Something about Dean's rough treatment of the unknown creature made Sam uncomfortable. True, it was a monster that they suspected of potentially murdering children, but the way it looked at his brother with big, shiny eyes filled with a kind of fearful naivety made Sam sure that it was nothing more than a child itself.

As Dean slammed the turtle-creature against the wall again, Sam noticed a faint snarl coming from his left. He started to say his brother's name, but was interrupted by a large mass slamming into him at the same time as the dim, flickering red light from the discarded flare went out completely. He heard Dean curse explosively, and the sounds of struggling. Suddenly fearful that his older brother was in trouble, Sam attempted to buck off the heavy weight pinning him against the slimy brickwork of the tunnel, only to stop rigid as a cold metal point pressed meaningfully into his throat. His unknown assailant spun him around, keeping the sharp weapon poised, and restrained the hunter with his other arm.

The arm around his chest felt…distinctly non-human to Sam. While the creature was warm-blooded, his skin seemed to be covered in smooth scales. Sam's analytical brain puzzled over the contrast, until he was thrown back into the present situation by a sudden flare of light as Dean switched on the Maglite strapped to his belt. The increased visibility allowed Sam to recognise that Dean was definitely spooked. He restrained the captive creature in a hold mirroring the one currently restricting Sam's movements, the shotgun in his hand trembling slightly at he kept it jammed under the creature's jaw. The reason for his big brother's distress was obvious; Dean's eyes were fixed on Sam and his current predicament, and was obviously wary of pushing the newcomers into a rash action.

Three more, Sam thought to himself, for the flashlight had revealed that the turtle-monster holding him had certainly not come alone. How did they survive down here all this time?! It was hard to see much in the dim light, but the monsters seemed to be wearing…protective pads? And bandanas? The metal prong pressing uncomfortably against his carotid artery was certainly proof of the fact that they were carrying weapons.

Then, to the hunters' vast surprise, the monster wearing a blue bandana spoke, the voice distinctly male, and pissed. The swords in his hands were held in a steady, unwavering grip, aimed at Dean's throat.

"Get your filthy hands off of my little brother."

Momentarily frozen in shock by the confirmation that the creatures were intelligent, Dean was unable to produce the sharp wit he was famous for. Nonetheless, Sam's brother tightened his grip (the captive turtle squeaked, and the others tensed noticeably), and rallied a little.

"Tell that thing to get HIS filthy hands off of MY little brother!"

Weak and all as Dean's comeback was, Sam caught the look his brother flashed to him, and, with the little leverage that was available to him, slammed his elbow back into his captor's chest. The blow bounced harmlessly off of the monster's carapace. The pressure on his neck increased.

"Keep still," a furious voice snarled slightly below Sam's ear, "and maybe I won't give you an extra hole to breathe through."

His brother's eyes were incandescent with fury, and he jammed the shotgun even harder against his captive's jaw. "Try it, and we'll see how long your little bro can survive without a face."

This in turn inspired the sword-wielding turtle to narrow his eyes dangerously. "You think you can pull the trigger before I take off your head?"

Honestly, if he hadn't been in a potential life-or-death situation, Sam would've rolled his eyes at all the smack talk. Apparently, someone shared his opinion.

"Okay, stop," the turtle in the purple bandana groaned, stepping forward into the light. "Look, we mean you no harm, so everyone, just put down your weapons so I can take a look at Mikey."

The…turtle in the purple bandana seemed to be the voice of reason within the group, Dean guessed. The one pointing freakin' swords at his neck flicked his creepy white gaze to the speaker, and, after having a silent conversation, capitulated, reluctantly stepping back and lowering his weapons. After expressing his disbelief at the surrender of his two pals, the turtle holding Sam released him with a snort of disdain. Sam lowered his arms in a non-threatening manner, and stepped to the side. Clearly his little brother had forgotten that they were dealing with potential child-killers. Although…the signs they had picked up back at the hospital pointed more to a classic haunting than giant turtle-monsters. Still, better safe now than dead later.

The smallest turtle seemed to be getting heavier in Dean's hold, but he put a pin in that for now, and addressed the purple guy.

"I'm not just gonna 'put down my weapon', buddy. For all I know, your brothers are gonna take our heads off as soon as I let him," he gestured with his chin at his captive, "go. No dice."

Purple blinked, the white in his eyes retracting to reveal cinnamon-brown irises. He held up a pair of large, three-fingered hands in a placating gesture.

"Listen. My little brother, the turtle you're holding? Something is making him very, very sick, and we have no idea what it is. We think it might have something to do with whatever is killing those teenagers, and we'd like to help you stop it."

Ignoring the incredulous sounds that Red and Blue were making, Dean stared the tall turtle out. The fact that he had voluntarily revealed potentially incriminating information made their story a little more plausible. He seemed utterly sincere, and his eyes kept flickering to the turtle Dean was holding. The hunter raised an eyebrow, and looked down too. He knew nothing about the physiology of these creatures (honestly, the whole 'mutants in the sewers' deal was too cliché for words), but he had to agree that the little guy wasn't looking good. He seemed to be getting heavier by the second, his breath coming in little rasping pants. Beads of sweat stood out on his forehead, and his skin was icy cold. Making a snap decision, Dean motioned to his brother.

