Full series summary:

It has been months since Dean was brought back from Hell to greet a world on the brink of the war to end all wars. The forces of both Heaven and Hell prepare for one, final stand off to determine the fate of the world. The Seals are being broken and have only just reached the halfway mark.

For reasons undisclosed to the brothers, demons have suddenly taken an interest in Dean. Not long goes by that one doesn't try and capture him. What happens when Sam and Dean's roles are reversed and it is Dean who needs protecting?

Meanwhile, Sam is plagued by crippling attacks which seem to rub off a little more of himself with every second. He is soon on the edge of loosing himself. Can Dean pull him back?

As the end of all ends approaches, the boys are tried in new and old ways. Some new things appear. Old threats return. Some old ones gain new faces. New allies are created. Old bridges are burned.

Can things ever be the same?

Episode 1: Shadows Gather

Part 1: Cryptic Warnings

Part 2: A Dark Secret

Though the battle is impending, the boys realize there is no use in sitting around, waiting for it. So they go off in search of a new hunt. It's not long before the promise of a case draws them in. But turmoil between the pair rises when it is divulged that both aren't exactly being truthful...

Dean looked at the road before him. No lights, no cars, not another person in sight. There hadn't been for miles. Just clean open road. The night had came and went as the predawn white, unearthly light washed over the endless empty grey line of road midst the white gold sand. It did him good to be able to relax and not worry. Not worry about other drivers. Not worry about demons. Not worry about the impending battle….

Not worry about Sam.

He glanced over to the passenger seat. His brother lay with his head against the window; sleeping with his mouth hung agape, drool dripping from young, full lips. He let out a soft moan and squirmed his legs slightly as he further pressed against the window, his peach cheek flat. A long scar running down his other cheek darkened Dean's train of thought for a moment, but no longer. Other than that, his visible skin was unbroken. But Dean knew better. There were endless scrapes and scars lying beneath the clothes he dawned. Even still, lying there so peacefully, it had a comical effect.

He couldn't help but chuckle a little. And this was who all those angels and demons are afraid of? It was hard to believe he, as the slightly-feminine, superstitious little boy he was, could lift a dang finger to them. He'd always seemed softer then Dean. Maybe it was just his youth, but Dean doubted it. At his age, Dean had already whipped through a hundreds of spirits and quite a few demons.

And then he thought of last night. The thirty-third seal. The half way marker. Essence of truth. He shuddered as the thought came. Everything in the deepest corners of his mind, assaulting him at once. And all of his thoughts and secrets revealed to anyone who could control their own mind enough to glimpse his.

That whole day, he and Sam stayed at an almost vacant hotel, hoping to hide their thoughts by going into seclusion. Dean had also lined their room with salt and marked a few devil's traps on the ceilings and walls with the hopes that with their own minds disrupted, their enemies would not think clearly enough to breech such basic defense. But that hadn't been his worst worry at the time, truth be told. Sam had.

At first, it almost seemed not to affect him and Dean wondered if it was the demon's blood which had made it so. That is, till Dean pretty well had his own mind under control and glance over at Sam's. He could feel his tenseness, trying to protect his inter most self from the whole world's eyes. Like a bursting dam, he failed and every slip up, every mistake, every bit of pain, all of it coursing out. The thought that one day he might be something he's not. That he might do things that weren't him. Every damn little thing those son-of-a-bitch demons and anyone else had ever tried to shove into his little head.

But what surprised and shocked Dean was the presence of something about Sam he hadn't known. Before he got a detailed look, Sam started to seizure, but he still saw a bit. It was like something was grinding away who his brother was. And then there was…

A shadow.

He didn't get much further, but chills ran down his back. What was going on in his younger brother's head? He had to wonder…Sam had run off shortly after that and Dean hadn't known where he went. When he finally found him, he was in sheer hysteria. He had needed Bobby's help to calm him and as a result, Sam had slightly pulled his shoulder.

If you can't save him, you'll have to kill him.

The words resonated through his head, clear as the day his father had told him before he died. They stunned him, making him feel anxious and unsteady.

Dean shook his head. "No, if it came down to it, baby brother, I'd be more likely to let you destroy me and this world before I cut away your life." He said quietly.

