On The Flip Side

Chapter 1

((Cross Posted on AO3 anonymously!))

In one world, the apocalypse starts. John Winchester loses his sons and his mind with them. He picks up a baseball bat, he wraps it in barbed wire, and he releases his grief with every swing he takes.

On another plane of existence, the dead don't rise, and John is the one who dies. His sons mourn him. They keep him in their memory and try to do right by him, because even if he wasn't the best father, they both know he tried. And they figure that's a hell of a lot better than nothing.

The theory of alternate dimensions is a curious one. Parallel universes in which the slightest change causes them to branch off into their own, respective paths. It's a complex concept to play around with, one most won't touch with a ten foot pole. Too many 'what ifs', too many hypotheses that are impossible to test or prove.

Still, Sam really, really wished he read up on the speculations and little known research. Even just skimmed it.

"I'm sorry." Dean says, voice flat and barely audible over the groans of the dead outside. They ram into the car, rocking it precariously from side the side. "What the hell is this?"

"An alternate dimension." Cas answers patiently from the back seat. It's the fourth time he's said it and it's still settling in. "I'm afraid we have driven through a rip in the universe. Here, an apocalypse in which the dead have risen has wreaked havoc on the Earth. I believe society as you know it has likely collapsed."

Right. Naturally. Such an obvious answer, they really should've just been able to guess.

"Yeah, no, we get that. Zombies. Other world. That's great." Sam agreed, nodding and trying to take it in stride. The smell was agonizingly putrid and nearly overwhelming, even with the barrier the walls and windows of the Impala provided. "You just haven't said how we managed to do that. Drive through a rip in the universe, I mean."

How do universes even rip? Is that a thing? Sam guesses it pretty clearly is, seeing as he blinked and suddenly they're in the middle of a massive hoard of literal zombies. Which definitely hadn't been there before. Sam would've noticed, he likes to think.

"Can I reverse us back through it?" Dean asked hopefully, looking at the gear shift with a gleam of contemplation in his eyes. Cas blinked in that slow way he always did when he thought they were being morons but was too nice to say it.

Sam's not sure how their luck is this bad. No, really— they hadn't even been doing anything this time. Coasting down the road, listening to music. A job well done in the bowels of Virginia had left them feeling satisfied and content. They'd planned to head to DC just for the cuisine since it was so close, and lo and behold. Suddenly they're surrounded.

"Unfortunately, the rip will have closed by now, repaired by the natural balances." Cas said it simply, like they weren't about to get eaten alive by the undead. Thank God Dean had splurged on reinforced windows after the last time they got broken. "We are stuck here. Such an event is... rare. Less than a .00001 in centillion chance, though clearly not impossible."

"Great. He's using numbers I don't recognize." Dean mourns, dragging his hands down his face.

Sam feels a headache start to form. He can't tell if it's from the smell or if it's from Dean's general stupidity. Maybe both.

"So what? We're just stuck in the end of the world now?" Sam asks. Cas gives him the 'you're a fucking idiot' blink again. "Why are you so calm about this?!"

"These things happen." Is all Cas says which... alright. Sure.

Dean seems to come to the executive decision that sitting here waiting for his car to get cracked open like a pinata is probably not the best idea. So he takes his foot off the brake, cracks his neck, and eases back onto the gas. Sam's honestly surprised he didn't just try to gun it. The whole situation feels claustrophobic.