I did not create The Big Evil Mommy/Jess Killer Fire Demon, Johnny, dear Mary, darling Dean, Sammy-boy, or his sweet Jessica. Eric Kripke has that feather in his cap.
There are spoilers only for the entire season, and then an AU for "Devil's Trap."
All mortals tend to turn into the thing they are pretending to be. – CS Lewis
Sam Winchester was a mighty fine actor. He was clever and strong and never took off his mask, not for anything.
For four years he played the part of 'normal': a younger son who had escaped the family business and gotten into college. And the only thing he told his friends about his parents was that his mother died and his father didn't approve of schooling.
He didn't mention Dean at all, except once in passing to Jessica. She asked but he never answered.
He went to class, kept two jobs, dated Jessica, lived his life drenched in normalcy. No one knew what he hid in the past shrouded by darkness; it existed only in his blood-soaked dreams.
And then, of course, Sam's past came crashing down on his future and Jessica died, anointing Sam with her blood.
Sam played another part; instead of the college student, he became the vengeful hunter, the same act as his father. Dean saw through it, of course—he always had. But he didn't speak of it, never had. He let Sam keep hold of his illusions.
And then they found Dad—or rather, he found them, twice—and everything happened—Meg and The Demon possessing Dad, and Sam having to choose, and Dean—Dean being broken in front of his eyes, Sam helpless…
And his telekinesis clearly didn't get the memo, because Dean was dying, Sam could feel it. The rage and pain welled up; he could feel them, swirling around him, but the gun refused to move and Dean was dying—
Dad… don't let it kill me…
And Sam was free, the gun in his hand and his father shot through the skull.
Sam didn't pause, just lunged forward catching Dean as he collapsed, cradling his brother's bleeding form.
"Sammy…" Dean whispered, hazel eyes flickering, "Dad'll be alright, right?"
Sam nodded and answered, voice thick with tears, "Dad'll be fine, Dean." He ran his fingers through Dean's hair, not even trying to hold in the tears, and Dean just kept bleeding.
Sam grabbed Dad's coat and tried to put pressure on the wounds but Dean said, "Don't. Just…" he coughed blood, "let me go, Sammy."
"Would you sit and watch me die? Dean, huh, would you sit and watch me die!" Sam knew his voice danced on the edge of madness, but he didn't care. He couldn't lose Dean, not after everything—he wouldn't.
Dean's breath rattled and Sam knew the time had come.
"Do you know where Dad got that necklace?" he asked, lightly, touching it as Dean took his final breaths. "We went together to pick it out for you—one of the few times we got along." Tears poured down his face and Dean's chest stilled. Sam glanced quickly at his father's corpse and said, "Dean, you promised to never leave me," touching the gold amulet.
And nothing happened.
Sam bowed his head and totally snapped. He sobbed and screamed and shook Dean's corpse and demanded Dean wake up and nothing happened.
He'd failed. Dad'd failed. The charm'd failed.
And Dean… Dean paid the price. Dean always paid the price.
Sam finally calmed and slept, never releasing his brother's body. His dreams held blood and death and Dean apologizing and cursing and falling and breaking—
And Sam woke at dawn, Dean held in his arms and the colt—one bullet left—within reach.
He'd failed. Dad'd failed. And Dean's charm, his protection, the final hope… Sam kissed Dean's hair and grabbed for the gun, Dad's corpse glaring at him.
"You promised to never leave me," he whispered. "You swore it." Tracing the edges of the colt, he wondered, "Did that fight—you remember, when I met Meg and had to save your ass?—you left me. Did that negate the charm?"
With one last look at Dad, Sam raised the gun.
He'd learned that bullets traveled quicker than sound, so you'd never hear the shot that killed you. With Dean spread out over his lap, he wondered if it were true, because he pulled the trigger and—