Damn it! Why the hell did this always need to be on his mind? It was those dang angels. It seemed like not a day went by that they hadn't seen fit to remind him of Castiel's promise, that if he didn't stop Sam, they would. Always, whether through some sign, an omen, or one of those sons-of-a-bitches coming down to say it to his face. And he was trying. But, how do you save someone from such a fate?

He pounded one of his fists on the dash, grunting. Sam suddenly flung up, the noise stirring him from his deep sleep. "What! Huh!" He slugged out wearily. He looked to the source of the sudden noise. Those big, luminous hazel eyes gazed at his face. "What's wrong?"

"Nothing." Dean lied. "How ya feeling, Sammy?" Sam gave him a look that he'd learned meant one thing. I don't believe you. It lasted a long, hard moment.

But still, he answered after a time. "My arm hurts a little."

"Well, it should. I can't believe how hard you can be to calm sometimes. Took both me and Bobby to get you relaxed after the seal was over. I'm sorry if we hurt your arm a little. You're just like a little girl sometimes."

"Jerk." Sam replied, smiling.

"Bitch." He grinned back. The two both chortled a little, looking off their separate ways as they always did.

Then something hit him. It was moments like these he always cherished. It was these memories that had kept him from dying in the hospital what seems like so long ago. It was moments like these that had made him make the choice he made, to sell his soul in exchange for his brother's life. It was moments like these that kept him from becoming a demon in Hell. It was them…and Sam.

He glanced over to him. Sam's eyes were flashing slightly, like he was thinking about something. There was some sort of pain, and anguish grained on his face. He saw Dean watching and quickly changed it to a fake smile, but the look was still there, just muffled a little.

He tried to avert Dean's attentions. "So, where are we?" He asked, looking around at the desolate, unmarked landscape.

Dean shrugged. "I don't know. Somewhere in Nevada. Probably getting towards the border to California."

"Huh…how long till we're there?" Sam asked.

"Beats me. Could be another five or six hours." Sam let out a groan, as if the thought of only five hours was far too long. His hair was mussed up and he rubbed his hands across his face then through his hair, making it straighten out to a degree. "Listen. You need to get some sleep. You look like you've just been to Hell and back. And trust me. I know what that looks like. I did look in the mirror at that hotel…"

Sam did not seem amused. He only gave Dean a strange look, the shot back, "You need to sleep too. You don't exactly look like that chick back in Mirronto either."

Dean smiled at the thought. "She was fine, wasn't she?" Sam sighed.

"You know, I've driven her before. You don't think all those times that I had to save your ass was enough experience with the Impala?"

"Ya, ya, ya. I'm not tired at all. And to all honesty, I'd rather wait till we get to a hotel and crash for a while. This road isn't exactly glass." Even as he said this, they past over a particularly nasty pothole. The impact smashed Sam's head against the window. Dean chuckled while he rubbed his head. "As I had said, I'll pass. But we are going to need to start working as soon as we get there. Since you are already half rested, go back to sleep. I'll wake you if we stop."

Sam eyed him before reluctantly closing his eyes. It wasn't too long before his deep, telltale breathing said asleep. For a while longer, Dean drove without rest, focusing on the road as the only car they'd seen for miles, a bent-up old ford, passed them.

Then, once more it was more open road and the endless Nevada desert. A gust of wind picked up the white gold sand, swirling it in the air.

Suddenly, with out warning, lights flickered in his car in a rapid display. His windshield wipers clicked on and off and back on on their own accord. The Impala's headlights began to flash rapidly, and sparks showering the road. A storm hit suddenly, turning the skies black. Lightning crackled as the thunder let a loud bang fill Dean's ears.

Dean sighed. Reminder time again. Where are you, you little bustard? As if in answer, there came a noise from inside the Impala. Instinctively, he searched for its source in the back seat. But there was no one back there. There was no one else anywhere. It was just Dean and Sam in the Impala.

A hand suddenly touched his arm. Alarmed, he swerved to the side of the road, pulling over. "Jesus." He muttered, straightening out the wheel. The hand's grip on his arm never faltered, never swayed. Nor did its owner speak till he looked over.

