A/N: This was requested on Tumblr by thedemonofcat. They wanted a "Winter Soldier" inspired story where Cas had trigger words thanks to Naomi's programming that would turn him into a killing machine. The prompt was supposed to be a drabble, but it ended up being way too much to fit into such a small space! So here's a one-shot instead ^_^

Thanks to the always wonderful Aini Nufire for helping me sort this out, you're the best beta ever!

Setting: S8, sometime after the Naomi business.

"Apple. Water. Sandstorm. Forge. Millions."

Dean had no idea what those words had meant. He only knew what they'd achieved. With a strangled yell, the hunter ducked just in time.

"What the hell was that about?" he demanded of the angel who uttered them, their enemy pinned down in the ring of holy fire.

The angel didn't answer, only smirked and looked past Dean.

"Sam!" he wheezed, but his brother was down for the count. Dean barely dodged another blow, tripping sideways without enough time to recover. A hand clutched at his jacket and slammed him into the wall.

Dean turned and saw Cas straighten rigidly. The warrior's face became blank. His eyes emptied. Everything that made him CAS had disappeared.

"Ready for orders."

Dean's heart stopped.

"Cas!" Too late. He couldn't avoid the fist connecting with his jaw. If Cas still had his full power, the strike would have shattered bone. As it was, Dean grunted in pain, seeing stars. "Cas, s-stop! It's me-"

He was cut off again by another blow, this time darkening his vision for a few terrifying seconds.

"Cas?" Sam demanded, looking between their captive and their angel friend. "What are you-"

"These humans are blasphemers," the other angel said over him. "Kill them, Castiel."

"Cas, please," Dean gurgled through a mouthful of blood. Memories of their fight in the crypt resurfaced, haunting and unstoppable. Like Cas. But this time they didn't have the tablet to break, releasing their friend from whatever spell this was. He remembered Cas beating him down, raising the angel blade, how he paused when Dean tried to plead with him.

That didn't seem to have any effect this time, though.

"Oh, like he's gonna listen to you?" Dean scoffed at the captive angel, only a second before Cas grabbed him from behind and threw him across the room.

The other angel cackled. "Did you think Naomi hadn't programmed any subroutines as a contingency?"

Dean watched as Sam tried to grab Cas's arm, only to be hit so hard he crumpled to the ground.

And now their best friend was trying to kill them. Dean crawled backwards, pressed against the wall, hand raised uselessly to ward the angel off. "Cas," he tried again. "It's Dean. We're your family! You don't want to do this, I know you're in there. You can beat this!"

"I don't know you."

Dean's breath hitched in choked agony that had nothing to do with the throbbing in his face. No, no, no… anything but this.

"You do know me," Dean pleaded. "Your name is Cas and you-"

"My name is Castiel."

"-you're my best friend. You're an angel, but you help people. You helped us stop the Apocalypse. Cas, come on, fight it!"

For a second, Cas stopped, but there was no trace of recognition in his face. Only his hand moved, dropping to his side as a blade slithered down into his grip. The last time Dean's heart had shattered this hard, Lucifer was wearing his baby brother.

"Cas, no," Sam mumbled weakly, peeling himself back to consciousness. Nearby, something metal clattered to the floor, tossed their way from the fiery ring.

"There's only one way to stop him," the other angel hummed.

The metal thing on the floor was an angel blade.

"No!" Dean roared as Sam scrambled forward without hesitation, scooped it up, lunged. "Sammy, NO!"

But no pointed blade punched its way through Cas's shirt. No shocked grunt or look of surprise. No blood spattered across Dean's face. Instead, he heard a heavy thump as Sam swung the pommel end with all his might into the back of Cas's head, and the angel went down hard.

Sam was breathing heavily, but gave Dean a wounded look. "You know I wouldn't."

He did know. It was just panic in the moment making him lose his head. With an apologetic nod, he turned back to their angel.