"Sam, get over here."

Sam approached slowly, hands still facing outwards, and crouched in front of Dean and his captive, intelligent eyes taking in the deathly pallor and violent shuddering of the turtle in orange. He glanced up at Dean, his gaze solemn. "Same symptoms, dude. I don't think they're the ones doing this."

Dean had pretty much reached the same conclusion. No-one was this good at acting concerned about a family member, and the creatures obviously wouldn't infect one of their own. The little guy looked pretty far along, too.

As if to cement his findings, the turtle suddenly sagged in his grip. Thankful that Sam was there to take some of the weight, he lowered the turtle to the sewer floor, discarding his shotgun in the process.

"Easy, easy…" he found himself murmuring. Dean could feel the anxious desire to rush forward emanating from the other turtles, and realised that the shotgun was still within easy reach. Strangely reluctant to keep them from their ailing brother, he sent the gun skittering into a dark corner with a firm kick, mentally apologising to his father for the ill treatment of a precious weapon. Immediately, the three turtles raced to their brother's side, surrounding him protectively. Sam moved back to a respectful distance, and Dean moved to follow him, but found his arm clamped in a death grip by the semi-conscious creature.

"Let go, buddy, c'mon," he encouraged, gently tugging at his sleeve caught in the trembling green fingers. It did no good; the turtle curled closer to him with a quiet groan, the hard plate on his chest heaving.

The other creatures were staring at him.

"What's he doing?" Sam ventured from behind him.

Purple grinned ruefully, displaying a gap in his front teeth. "You're warm; warmer than we are," he said to Dean. "He's been doing that to us for days. 'Course, we didn't notice much of a difference at first."

"He's cuddly," supplied Blue.

"The word you're looking for is 'clingy'," scoffed Red.

Dean shared a quick glance with his little brother, who raised his eyebrows back. These guys, unusual as they were, were clearly a family. They displayed the same concern, love, and fond exasperation that he felt for his own little brother. That, more than anything, convinced him that they weren't behind the murders.

He looked for a long time at their fussing over the youngest, wondering whether, and if so, how, to apologise.

"…You guys have names?" he settled on.

Red glowered at him, Purple spared him a glance from where he was mother-henning Orange, but Blue met his gaze for a few moments. Dean got the distinct impression he was being sized up.

"…Leonardo," Blue said. "This is Raphael," he gestured to the glaring turtle in red. "…Donatello, and…and Michelangelo."

Blue – Leonardo – gestured to the smallest turtle in Dean's arms, his voice sad. Behind him, Dean could hear Sam exclaiming "You guys are named after Renaissance masters?!" but his entire focus was on Michelangelo. He placed his warm hand on the turtle's cheek. When comparing him to his bigger brothers, it was obvious that there was something seriously wrong. The freckled skin was cold, freezing cold, and felt dry and slightly rough. Michelangelo's breaths came in shallow pants, making a whistling sound when Dean pressed his ear against the cool, smooth armour against his front. Dean was no doctor, certainly, but he did have a certain amount of knowledge about the progression of ghost sicknesses. He looked to Donatello, who was currently trying to rouse his brother.

"Hey…Donatello? Can you just get me a look at his eyes?"

Donatello smiled a little, once more revealing the gap in his teeth. That small imperfection made him seem all the more human. "It's Donnie, and sure. Mikey?" he called softly to his little brother.

A groan was his only answer. He huffed with poorly feigned impatience.

"Come on, Mikey. Open your eyes. Uh…"

He looked inquisitively at the hunter beside him.

"Dean," Dean supplied. "That's Sammy."

"It's Sam," came the indignant mutter from behind them.

Donnie nodded. "Nice to meet you. Mikey, Dean wants to get a look at your eyes. Please open them for us?"

With what looked like a great effort, the little turtle prised one eyelid open. Dean had a split-second to realise that the eye was covered in a milky film like the kids in hospital before Mikey emitted a startled squeak and latched on to his brother. To be fair, Dean admitted ruefully to himself, the last thing the turtle had seen from him was a shotgun ready to blow his head off.

The older turtle pulled his little brother into his arms. "Ssh, it's okay, they're friends, Mikey," he said. "Don't be scared, we're all here."

'Friends' was a strong statement, considering that they had all been trying to kill each other not ten minutes ago. Still, Dean thought, it was pretty nice to be trusted this soon after averting a major tragedy. He was alarmed when Mikey convulsed suddenly, but soon relaxed when he realised the orange banded turtle was laughing.

"Some…friends…y-you guys…have," Michelangelo wheezed. "A-am I about to…get my head mounted on a w-wall…or what?"

Sam knelt beside them once again. "We're sorry about before," he said softly. "We're trying to find out what's making you and the kids in the hospital sick. How are you feeling now?"

