A/N: This is a multi-chaptered fic that I'm planning on working on along with some others I have going. As such, I'm aiming to update about once a week. I didn't mean to write this but I'm just so damn impatient for season eight, and I haven't found many Purgatory fics, so I just had to! Set immediately following the final scene in 'Survival of the Fittest'.There won't be any Sam, at least in the earlier chapters, as it focuses on Dean and Castiel in Purgatory. Title gratuitously stolen from an episode of The X-Files of the same name. Hope you enjoy it :) Please drop me a comment with your thoughts because I love love LOVE reviews!

The shadowy figures lurk between the jagged trees, growing disturbingly close to the lone stranger in their midst. Dean spins around wildly, eyes frantically scanning the dark shapes for any sign of Castiel. He calls for him again in hushed tones and pulls his knife out of his back pocket, knowing full well that it will be a useless defense against the things that stalk him in the darkness. Though his body is poised for a fight, the knowledge means that his mind threatens to shut down in its rapid hurtle towards full-blown panic. This cannot be happening, Dean thinks desperately. It has to be some kind of nightmare, like the ones he became so acquainted with following his time in Hell. One of the shadows advances towards him with a low susurrus of a growl that is almost enough to send a shiver down his spine. And then he sees the creature responsible for the terrible noise. Standing as tall as the blackened trees surrounding it, it is unfathomably mammoth, almost but not quite blending into the solid wall of black around it.

Its inhuman, terrifying, unlike anything he's ever seen before, and in that instant Dean is sure that this is the end. But suddenly Castiel is in front of him, face tense with fear, bright eyes boring into Dean's, hand reaching for his forehead in a blessedly familiar gesture. Then they are somewhere else altogether, somewhere almost as dark but with distinctly fewer growls, Dean notes with relief as he takes a quick scan of his new surroundings. Castiel is at his side but quickly moves away, patrolling the parameter of the cave and murmuring under his breath in a language Dean doesn't regognise. Dean's eyes scan the area as he struggles to catch his breath, knife still drawn, searching meticulously for any sign of a threat. Finally, he finds his voice again.

"What the hell was that thing?" he asks, his breathless voice giving away more than he wants it to.

Castiel turns away from the task at hand, meeting Dean's gaze.

"It doesn't have a name," he explains in his low growl. "It is just one of the many manifestations of tortured souls in purgatory."

Dean lets out a nervous laugh and stares at the ground for a moment.

"Well that's just fantastic isn't it?" he says so quietly that it's almost to himself.

Castiel goes back to his pacing and whispered words, and Dean looks up and watches him closely for a few moments.

"What are you doing?"

"Ancient Enochian protection spell. I'm not sure how effective it will be here, but it's better than nothing," Castiel explains without looking up, and Dean nods his approval before going back to his own assessment of their makeshift fortress. They appear to be in some kind of wide mouthed rocky cave and though it feels significantly safer than his previous surroundings, Dean doesn't like the look of the shadowy trees beyond the entrance.

"You know, for a minute I thought you'd left me out there," he admits in a strained voice, still slightly out of breath.

Castiel stops his search and turns to face the hunter, as though he'd forgotten here was there until he spoke.

"I would never do that," he replies sincerely, fixing Dean with an intense blue stare.

Unspoken thoughts pass between them until Dean finally breaks the gaze and clears his throat.

"So where are we anyway?"

"Somewhere near the western border of Purgatory, though I can't determine exactly where. I took an aerial scan of the area before I brought you here, to make sure it was safe. We'll have to lay low here until morning."

"Morning?" Dean questions incredulously, "You mean there's day and night here?"

"Yes. They're not sunrises and sets, as such, but there are times when it's lighter and therefore less dangerous. It's not like Hell here, Dean, it's—" he pauses, apparently searching for the right description "—more structured, in a way. There's geography, a sense of time, and even seasons. It's coming into winter now."

Dean shivers slightly at Castiel's words, only now properly acknowledging how cold he is.

"We should build a fire before you freeze," the angel states, noting Dean's shiver and the way his breath crystalises in the frigid air. "Wait here, I'll find materials we can burn".

Before Dean has a chance to reply Castiel is gone, reappearing a few seconds later with an armful of jagged looking wood, which he dumps unceremoniously at Dean's feet.

"You'll have to build it. I've never had the need for a camp fire before," Castiel explains, gesturing to the pile of wood.

Dean grins with the confidence of someone who has made a fire more times than he can count, and gets to work.

A short while later he and Castiel sit around a roaring fire, Dean warming his numb hands over the flames gratefully.

"What about you then?" Dean says, looking up at Castiel who sits beside him.

Castiel looks at him questioningly, head tilted to the side in an all too familiar gesture that Dean doesn't even realised he'd missed until now.

"I mean are you...you again?"

Castiel nods thoughtfully, stoking the fire gently with one of the longer sticks.

"I believe so, though I'm afraid I cannot offer you an explanation as to how or why. Perhaps it was the violent act of killing Dick Roman that brought me back to my senses, so to speak. But I do appear to be back in possession of my mental facilities, and I..." he pauses, lost in thought, "I'm more aware of everything that happened before...everything I did."

