A/N: This one could be read as a continuation of The Nature of the Wolf, but it doesn't have to be. It's quite a bit shorter than that one, but I'll still be updating a chapter a day.

Chapter 1

The house at the end of the lane was a decrepit Victorian, imposing in its stateliness. The wide porch groaned as Sam and Dean Winchester shifted forwards, shotguns and books held at the ready. The ghost that had been haunting this address had been sporadically attacking people for the last hundred years, and the list of victims had no clear pattern. Dean's heavy breathing and the long creak of the elaborate stained-glass front door were the only noises in the heavy silence of the autumn air. Sam shivered as they cautiously crossed the entrance hall, eyes darting across the dusty room. There was something about abandoned houses that always creeped him out. They were almost ghosts themselves, decaying memories of a happier time.

The echoing silence of a country night magnified all the sounds around them, from the shuffle of Dean's boots to the rustle of the pages Sam turned through, trying to find more information on the Charlevoix ghost. Dean's hand suddenly raised, his head cocked like a bloodhound on a scent. Their eyes met in the moonlit room. There was a noise coming from the basement, a murmur and a clatter that hadn't been there a moment ago. With a grim nod, the two hunters opened the door leading down. Neither of them noticed the flickering figure in the shadows, watching them.

The half-rotted stairs creaked gently in the still night as the Winchester brothers edged down them, eyes and ears open for disturbances. Sam's eyes widened as they reached the bottom and the sounds they had heard from the entry hall became clearer. There was no way anyone could mistake what that rhythmic fleshy slapping noise was, nor the low groans and soft whimpering. There was no mistaking Dean's lascivious grin, either.

He leaned closer and spoke in a satisfied whisper, "Well, Sammy, looks like we should investigate."

Sam tightened his lips in exasperation. "Dean, no. You just want to take a peek."

"Sam, we have a responsibility. Those people could be in danger." His wide-eyed attempt at an honest expression was about a believable as a used car salesman's.

"Dean, they are in danger. This isn't a peep show."

"Of course not!" He paused. "Still, we should get a lay of the lay first—land. I meant land."

Sam pinched the bridge of his nose, his eyes shut tight. "Dean, are you sure you aren't fifteen anymore? Because sometimes, I wonder."

By the time he opened his eyes, his brother had edged carefully around the corner of the shelves and was staring at the source of that deep, shuddering moan.

Sam's eyebrows drew together. He knew his brother far too well, and Dean's leer had been seared in his brain ever since he had decided to hit on "Little Sammy's" eighth grade prom date. It had been the first time a girl had ever liked Sam back, and his older brother had come swaggering in, full of bad pick-up lines and misplaced confidence. Carrie had refused to speak to Sam again for the rest of the two months he was at that school. She'd avoided even looking at him. So yeah, Sam knew what Dean's perving face was. That perplexed expression was not the look of Dean Winchester, Casanova Extraordinaire. That was Dean Winchester, Officially Confused.

Peering around Dean's shoulder, Sam blinked. The glow that had been visible through the dusty shelving wasn't from an ancient-but-still-serviceable light bulb. There was a tall blue box standing in the corner of the basement, and the light was coming from the windows under the "Police Public Call Box" sign that wrapped around the top. The dim light also illuminated the couple that had been the source of the noises earlier—a tall, skinny man that was resting his head in the crook of a blonde girl's neck as she lay collapsed on the high counter. They were half-dressed and still breathless, with a confused mixture of a brown suit on both of them. The girl giggled, and the man made an inquisitive noise into her neck.

"Aren't we s'posed to be investigating a space-time anomaly?" Her voice was light, with a strong British accent.

The man raised his head and pursed his lips, mock-glaring at the girl. "Rose Tyler, I didn't hear you complaining a few minutes ago. No, what I heard then was more along the lines of Yes and Harder and Oh God Doctor." He paused and grinned smugly. "Thanks for that, by the way. Not every day that I get deified."

The girl—Rose, apparently—snorted and smacked his shoulder lightly. "Oh please, you get deified every second Tuesday."

