"This is a dictatorship."

Since discovering the tribal-looking brand on his brother's forearm, Sam had been noticing things. At first, it just seemed like Dean being Dean. Drinking too much. Not sleeping for days. Overzealous in hunts. Nothing particularly memorable. That is until the Thinman job. Sam had looked up and watched, uncertain whether or not to intervene as Dean slowly, coldly stabbed Roger through the heart with his own knife. The determination to make it a slow, painful death stopped Sam in his tracks. Something was off here. Dean had always been a little quicker to kill than he was but a human?

Human monsters were for the police, and any person other than Sam might've called them on Dean for that malicious display.

From that point, Sam kept a more careful eye on Dean. He'd looked up the Mark of Cain before but hadn't found much other than the old testament story of Cain and Abel which was now even less comforting, given Dean's quick trigger attitude as of late.

The first time Dean held the Blade, Sam felt something he'd never felt around Dean before. Afraid. Dean wasn't himself. Or at least, Sam told himself that, whether or not Dean wanted to be this dead-eyed, bloodlusty thing he was becoming was never discussed. But Sam remembered watching Dean. That glassy eyed stare that traced the bloodstained crevices of the Blade and how he almost looked like he was getting high off the sweet, coppery stench of a clean decapitation. He turned his gaze on Crowley, whether he wanted to kill him or thank him- who could know?

But as Sam practically begged him to drop the fucking Blade, he did it. The desperation, the fear in Sam's voice was what seemed to break through.

In the week that followed, Dean came down off that disturbing, homicidal high and he was just agitated. Jittery, too wired, too awake. All the time. Strung out beyond all belief. But Sam wasn't going to question it, or even help, if he'd known how, Dean got obsessive sometimes. Though never like this.

And then there had been the great 'interrogation' of Gadreel. Meaning, if his vessel had still been alive, it wasn't once Dean was done with it.

And then that nest of vampires.

"Look at me..." Sam, barely conscious at the time felt his stomach tense up at the inhuman request his brother had just made, machete pressed up against the vamp's throat, "Look at me, bitch!"

Not content until the thing made eye contact, Dean had pushed the blunt end into it's neck, severing it, watching with a sick satisfaction as the life left it's eyes.

But nothing, nothing, was more terrifying than the execution of Abaddon.

Sam had slipped into the room, ready to find Dean fighting for his life considering he'd sent his only backup on a wild goose hunt in the basement. But instead he found Dean stabbing that Blade through the Knight of Hell who died in a bright explosion of light. And that should've been it. But it wasn't.

As her lifeless form collapsed, Dean went down with her. Raising the Blade above his head, he stabbed her again. And again. And again and again, blood splattering all over him, teeth clenched, lip twitching.

"Dean?"

He wouldn't stop. He just kept stabbing the meatsuit, over and over, mutilating the poor, dead vessel.

"DEAN! STOP!"

The effort it looked like it took to stop himself was certainly something to be worried about. He had finally stopped, looked up from his bloody masterpiece to his brother, staring at him like he was a monster. Because he kind of was.

"You can stop."

He'd let the Blade fall from his hand, and he seemed to retreat into himself. And as Crowley bitched and complained as he dug the bullet out of his chest, Dean disappeared to rinse the blood off his face, and Sam kept his distance to allow him to compose himself. Get control. Come down.

But here he was now, telling Sam, they're not a team. This is a dictatorship. Dean, and Dean alone has the Mark and can use the Blade and can end Metatron. And Dean will kill him.

The rush Dean got off murder nearly made Sam sick a few times.

As he headed for his bedroom to try and sort his thoughts. Find some way to reach his too far gone brother, he caught sight of an intruder. Gadreel.

"Guys!" He'd yelled, turning back, warning Dean and Cas who turned, ready to fight.

"I'm not here to fight." Gadreel said, holding up his hands in surrender, "I thought about what you said. You're right. Metatron, he's...something needs to be done ."

Sam could see something honest in the angel's eyes but he wasn't about to trust Kevin's killer and his captor so easily.

"And we should trust you, why?"

"Because I can give him to you. I know where Metatron is. I know everything. I know the bombers. They were his agents, not yours." Gadreel looked around, felt the rejection of his surrender all around him and said, "You don't trust me, fine. I understand. I've...made mistakes. But haven't you?"

He looked around at Sam, at Dean, at Cas, desperate. Desperate for redemption.

"Haven't we all? At least give me a chance."

Sam felt a strange sense of pity for the angel. Of course he knew the feeling. The three of them had screwed up themselves, each other, and the world more times than anyone else he knew. Dean extended a hand. Thank god, he was showing at least that much empathy. To understand that everyone makes mistakes, everyone deserves a second chance-

FUCK.

In one quick movement, Dean had pulled out the First Blade and slashed open Gadreel's chest. Blood and Grace poured out as he collapsed and Dean lunged forward to finish him, but Sam was quicker.

He grabbed Dean, holding him back as he snarled.

My brother's rabid, Sam thought, glad Castiel was there to help. Sam wasn't sure he would've been able to keep this feral Dean under control himself.

But the two of them weren't enough. Dean wrenched free, Sam spread his arms out, blocking his killer brother from causing the fallen angel any further harm.

"Sam, move." Dean growled in the least Dean way Sam could've imagined.

"Dean-"

"SAM. MOVE." Dean said louder.

And in that moment, Sam wasn't afraid for Dean. He was afraid of Dean.