"Cas," Dean whispered, crawling forward to grab his friend's arm and roll him onto his back. Cas's eyes were closed, but he was breathing as Dean kicked his angel blade away. "Sam, the holy oil!"

The other angel was glowering as Sam raced to grab the jug they'd used to trap him; Dean knew the bastard had been hoping they would kill Cas, and he was going to wish he hadn't.

Sam poured the holy oil in a circle around Dean and Cas. Only then did Dean leave his friend's side, reluctantly stepping outside of the ring while Sam lit it on fire. The flames rose with a whoosh, painting the downed angel's face orange and gold.

Only just in time, as Cas blinked his eyes open, then leaped to his feet with the same empty stare.

"You can't contain me forever."

"What did you do to him?" Dean demanded, storming towards the other angel. "That thing you said earlier, what was that?"

"I activated the kill program Naomi embedded," the angel answered readily, smirk laden with hatred. "He was never free, Winchester. He still belongs to us. He always will."

"He doesn't belong to anyone," Sam snarled in return. "Turn it off!"

The angel only smiled and crossed his arms. "Let me out of here, then we'll talk."

Dean's hands clenched into fists. Retrieving Cas's blade, he moved slowly and deliberately to the jug of remaining oil.

"Or," he said, low and deadly as he poured a slow trickle of the oil over the glinting blade. "We do this my way." By the time he turned back to the angel, Dean was smiling coldly. "Maybe you haven't heard, but I'm very… very good at this."

And for Cas, there was no level he wouldn't sink to and no torture he wouldn't commit. From the look on the angel's face, he knew it, too, but he shook his head.

"I'd suffer anything to watch the traitor die. Or kill you. I'm happy with either."

"Wrong answer."

The ring of fire surrounding the angel was small enough to keep him well within arm's length. Dean thrust the blade through the flames, the heavenly metal igniting as it went, plunging straight into the angel's abdomen.

The walls shook with the force of the angel's true voice screaming in agony; Sam ducked, covering his ears at the sound, but Dean's hardened glare only deepened. He ripped the blade back out, ignoring the painful heat. A quick look over his shoulder told Dean that Cas was watching impartially, unconcerned about his sibling's suffering or his own prison.

"Well?" the hunter snarled.

"N-no."

"Fine." Again, the blade flashed. This time, it pierced all the way through his upper chest, a flame flaring up only to be smothered again by the angel's insides where it could scorch the true form within. Blood and grace glinted on the metal as the angel howled.

"Turn it off!" Dean bellowed over his cries. He raised the blade again, but the angel held up a hand.

"Wait! Wait… Alright…" Coughing on blood, the angel choked out, "Our will be done."

Dean whirled in time to see Cas's eyes roll back, body jerking in a violent spasm. He raced over with Sam right behind him. For a horrible moment, he thought Cas might fall into a full-blown seizure, and what if he rolled right into the flames? But then the fit passed and Cas slumped forward, pressing his hands into his legs.

Then, slowly, he raised his eyes and registered the fire.

Cas froze. Dean saw his breath quicken as his gaze locked onto the still bloody angel blade in Dean's hand.

"Dean," Cas whispered hoarsely. "What are you doing?" He took a step back; the fear in his face twisted Dean's heart. "I don't understand…"

"Cas!" Sam gasped as Dean hurried to toss the weapon aside. "Hold on, we'll get you out of there."

He raced out the door, but Cas still appeared disoriented, turning in a circle to see his fiery prison.

"Dean," he pleaded softly. "What's going on?"

"It's okay," Dean assured him, holding up a hand. "Hey, look at me."

"What happened to you? How did I get in here?"

"It's okay," Dean repeated. He glowered over his shoulder at the quietly sobbing prisoner, then turned his attention back to Cas where it belonged. "We got you back, that's all that matters."

The angel didn't reply, eyes searching Dean's face, which was probably already turning some impressive colors. Dean saw the dawning realization, saw it in Cas's expression as one fear shifted rapidly into a brand new one.