Thank god for Sammy and his touchy-feely nature, thought Dean. The little guy looked calmer already, relaxing further into his brother's hold.

"L-little better. W-who…?"

"We're hunters. We wanna stop the thing that's making you feel bad. Dean, have you got the EMF?"

Ignoring the little guy's murmur of "Are you s-sure we aren't gonna get stuffed and put in a freakshow?" Dean nodded and grabbed his improvised EMF from his duffel. The older turtles' eyes immediately flicked to the device as he positioned it over their prone brother.

"Woah," growled the aggressive Raphael. "What the hell is that, and what is it doing near Mikey?"

Keen to diffuse the mounting situation, Sam stepped in to explain. "It's an EMF; it measures electromagnetic fields that spike when something supernatural is nearby. Dean made it himself," he added with a hint of pride. "It's totally safe. We just want to check whether there's anything attaching itself to Michelangelo."

Busy rolling his eyes at Sam's praise, Dean almost didn't notice the little tug on his sleeve. He looked down into milky blue eyes.

"Will it hurt?" Mikey whispered. His freckled face was set into an expression Dean remembered from Sammy's earlier years; the scrunched nose and fearful eyes not wanting to let on how scared the youngster actually was. He felt his face settle into the gentle calm that had always soothed his own little brother.

"It's not gonna hurt, buddy. I promise." He said decisively. "See?"

Dean turned the improvised machine on, and, ignoring its customary bleeps, ran it over his own arm. The noise from the EMF remained steady.

"Didn't hurt a bit," he grinned, his smile growing wider when the ailing turtle beamed back at him. The elder turtles, sensing their little brother relax, dropped their aggressive stances and crouched once more beside him. Leonardo gave Dean a fractional nod that he took as a sign to continue. Moving the prongs closer to the little turtle's middle, his heart sank as the EMF emitted a piercing squeal and the dial flickered into the danger zone.

The green-eyed hunter exchanged a look with his little brother. The emotions in Sam's eyes echoed his own; fierce triumph at getting one step closer to solving the mystery warred with the pity they both felt for the little family gathered around them.

There wasn't much time.

Raph glanced quickly from one human to the other. While he didn't trust any humans other than April and Murakami-san, these two jerkwads were the best hope they had at finding a cure for Mikey.

However, the looks on their faces weren't particularly reassuring.

"What? What's wrong?" he demanded, hands twitching anxiously towards his sai. If they'd hurt Mikey with that dumb contraption…

The taller one – Sam, his mind supplied – jolted slightly as he was startled out of his freaky staring match with his brother. Credit where credit was due, he managed to meet Raph's eyes squarely.

"That noise tells us that something supernatural has definitely wrapped itself around Michelangelo," Sam said firmly. "I'm not sure what it is yet, but we'll find out."

Sneering at the downcast faces his brothers were directing at their youngest, Raphael snatched up his sai with a snarl.

"Screw this," he snarled. "If there's something stuck to Mikey, I'll just cut it off!"

Spinning his weapon, he carefully scrutinised his little brother, and was about to swipe when four varying pitches screeched "NO!"

Loudly.

With accompanying grabby-hands.

With his hands pinned behind his back, he couldn't deal out any serious retribution, so Raph settled for glaring at his two older brothers. Thankfully, the humans had been too sensible to attempt to hold him back. "What?!"

Donnie's dark eyes were squint with the reprimand he so desperately wanted to give.

"You can't just 'cut it off', Raphael, it's a ghost. Which means it's incorporeal. Which means you were about to risk seriously injuring Mikey!"

Gruff with embarrassment, the red-banded turtle shook his brothers off. "Well excuse me, mister paranormal expert! Weren't you the one that didn't believe in all this crap an hour ago?"

"Even I can't ignore evidence backed up with solid scientific proof, you cretin."

"Scientific proof!? This guy waves around an old Gameboy and suddenly he's the answer to all our problems!?"

"Guys…"

"Quiet, Leo! Okay Raph, if you've got any better ideas, let's hear 'em! Because I don't know what's wrong with Mikey, and I sure as hell don't know how to fix it. So instead of sitting there, making the problem worse, maybe you should stop whining and shut the hell up!"

Utterly taken aback by Donatello's outburst, it took Raph a few moments to come up with a good retort. Thankfully, Dean decided to interject.

"Walkman."

The three healthy turtles looked at him like he'd lost it. The elder human rolled his green eyes and elaborated.

"I made it from a Walkman, not a Gameboy. And if you three are about done with your hissy-fit, you might wanna take a look at your bro. He's not doin' so good."

Three heads immediately whipped around to focus on their youngest. Mikey lay propped against Sam's knees, and was seemingly struggling for breath; each shaky exhale was followed with a strangled whistle from deep in his chest.

"Mikey! God, I'm sorry!" Raph cried, instantly grabbing for his little brother's hand and gripping it tight. Donnie snatched up the other and held the limp hand to his own forehead.

Leo squeezed his eyes shut against the sight, then steeled himself to look up at Dean.

"What do we need to do?"