Castiel didn't risk checking on Dean until Sam had already called to say he was returning with the blood. The night before had been spent largely outside the bunker, watching the stars and trying to get a handle on his emotions. He wasn't sure he had managed that.

He had made the mistake of watching some of the news reports covering the disaster on the east coast, and he was thoroughly shaken up.

Even now, the angel hesitated before finally opening the door to 7b, and walking in to face the bound Knight of Hell.

Dean looked up as the lights flickered on, black eyes leveling their gaze on the angel. "Castiel."

Cas felt a familiar shudder down his spine. In days past Dean repeatedly fell back on his full name, something before he had only done in formal prayer. This was a clear choice, a coldness that the demon was pulling out either to distance them or just because he knew it got under his skin. "Hello Dean." He replied simply.

"I see Sam has not returned yet." Dean tested. "It still isn't too late to let me go."

"And what possible reason do you think could convince me to do that?" Cas asked, sinking into the chair in the corner, keeping the metal table between him and the demon.

"Oh, come now. There are plenty of reasons not to do this. We shared something special the other night. You know me, the human me never would have had the stones to break you down like that." He grinned. "And I know you enjoyed yourself."

"Not a compelling enough reason to free you."

"We could leave. You and me. No bunker, no angels. Find somewhere far away."

Cas shook his head. "No thank you."

Dean rolled his eyes. "Come on Castiel. We'd have eternity to figure this out." He insisted. "You turn me back, where does that leave me? Human? Great. Best case scenario you keep me locked up until I die of old age and it's right back to black eyes and blood."

"We'll find a way to remove the mark."

Dean snorted a laugh. "Sure. I bet that will work."

"The real you would never want to be this way."

"The so-called real me is dead, and he isn't coming back. And you know that." Dean responded darkly. "You know that."

Sam's voice sounded from the doorway. "Well, we'll see."

"Ooh. Cooler full of blood. Perfect." Dean spat, rolling his eyes.

"For what it's worth, I got your blood type."

"You don't even know if this is going to work. Knight of Hell, Mark of Cain. There's no telling if this will even do a damn thing to me."

"Well, guess we'll find out." Sam already had the syringe out and ready to start.

Cas clamped Dean's shoulder still so Sam had a stationary target to aim for. Once the injection was finished, they both stood back, watching as Dean's cocky grin gave way to a twisted grimace of pain. After it seemed to clear, they both walked from the room, regrouping in the hallway.

"Kevin?" Cas asked.

"Watching the camera feed from the library." Sam replied. "Thought it was best he had some distance."

The angel nodded thoughtfully.

Sam frowned. "Did you see that? The way it seemed to hurt him?"

"That wasn't what it was like with Crowley?"

"No." Sam shifted his weight. "He was pissed we were doing it, but it didn't seem to cause him pain."

"He may be doing it just to mess with your head."

"Yeah." Sam replied absently.

"What now?"

Sam looked back towards the door. "Next dose is in an hour. We shouldn't leave him alone."

"I'll stay with him. You go." Cas encouraged.

Sam looked like he might argue for a second, but he nodded, turning and heading back towards the library to check in on Kevin.

Castiel sighed, composing himself for a moment before walking back into the room where the hunter sat. "Eight more hours and you'll be back to normal."

"Eight more hours until you basically kill me then." Dean growled.

"We're freeing you, Dean."

"Oh cut the crap, Cas." Dean snapped. "If you thought that Dean was broken before, what the fuck do you think will happen if I return to him with all this fresh blood on my hands?"

Cas looked away. Of course, he had thought of that.

"Oh? No defense? You know then. You're well aware that whatever you bring back may be technically alive, but will never be a functioning person ever again. At best you're looking at insanity, but realistically you can toss a coin between coma and suicidal mess."

"Dean, you've always been stronger than you give yourself credit for."

"Look me in the eyes, right now, and tell me you think I'll be able to recover from that."

Castiel did not even try to meet his eyes. "We will deal with the fallout. Whatever it may be."

"Great. Just fantastic."

.

The following treatments seemed to pass with similar difficulties. Each time Dean lost a little color, looked a little sicker. Each time the pain seemed to mount. But still afterwards he was there to pull out the snark and the bite.

Each time both Cas and Sam fought to hide their growing concern and unease.

Sam pulled Cas outside right before injection number seven. He looked back at the closed door before turning towards Cas. He kept his voice hushed. "Is it just me, or is this not working?"

"I am unsure." The angel admitted.

"Crowley at this point at least seemed different. And he didn't look like he was one foot in the grave."

"The mark of Cain is likely changing the way this works."

"Cas, what if this really is killing him. Like… beyond the mark, actually dead?"

Cas looked at Sam, sympathy clearly read in his eyes. "It may be."

"So...do we stop?"

