When Roy fired, when his brother was killed, Dean's mind went blank.
He couldn't think anymore, because his brother, his little brother – Sammy... Sammy was dead. And this time, he wasn't able to save him. He couldn't make a deal, and being thrown back in Hell, the angels wouldn't allow it. Not when they needed him.
That's when the solution hit him.
CAS! he yelled in his mind, hoping the dark-haired angel could hear him. Cas, please! Sammy's dead, I need you, please!
Barely one second later, the angel was there, just behind the two other hunters, who were still debating if they should kill Dean too or not.
“What happened?” Cas asked, eyes fixed on Dean.
Roy and Walt jumped, turning on their heels and pointing their guns on Castiel, who didn't acknowledge them, entirely focused on the oldest Winchester.
“They killed him.” Dean said. “Because they discovered he was responsible for the Apocalypse.”
Cas, who hadn't even look at the other two guys, froze. His face became blank, and his posture way more angel-ish. He stared at the two hunters, not at all concerned by their gun.
He walked past them, stopping next to Sam. He lifted two fingers, positioning them on Sam’s forehead. The youngest Winchester took a deep breath, brought back to life.
“What the hell – ” Walt started, but Cas interrupted him. “Sam Winchester is under my protection. If you threaten him again, I will show you no mercy.”
“Who the hell are you?” Roy snapped.
“I'm an Angel of the Lord.” Cas answered, voice deep and cold. “And I am warning you again: if you hurt the Winchesters a second time – or if you asked some of your friends to do it for you – I will kill you.”
And then, so fast Dean eyes had difficulties to catch it, he moved, posing two fingers on the two douchebags' forehead, sending them away. When they were gone, he turned his head toward Sam, worry in his eyes.
“Are you ok, Sammy?” he asked.
“Well, I'm pretty sure I died.” said the long-haired man. “But you apparently brought me back, so thanks. I know you don't really like me, Cas, so –”
“I was unfair to you.” Cas interrupted him. “In the beginning, the fact that you have demon's blood made me wary. And I am sorry for that. But, we... We are friend, now, aren't we?”
“Of course we are.” Sam smiled.
“Plus, you are Dean's brother.” the angel added. “I couldn't let you die.”
“Thanks, Cas.” Dean said after a few seconds.
When their eyes locked, Sam smiled a little more, and the other two were completely oblivious to it, concentrated on each other.
There was something between his brother and the Angel. Sam didn't know what exactly, but it was there. A possibility.