He made a pleased-sounding hum into the curve of her neck. "Really? I had no idea it was so regular."

She giggled. "Something like that, anyway." She prodded his ribs, as his chest was still draped over hers. "Shove off."

"Why should I? You're so lovely and warm. You, Rose, are like my own personal space heater. It's marvelous."

"You say the most romantic things, Doctor."

"I do, don't I?" He ignored her half-hearted prodding and cuddled closer, and Dean stepped around the corner.

"What the hell do you two think you're doing?" At his question, the Doctor shot upwards and Rose yelped and yanked him back to her, using his chest to cover hers.

She glared at Dean from behind the Doctor's cotton-covered shoulder, hastily pulling her bra back up and her shirt down. "I could ask you the same! What, bored an' decided to rub one off? Beat it, mate!"

Dean's indignant protest was rather tellingly high-pitched, and he cleared his throat before continuing. "Of course not! This place is dangerous—it's definitely not the spot for some late-night nookie."

Sam stepped around the corner once he'd checked to make sure they were decent, the Doctor hastily yanking up his brown pinstriped trousers and tucking in his dark blue button-up. Rose straightened what seemed to be the matching jacket around her once she'd pulled down her denim skirt. "My brother's right. This place is dangerous—there's been a ghost haunting this area for the last hundred years, and forty-seven people have died. It's no joke. You need to get out of here, as soon as possible."

The Doctor turned around, and his expression was as serious as Sam's. "We know. We came here because of that 'haunting'—and really, how unimaginative can you get? Honestly. Everything's a ghost. Here a ghost, there a ghost. It's rather repetitive, don't you think?" Sam blinked. The man's mood had shifted like quicksilver from solemn to petulant.

Rose redid her hair in a loose bun and sighed. "Off track again, Doctor."

"Am I? Oh, yes. I suppose I am. Still, it's a good point."

Dean stepped closer, his posture smug. "If it's not a haunting, what is it?"

"It's an empathetic projection of the final moments of a human-extraterrestrial mental symbiosis."

Rose frowned. "Wait, how is that not a haunting?"

The Doctor turned wide eyes to Rose, "You understood that?"

"Always with the tone of surprise." She grinned at his wince. "'Course I understood it, you lump. I was one of the top agents at Torchwood, after all."

"Yes. Right." He coughed lightly, looking sheepish. "Sorry."

Sam cleared his throat. "You said extraterrestrial." The Doctor nodded. "So, aliens."

"One alien in particular, actually. Judging from the strength and longevity of the projection and the circumstances of the Cartwright family's deaths, I'd say the daughter had bonded with a renegade Psukhikian." At Rose's indrawn breath, he nodded grimly. "Exactly."

Dean frowned. "Wait, what's a Puss-hickey whatever?"

"Psukhikian. The Psukhikians are some of the strongest telepaths I've ever encountered, but they tend to keep to themselves—they're mental symbiotes, you see, and they don't know how to communicate with non-telepaths all that well."

Dean frowned. "If they keep to themselves, how come one ended up here?"

"There was a war on Psukhikos oh, about 500 years ago, your time. Started over something completely trivial—I think it was something about fruit prices—and ended up nearly devastating the planet. There were several Psukhikians who decided that maybe the rest of the universe wasn't so bad, after all, and they've ended up scattered through the planets."

Dean frowned and scratched his ear. "If it was 500 years ago, though, how come this one only showed up a century ago?"

The Doctor glanced at him as he stuck his hands in his pockets, rolling forward onto the balls of his feet. "Well, I did say that they keep to themselves. Without impetus, why would they have sophisticated interstellar travel? Whoever this one was, it probably only arrived just before it melded with Lucy."

Sam's jaw dropped. "You mean it lived through 400 years of travel?"

"Oh, yes. In fact, I'd hazard a guess that that might be the reason it connected with Lucy as it did—for a telepath, being cut off from all others of your kind is excruciatingly painful." Rose reached out and took the Doctor's hand, and he smiled softly down at her.