"And do what? We can't leave him like this. This is the only way. Either it works…"

"Or it kills him." Sam closed his eyes, leaning his head back against the cool tile. He hesitated, debating whether or not to bring up what he overheard. He looked up at the angel. "Do you think he was right? That he won't be able to handle it when he's human."

The angel hesitated again, avoiding looking right at Sam. "I don't know. Dean always has felt sorrow so profoundly."

"He killed thousands... " Sam breathed. "After hell he was never quite the same, and it took him months after purgatory to be more or less alright. What if this is one he can't recover from?"

"I don't have any answers, Sam." Cas replied, his voice strained.

The younger Winchester sighed. "Yeah… I know. I'm sorry… I know this has got to be shit for you too."

"We'll see this through, and then deal with whatever consequences there are after." Cas said firmly, trying to regain his earlier conviction.

Sam nodded, opening the door and starting back inside. He froze as he saw Dean sitting, head completely limp. "Dean?" He hurried in, coming up to him. No response. He shook the demon slightly, then harder, slapping him before Dean so much as stirred. "Hey… you okay?"

"Yeah. Sure. I'm great." Came the slightly slurred sarcastic response.

Sam straightened up, shaking slightly as he moved to prepare the next injection. Cas watched from the doorway as he readied the syringe. "Look, We can't stop doing this."

"Sure you can. You just stop. There's no point in trying to bring your brother back now."

"We will bring him back."

"I've been trying to tell Cas, your brother is too fragile to handle this."

"Yeah, I heard." Sam said, unconsciously flicking his eyes up to the webcam.

Dean followed his gaze, noticing the device for the first time. He stared at it a moment before looking back to Sam. "You don't get it, Sam. Poor sheltered Sam. Too stupid to see it Sam." the demon sneered. "You don't even know half the things about my life. When I was growing up I thought I had just managed to hide it well enough, but as I got older it became obvious that you just didn't care enough to pay attention."

"That isn't true." Sam said, keeping his voice even and indifferent.

"No? So it was just my imagination." Dean knew he hit a nerve. "Your very existence sucked the life out of my life. I never had a childhood. You never questioned it. You don't even know half the things I did to keep food on the table. Stealing was the least horrific thing I ever lowered myself to. But you got fed, who cares where it came from." He shook his head. "Sam, I went to hell, for forty years for you, and you what, shed a tear when I told you? Then moved on?"

"This is just you trying to trick me into stopping, and it isn't going to work." Sam walked forward with the blood in hand.

"Your brother has been barely avoiding being crushed by everything that's ever happened to him his entire life." Dean glared as he didn't slow down. "Sam-"

The hunter didn't break stride, injecting him before he threw the needle and walked out.

Cas looked back for another moment, watching Dean writhe against his restraints in pain before turning and following after Sam.

The younger Winchester didn't stop moving until he reached the kitchen, splashing some water on his face and coming to lean against the counter. "He's right." He muttered.

"No Sam, he isn't. He's just trying to provoke you."

Sam took a deep measured breath. "Yeah. I know. On some level, I know It's just-"

"Hard to remember when it's Dean who is saying it?" Cas frowned. "I know."

"Yeah." Sam gave a weak humorless laugh.

"Sam-"

A noise from across the bunker had them both turning their heads. They looked at each other, dread mounting in their chest, though they didn't yet know why. Without saying anything both were rushing back towards 7b.

Sam rounded the corner first, skidding to a stop when he found the chair that once held Dean empty.

Cas stopped just inside the door, looking at Sam and then around the room. He followed Sam as he started to run across the bunker. "We need to stop him from getting out." Sam said breathlessly.

"I know." Cas agreed.

Sam hopped over the steps down into the electrical room, throwing open the metal cage door and slamming the breaker down. The bunker locked down, lights cutting to the emergency red. "That will lock the door. Now we just have to find him." He heard a cry for help echoing from down the hallway. "Kevin…" Sam breathed, turning and starting to run back towards the library.

Both men stopped as soon as they reached the library, freezing as the dread mounted in their chests.

In the middle of the eerily lit room stood Dean, one arm on the prophet's shoulder, the other holding an angel blade to the side of his neck. "Hey guys." He greeted, a twisted grin on his lips.

"Dean, put the knife down." Sam's voice was firm, and his hands were raised slightly, ready to react.

"Gladly. One of you turns the power back on, and opens the front door and I'll be happy to be on my merry way. You can keep god's librarian."

"Dean… let Kevin go." Cas tried, stepping forward with Sam, very slowly. He stopped again as Dean pressed the blade forward, just barely cutting into Kevin's neck, eliciting a hiss of pain.

"I'm not going to sit around and wait to suffer some painful terrible fate. I'm going to leave. Listen guys, I'm even willing to deal. You want to keep the first blade? Fair compromise. Less temptation, less damage, right?" He shook his head slowly. "I promise to be good. If the father of murder can settle down than why not let me?"