It was Sam. He was confused for a moment. That is, till he saw the shadow of wings behind his back.

"You possessed Sam?" He said shocked. "You son-of-a-"

In a sharp, inhuman nod, Castiel spoke with Sam's lips. "I needed to speak with you…and find out his status."

"If you hurt him, I swear I'll…" Dean started.

"You'll what? Kill me? While I'm in Sam's body?" Castiel answered. "Besides, he's fine. To him, he's still sleeping. He won't even know I was here. And it will stay as such unless tell him."

Dean heaved a great sigh. Why did this kind of thing always happen to Sam more than it ever did to him? "Fine. But I was under the impression that we were impervious to possession."

"Demonic, yes. Angelic, no. Angelic possession is different." Castiel answered. Some how, the tone of Sam's voice seemed different. Smooth, rich, calm.

"How is it different at all? You take some poor bustard's body as a meat puppet. Demons do the exact same. How can you say it's different?"

"You may know more about possession than most anyone alive, but you still know nothing." Castiel answered. "All the symbols, hexes, charms you and Sam posses or have placed upon yourselves were and will always be wards against demons. Angels are different. Demons may have mimicked our design, but they have done it in different ways."

Dean gave an amused look. "Note to self, get some anti-angel charms."

Castiel was not amused. "Dean. You never will change will you." For a moment, Dean forgot who he was talking to by that all too familiar phrase. The real Sam always said that.

"As much fun as this has been, I would like my brother back soon here. Don't get me wrong, I love that you haven't gone all cryptic on me. But don't tell me you came down here and possessed my brother just for a little chit chat about the differences between demonic and angelic possession. What do you really need to say? It's getting creepy, hearing you use Sam's voice that way…"

For the first time Dean had ever seen, Castiel gave a short smirk. Gone in the blink of an eye, but still. Then Castiel gave another sharp nod. Dean winced. If he kept doing that, Sam was going to get whiplash. But the next moment he spoke. "I'll try and make this short." Castiel froze, as if thinking. His eyes just seemed to stare off blankly into space. A shudder went down Dean's spine as he realized how unlikely it was that Castiel was searching his own thoughts that hard.

A strange light suddenly appeared in his eyes. It wasn't fear, but it was about the most dismayed Dean had seen him. For all the times that he'd came to warn Dean, there was something different about his behavior. Like he was…sad…about something.

"You're running out of time. We're loosing him. The further he goes, the more he changes. Before it's too late, take care of him, Dean."

"And how, pray tell am I supposed to do that?" Dean yelled. "Tell me! I don't know what to do. You've told me over and over again the same damn thing! I don't know how to save him! So quit with this charade and tell me how to save Sam! I'll do it, you know! What ever you need me to do. Shoot some son-of-a-bitch, use some magical leeches to suck out the demon blood. Whatever!"

Dean heaved his breathes. His heart beet rapidly. Tears had weld up in his eyes, blurring his vision. He caught a glimpse of his face in the mirror. Blood had rushed to his face, turning it flushed slightly.

Castiel simply sat there, silent, holding his head with the tips of his fingers. His face belied little emotion. Finally, he spoke, his voice calm, quiet, deliberate, and smooth as a lake on a windless, boat-less day. "Dean, this is something you must learn for yourself. There's only so much I am allowed to tell you. But you need to calm yourself. You will do nothing for Sam by screaming at the one person who's trying to help you figure out what to do."

Dean sighed. It was true. He felt a slightly embarrassed. He didn't know enough about angels to try and force answers out of them.

Castiel seemed lost thought, his own hopefully this time. It was like he was there with Dean physically, but not in his mind.

He suddenly spoke once more. "I'm afraid I must leave, Dean. I need to report to my boss. Something new has presented itself."

Dean nodded and murmured his goodbyes. In an instant, Castiel was gone. Sam was back asleep. Though he began to stir as Dean revved the engine and pulled back onto the road.

Sam moaned. "Why'd we stop?"

"One of the tires was acting up a little." Dean responded. "Guess it was just my imagination."

"Uh. What happened? It feels like a train hit my neck…" Dean stifled a chuckle. If only he knew. If only he knew.