(This story is for 332249, who had the idea but wanted me to write it. Set at the end of the last episode of season one, some of the dialogue is directly copied from that episode. This is not a full alternate universe story, just a scenario that could lead to a completely differently story line.)
Sam stared down the barrel of the gun at his father's face, twisted in pain and desperate hope.
"Son, I'm begging you. We can end this here and now. Sammy! You do this."
Behind him, Dean's voice was rough with pain but just as loud in Sam's ears.
"Sam, don't you do it. No, Sam."
Nothing was more important than killing the demon that had started all this. The demon who had killed Jess, killed his mother, taken away any chance at a safe, normal life.
Sam's finger hesitated on the trigger, Dean's plea ringing in his ears. He'd learned so much from his brother this year, learned to hunt again, learned to laugh again after Jess' death. He had discovered that he wanted forgive his father and be with his family, no more silence as they led separate lives.
A familiar pain stabbed through his skull and he staggered. Images flashed in front of his eyes. A vision? Now? But this was not scenes of far away strangers. This was different. It was how own future, his own face staring at him, pale with death lying on a filthy mattress. Then Dean, kissing a red-eyed demon at a crossroads.
What is this? Sam stared, unable to close his eyes against the horrors that flashed through his mind.
He saw Dean, his body ripped to pieces, lying in a hole while Sam covered him with dirt. Then he saw his own face, covered with blood, and felt the intense thirst as he licked his lips for more. There was static, like an old VCR on fast-forward, and then he saw Dean again. This time he was slumped against the Impala, face bloody, staring at Sam as if the world were about to end. A gaping black whole spread in front of Sam, and he jumped in.
There was darkness, and fire, and then Sam stared down another gun and saw his own hand killing monsters and innocents with the same bullet.
More images, a jumble of unfamiliar faces, wings, black ooze, a dog.
Then he saw Dean holding a blade that looked like bone, full of teeth, his eyes black. He saw himself holding a book, and then black smoke pouring from the sky and the earth. A woman in black, arms outstretched, ripped the earth to shreds. Sam saw the world dissolve as he clung to his brother and then there was nothing.
His vision cleared. Sam blinked. He was back in the shack, staring down the gun barrel at his father's face, Dean's voice ringing in his ears.
"No Sam, no."
Sam tried to clear the vision from his head. He didn't know what half of it meant, but there was no mistaking the end. He had seen the world dissolve. All because he put family first.
He glanced at Dean, lying in a pool of blood on the floor, tears streaking his face. Dean would fight for family first, always, even if it meant letting the demon go. Even if he could see the road ahead, he wouldn't care. He would let evil walk free and watch the world burn to save his family.
Sam had always looked up to his big brother, but he had never been like Dean. He steadied the barrel of the gun.
John's entire body twitched as he fought to maintain control, to keep the demon inside himself. "Do it, son."
"No, Sam!" Dean's voice was softer, distant.
"I love you, Dad."
Sam pulled the trigger.