He stares into the flames, refusing to meet Dean's eyes. Dean shifts in his seat, knowing exactly what Castiel is referring to but really not wanting to talk about it, especially not now. He clears his throat and unsubtly changes the subject.

"So how do we get the hell out of here? I'm assuming you can't just mojo us out or we'd be gone by now."

"I'm afraid that is correct," Castiel confirms darkly. "In Purgatory my powers are weakened and, whilst they are strong enough to transport us within it's bounds, I am unable to remove us from it. We need an existing doorway between here and Earth. Creating one out of nothing is much more powerful magic than I have access to here."

Dean heaves a sigh.

"Well that's not good news."

"No," Castiel agrees. "But it's not entirely hopeless."

He picks up a small stick and starts drawing a series of lines in the dirt, and Dean moves closer to watch.

"These are the bounds of purgatory," Castiel explains, pointing to the large shape he has drawn in the ground. "The boundaries have several gates, here..." he marks a spot in the dirt, "here," he marks another, "and here. But they're treacherous, guarded by Purgatory's most powerful creatures and weapons...swarming with Leviathan and other monsters. The two of us would stand little chance against them."

Dean looks both baffled and disturbed at his words.

"I'm not hearing the good news, Cas."

Castiel looks up at him, and Dean is briefly struck by the seriousness in those eyes and how glad he is to have it back. It makes him feel strangely reassured and safe, which seems crazy all things considered.

"There is one other way," Castiel says quietly. "There is a rumoured secret portal that I may be able to open from the inside...but I hesitate to trust the source."

"Why, who was the source?" Dean questions.

"Crowley," Castiel says, practically growling the name.

Dean lets out a snort of laughter at the irony and runs a hand through his hair.

"Well given his role in us winding up here, you'll forgive me for not jumping right on that band wagon."

"I know," Castiel replies with a sigh. "But this is the closest thing we have to a plan."

Dean stares at the ground for a long moment, deep in thought.

"It's just that...it all sounds pretty uncertain, Cas," he finally says. "I mean, we're tracking down a portal we don't even know exists, and when and if we make it there alive you may not even be able to open it."

"I'm aware that it's a flawed plan," Castiel replies, a note of irritation in his voice. "But we don't have many options. We can't use the other gates and we can't run the risk of waiting for a portal to be opened from the outside."

Dean shakes his head.

"There's gotta be another option. Sammy will find a way to get us out of here. We go out there, we get ripped to shreds, you said it yourself!"

He pushes down the spike of worry in his gut when he mentions Sam's name. He knows that if he's going to get out of here alive he needs to keep his head straight— and the sooner he can escape, the sooner he can help his brother. He forces his attention back to Castiel.

"There is no other option. If we stay in here something is bound to find us eventually. And even if Sam could open a portal and could somehow communicate with us, we would still have to get to it. Trust me, Dean, this is the only way."

The pair fall into silence, Dean glowering at the fire but not bothering to argue. He's tired and cold, and if he's forced to admit it, he's also damn well scared. Trust me, Castiel had said. If only it were as simple as that. Of course, he had trusted Castiel once. He'd become one of the very few people he could trust, but he'd betrayed them and now...how can Dean trust him again? But on the other hand, what choice does he have?

Castiel seems to sense Dean's exhaustion and confusion, and his rigid expression softens slightly.

"I'm sorry that this has happened, that you've had to come here. It is not a place I ever wished you to see. But I promise you that I will get you out of here alive...or die trying."

Dean just stares for a moment, letting the words sink in, then he smirks.

"Don't die again, Cas. It's getting old."

"You're one to talk," Castiel shoots back so quickly that Dean snaps his head up to glare at him. But the angel's eyes are playful, or as close to it as they ever really get, and there's a hint of a smile playing around his mouth. Dean huffs out a laugh and Castiel allows himself a proper smile. Dean tries to ignore the fact that he feels oddly warmed by it. But all too quickly, Castiel is back to business.

"Get some sleep," he says firmly. "I'll keep watch."

Dean starts to protest, but Castiel abruptly cuts him off.

"I mean it, Dean. We have a dangerous mission tomorrow and you're no good to me sleep deprived."

Dean raises his eyebrows at the angel's bluntness, but is secretly rather pleased at the return of the no-nonsense tone that he hadn't heard in so long. It is one that he is too tired to argue with, so finally he nods and lies back against the hard ground, closing his eyes tightly and hoping that sleep will claim him quickly. If it doesn't he knows he will lie here all night, thinking and obsessing, trying (and failing) not to worry about Sam, who he is all too aware is now completely alone in a world full of demons and desperate Leviathan. After an indeterminate amount of time, Dean senses Castiel's presence beside him and cracks one eye open to peer up at him.

"Here," Castiel says quietly, shucking off his trench coat and offering it to Dean.

When Dean makes no move to take it, Castiel rolls his eyes.

"I don't require the warmth, and it will make you more comfortable."

Dean's expression softens at the gesture and he reaches up to claim the coat, though he feels inexplicably strange about it. He rolls onto his side and spreads it over himself, trying to find a more comfortable position.

"Thanks," he mutters, closing his heavy eyes. "And Cas?"

"Yes, Dean?"

"It's good to have you back."

Sleep claims him before he hears Castiel's response.