"So that's what it did? Just latched onto whoever was nearby?"

The Doctor looked thoughtful. "I doubt it. Psukhikians have to have a certain affinity to communicate, you see. Lucy most likely had latent telepathic abilities—but because they hadn't manifested, she didn't know how to handle the connection."

Rose nodded grimly. "The reason Psukhikians tend to stay away from others is their empathetic abilities. They're not just telepaths, you see. They feel everything their counterpart feels—it's why the war got so bad. All the anger and fear that comes with war? Imagine that runnin' through your head constantly, times a million. It wasn't until enough of 'em left that things started to calm down. A lonely Psukhikian, though, they're desperate for connection. They'll try to attach themselves to the minds around them, but a telepathic bond like that is an extraordinarily intimate thing—" she caught a smoldering glance from the Doctor and flushed bright red— "and the other minds often reject the symbiote. Goin' through that, after already being cut off from the rest…" she grimaced. "The results aren't pretty." She gestured at the sheaf of papers Sam held. "You're prob'ly got a record of 'em right there."

Dean frowned at them. "The local police just said that Lucy Cartwright had gone insane and murdered her family. You're saying that the real culprit was a crazy alien?"

The Doctor cocked his head to the side and stared off in thought. "Well, it was most likely a combination of both. Did you happen to find any mental profiles of Lucy Cartwright, interviews conducted by the police with people who knew her and her family? Small town like this, this incident had to have made waves."

Sam nodded. "According to investigations after the fact, the Cartwright family wasn't a happy one. Joseph Cartwright, her father, was allegedly a holy terror of a disciplinarian—the local doctor visited the Cartwright place almost monthly to deal with bruises and breaks. Lucy's little sister, Alma, died under 'mysterious circumstances' the year before the murders. Her mother, Marie, was an invalid who was confined to her room and refused to speak to—or of—her children."

Rose's breath hissed through her teeth. "Why would she do that?"

"Apparently, she had always been sickly after being pregnant with Lucy, and it was Alma's birth that confined her to permanent bed rest. According to members of the community who knew the family, Joseph never forgave her for not giving him a son, and he took that frustration out on his daughters."

"And then the Psukhikian joined with Lucy, and the symbiote had to deal with both of their loneliness and pain. No wonder it went mad." Rose's eyes glittered with tears in the dim light, and the Doctor wrapped an arm around her shoulders comfortingly.

"Yeah, and then it killed the entire family and forty-seven other people over the years." Dean snorted. "It's a sob story, sure, but that doesn't make that many deaths just disappear."

"Dean."

"What? It's true, Sam. Yeah, it went nuts, but we've got to stop it." He turned back to look at the Doctor and Rose, who were watching him warily. "How do we get rid of it?"

The Doctor rolled his eyes. "It's never as simple as just 'getting rid of it'. Something that's been here for a hundred years, that's powerful enough to kill multiple times, you've got to be careful around it. No amateur exorcism is going to work. "

Dean's jaw dropped. "Amateur! Sam! This limey bastard just called us amateurs!"

Sam ignored him and set his gun on the counter. "What would you suggest, then?"

The Doctor's eyebrow raised, and Sam had to tamp down the feeling that he'd just passed some sort of test. "If the symbiote's still here and still killing, then it was never able to separate itself from Lucy. It's a vicious cycle—her pain increased its pain, which increased her pain, etc. By now, it's probably nothing more than a feral mind, lashing out against anything that hurts it."

Dean nodded, "Okay, so we've got to break 'em up."

The Doctor's eyes widened. "It's not that simple." His gaze darted around the dim basement, and he began pulling Rose back towards the police box. "You'd better hope that it wasn't around to hear you, just then."

Dean snorted, but he edged closer to Sam. "Only sounds we heard earlier were from the two of you."

The Doctor's hand was on the door when the air around them stilled, all outside noise vanishing. The Doctor cursed in a musical, chiming language and slipped his key in the latch, but he was too late—a powerful surge of anger tore through all of their minds, sending their bodies slumping to the dirty floor.