"Dean, let Kevin go." Sam repeated.

"The door. Now." Dean countered.

Sam's voice strengthened. "You know we can't do that."

Dean looked down at the knife against Kevin's neck. "Yeah. I do." His eyes snapped up to lock with Sam's and his hand thrust sideways, piercing through the prophet's neck. Sam and Cas both shouted. The demon pulled the blade back out, blood spraying across him and the library table. He readied himself as both hunter and angel began to advance on him.

Sam reached him first, striking to try and get the angel blade out of Dean's hands. The older Winchester was ready, knocking him back and slashing out with the weapon, catching Sam across the chest, not yet deep enough to maim him.

Cas lunged at the hunter, but Dean managed to push him back and off balance.

Sam reared up for another attack but found himself kicked backwards, falling to the ground with his brother standing over him. Dean raised his arm, and Sam closed his eyes, getting ready for the blade that was about to thrust through his chest.

Castiel reacted quick and decisive, exerting more strength than he'd ever used on the hunter. He punched forward, directly into the demon's chest, sending him flying backwards with a crack.

Dean crashed into one of the bookshelves, wood splintering and books scattering. The older hunter slid to the ground bonelessly, though Cas honestly couldn't tell if he was unconscious or dead.

Sam was already scrambling sideways across the ground, following the excessive river of blood back to the prophet. "Kevin!?" Sam tried to place his hand over the still sluggishly bleeding wound, but he didn't stir at all.

Cas rushed to kneel beside them, wasting no time putting his hand on Kevin's chest, pooling his grace and pushing it forward, gripping the last shreds of Kevin's hold on life and forcing them back into place. He felt his way towards the injury, knitting the flesh back together and regenerating the lost blood. He retracted his hand, relieved as the prophet took a deep desperate breath before dissolving into a fit of coughs.

Sam half collapsed with relief, hardly noticing as the angel laid a hand on his shoulder and his chest wound sealed shut. After a moment he tensed, his brain catching up. He looked back at Dean.

Cas was already on his way back, and he tentatively sank to one knee beside the hunter. Putting a hand out, it was clear to him the hunter's rib cage was broken, as was his neck, not to mention the split and bleeding gash on the back of his skull. Cas continued to probe with his grace until he could be sure his demonic healing was slowly working on sorting through the massive amount of damage. He looked up at Sam and gave him a nod. Dean was alive at least.

Castiel reluctantly put an arm around Dean's battered torso and pulled him from the splinters and dust, carrying him back towards the devils trap.

Sam squeezed Kevin's shoulder, giving him a sympathetic glance as he saw the prophet begin to crumble. He couldn't wait with him though, he knew he had to help restrain Dean properly this time. He jogged after Cas.

"We will need to secure him more thoroughly this time." Cas said softly, unable to process what just happened.

"How the hell did he even get out to begin with?" Sam asked breathlessly, his legs shaky as he walked to the side of the room, readying some more heavy duty shackles.

"I'm guessing the treatment is working. The more human he becomes, the less he is affected by the magicks that are infused into the sigils."

Sam let the words sink in. "He only has one more injection…" He swallowed. "If he's so close to human, then why could he still… why did he still…"

"I don't know." Castiel breathed. He stepped back as Sam continued to lock down the demon.

Dean did not regain consciousness until just a few moments before the final injection.

Both Cas and Sam sat leaning against the metal table. Sam's arms were crossed as he carefully kept an eye on the stirring demon.

Cas just shifted uncomfortably. He had been monitoring his progress in healing, but he still had been anxious to see Dean move.

Dean looked up at them, his expression only slightly hostile. "Please. I'm begging you. Don't do this."

"You...Dean would want this. To be cured, whatever the consequences." Sam said softly.

"No. I wouldn't. I'm here and saying don't do it."

"You're not Dean." Sam slid the final needle into his arm.

Cas looked away from the hunter's agony, unable to watch his expression as the fire spread up his arm. When the sound stopped he let himself look up at the now slack hunter.

Sam stepped forward, pressing two fingers to his brother's neck. He was reassured by the steady heartbeat he got in return. He made a hasty retreat when Dean stirred.

The hunter brought his head up, unfocused gaze settled somewhere between the two men. His black eyes dissolved into green. He looked from Sam to Cas and almost in a daze muttered, "You look worried, fellas."

Sam looked back at Cas, hand reaching into his pocket. He pulled out a small flask of holy water, flicking it at his brother, his posture relaxing as there was no reaction. He let out his breath. "Welcome back, Dean."

Dean looked around himself, still in a daze, but Cas could see when his memories started to quickly flood back.

Sam watched as Dean's eyes sharpened right before his breath caught in his throat. The younger Winchester frowned as Dean shuddered, but was unable to inhale again. He watched his brother's eyes widen, focus off in the distance. Entirely unable to breathe.