. "I guess…I guess I'm just open-minded to the possibilities. I'd like to believe that magical and other-worldly stuff is out there. But am I as naïve as I appear to be, talking aliens and mutant wolves at the first sign of something strange? Of course not. That's just to annoy Beckett."

That got Alexis laughing. "I'm not surprised. But…mutant wolves?"

"Yeah, at first when we saw the vic, I thought he might've been attacked by a mutant wolf," Rick explained. "Then Lanie showed us the reptile skin. Now I've moved on to mutant and/or alien lizard."

Alexis shook her head in disbelief. "Sometimes your cases are so interesting that you don't even need to embellish them for your books."

"Yup. And thank goodness for that," Rick said as he happily went back to outlining.

A couple of Author's Notes:

- This is my first attempt at a multi-chapter Castle story. And writing an investigation. So I apologize if there are any mistakes character-wise, or concerning police procedure.

- I originally wanted to write a Castle crossover with Wizards of Waverly Place, since they're my two favorite shows, and they both take place in Manhattan. But the more I thought about it, the more it became just a Castle story. So, there will be some WOWP, but very little, in one short scene in the last chapter.