He shook his head. "Cas, everyone's fine-"

"It was me, wasn't it? I did that to you. What did I do?"

With a sigh, the hunter relented. "Me and Sammy got knocked around a bit, but it's nothing we can't handle. We're fine. Cas, it wasn't you."

"It was. I did this…" Cas's hands surged up, clasping the back of his head as his eyes glazed with moisture. "I don't- I didn't…"

"It wasn't your fault," Sam assured him as he hurried back over with a fire extinguisher from the Impala. "We know that."

Cas didn't speak as Sam grimly put out the fire that penned him in, nor did he look at either of them. When the flames were gone, he stepped stiffly away, arms wrapping around himself.

"Dean, get him out," Sam urged softly, retrieving Cas's blade. His eyes turned towards the angel prisoner still whimpering in his own fiery ring. "I'll finish up in here."

Though Dean would have loved to end the bastard himself, he was more concerned about Cas. Giving Sam a dark nod, he took his friend's arm and propelled him out of the building into the fresh air.

As soon as they'd crossed the threshold, Cas whirled and pulled away from Dean.

"What happened?" he demanded, voice shaky. "One minute we were interrogating Elijah, then you're bloody and bruised, and I'm in a ring of holy fire."

Dean watched his friend's face, frowning. "Whatever it was he said, that program he activated-"

"What program? What did he say?"

Slowly, Dean shook his head. "You remember none of this?"

"No! What did he say?"

"Just a bunch of random words. I don't know. It was some kind of trigger. Naomi programmed you so when he said the right things, it turned you into soldier boy. He told you to kill us, so you gave it a good try. You seriously don't remember."

Cas turned his back, hands raking through his hair. "Naomi," he spat. "I thought I was free of her."

"He was never free, Winchester."

Dean swallowed, barely holding back his rage at what those angels had done to his best friend. He wished it were Naomi herself that he had at his mercy.

"You, uh… had no idea who we were, either," he went on. "I don't know, man. Whatever that program is, it turns you into… not you. It wasn't your fault."

"Tell that to the people I might have hurt!" Cas spat with bitter vitriol. "You think it matters whether I knew what I was doing or not? It's still on my hands! How long ago did she… program me?"

"He didn't say."

"How am I out of it now?"

Dean shrugged. "I persuaded him to say the super secret 'power off' phrase."

All the fight seemed to leave Cas, back still turned as he dropped his hands and slumped. For a long moment, he was silent, then finally murmured, "So he only turned it off. He didn't… un-program me."

"I guess not."

Another moment of silence. Then: "So any angel who knows the trigger words can still use me."

Exhaling heavily, Dean stepped forward and set a cautious hand on his friend's shoulder. He felt Cas tense, but didn't pull back. "It's not gonna happen, Cas. We'll figure this out, okay? This Men of Letters bunker… their archives are crazy. With their info, the three of us together can figure out how to get that program out of your head. Alright?"

Cas twisted, just enough for Dean to see a hesitation of hope in the angel's anxious eyes.

The building door slammed; both of them turned to see Sam wiping the angel blade clean.

"He didn't know how to un-program Cas. Said only Naomi knew," Sam reported, then he shrugged. "He won't be a problem anymore." He held the blade out to Cas, who stared at it for a second before reaching hesitantly for the weapon to tuck away once more.

"Great," Dean muttered. "Well, at least we know the code to turn it off, just in case anyone tries something. Cas, we're gonna fix this." He raised his eyebrows. "Trust me?"

"…I trust you."

"Good." It was all he could do to put on a reassuring smile when his insides were still boiling with anger and worry, but Dean clapped a hand to Cas's shoulder again and nodded towards the Impala.

He was going to free Cas from Naomi, once and for all. No matter what it took or who he had to go through. Because nobody messed with Dean's family and lived.