This takes place post-apocalypse (Season 6-ish). No big spoilers for the show.

Rated T for mild language and violence.

Not written as SLASH but I suppose if you really want it to be there... I'll leave that to your imagination.

First Supernatural fic, so enjoy!

Chapter One

Dean quickly stepped back as Castiel rushed past him, clutched Crowley's lapel and slammed him against the wall. It was hard enough to leave spider-web-like cracks.

Crowley scrunched up his face. "Ow."

Castiel's blade was out in a flash and pressed against Crowley's neck. "Give Sam back or I will kill you."

Crowley's dark eyes widened in mock innocence. "Not possible, angel cakes."

Dean grit his teeth in frustration. "Well then you'd better make it possible, you son of a—"

"Now, now," Crowley taunted. "Let's not get things… heated up."

With a sudden movement, he pushed Castiel backwards. Castiel stumbled back a few steps, running into Dean. He had to straighten him back up, but by then Crowley had pulled out a lighter and thrown it to the ground. There was a spark, then a circle of fire encircled both Castiel and Dean. Castiel's eyes caught Dean's in a moment of surprise.

Not one to stand idly by, Dean leapt out of the circle of flames, knowing Castiel was no use in the angel trap. He pulled out his gun and aimed it at Crowley, whose face had never looked smugger.

"Crowley!" he yelled.

Crowley raised an eyebrow. "Really? Remember how effective those salt pellets work on me?"

"Well I'm hoping they'll still hurt like hell," Dean growled. "Now let Sam go!"

Crowley curled his lips into a smile, casting his eyes to the ground as if embarrassed for his enemy. "Dean…" he nearly chuckled, looking back up at him. "You have no leverage. And—" he gestured to Castiel, "you're about to lose your warrior angel there."

Dean gripped the gun tighter. "The hell you talking about?"

Slow and precise, Crowley carefully pulled a folded piece of paper out from his suit jacket and began to unfold it. "You… know the little chant to send us demons back to Hell," he drawled slowly, "But. Do you know the one for angels?"

"There isn't one." Anxiety began to clutch at Dean. No, he had never heard of any way other than painting blood on the wall to get rid of an angel.

"Oh but there is. I can draw Castiel right out of his vessel and send him back to his harp playing in the clouds with a few Latin words. Uncannily similar to how you send us back downstairs. Same concept anyway."

Dean looked back at Castiel, who locked his gaze. "Is he serious? This is a thing?"

He didn't reply, but the slight nod and intensity in his blazing blue eyes confirmed that it was.

"There now," Crowley said, "If you'll excuse me…"

And Dean was thrown hard against a wall. Trying to force his body to take a breath of air, he faintly heard Crowley begin to read from the paper. No. He wasn't getting rid of Cas. Not on his watch.

He tried to stand. The world spun so fast he thought he would be sick.

"Dean."

He heard Castiel's voice, but couldn't focus. He tried again to stand. "Cas…" he wheezed.

Past the black stars that spotted his vision, he saw Castiel standing only ten feet away from him, staring him down and twitching his hand in his direction. Confusion bounced around in Dean's head. "Cas… what…?"

He was pointing at something. Looking to his left, Dean saw it—a wooden plank. He needed to get that over the flames. He crawled towards it. Crowley was either too busy chanting off his paper to notice, or didn't really care. Dean heard a low gasp, and Castiel suddenly crumpled to the ground.

Knowing time was about up, Dean pushed himself up to his knees and grabbed the plank. His vision was clearing now. With a shove, he pushed the plank across the flames.

But by now Castiel was curled into a fetal position, jerking and writhing as Crowley neared the end of his chant. He managed to lift his head to meet Dean's gaze and reach out a hand. "Dean." He writhed in another bout of anguish, then stretched his hand out again. His next words were through clenched teeth.

"I need your permission…" He began shaking uncontrollably.

Dean thought about getting up and pouncing on Crowley, but he knew it would do no good. So he reached across the plank and clutched Castiel's hand. It was slick with sweat and radiating with painful heat. His eyes were beginning to glow.

He tried again.

"I need you to be my vessel," he growled.

Dean tried to comprehend what he just said. "…What?"

Castiel shuddered and began to convulse. Dean kept a tight grip on his hand. "Just…. Say…. Yes."

Everything clicked together. Dean hesitated for a split second. Having an angel in his body was the last thing he wanted to do. But if it would save them…

"Just find Sammy!" Dean growled. "And kick Crowley's-"

Castiel's eyes suddenly beamed light too bright to look at, and Dean ducked his head, heart thumping. Were they too late? Was Cas gone?

The light grew so bright that it burned through Dean's eyelids.

And then there was a deep deep darkness shrouded in ringing silence.