Warning: Possible spoilers up through Season 5's Abandon All Hope.

A/N: For my Dean/Jo 'shippers, especially Silverspoon and WelshWitch1011, who've been itching for me to do a multichapter fic. Sam, Tori - This one's for you. Y'all really need to learn to be careful what you wish for.

As a housekeeping matter, I'll be tying in bits from my If Only For Tonight...and Can't Fight This Feeling. It's not important that you've read those, but it may help as I am going to be veering away from cannon.

Many thanks to stephaniew for her friendship, betaing and willingness to take this idea through. I might have shelved this idea without her encouragement and help jumping over the hurdles my muse tried to throw at me. Check out her stories and see how, like Jo, her OC keeps Dean on his toes.

Disclaimer: I don't own Supernatural.

Prologue: The Butterfly Effect

The idea that something as simple as the flutter of a butterfly's wings could change history was originally brought to light by Ray Bradbury in his short story A Sound of Thunder. It wasn't until almost a decade later that the term "butterfly effect" was popularized by meteorologist Edward Lorenz, who claimed that the flapping of wings could alter the course or pattern of weather. Though the consequences and locations of occurrences have changed as the theory has made its way through different circles, one thing has remained constant - the image of wings setting something in motion that ripples across time.

Everything happens for a reason. It may be for good. It may be for bad. The point is it happens. Call it fate, luck, providence; call it whatever the hell you want - it's something different to everyone. Whether it's a spilled cup of coffee that makes you run five minutes late or being born into a family of hunters, tiny little details can have a serious impact on your life.

Every story has a beginning, a middle and an end. There's plenty of story before where we pick up this tale and there'll be plenty more to come long after it's done. Because life - love - is the greatest story of all.

This story begins in 1985. Back to the Future was the top grossing movie in the US and compact discs were introduced to American consumers. REO Speedwagon's Can't Fight This Feeling was the number one song for the month of March and number twelve for the year on Billboard's Top 100.

More importantly, on Sunday, April 7, in small town Nebraska, hunters William and Ellen Harvelle welcomed their only child - a daughter - into the world. Truly her mama's baby girl, Joanna Beth was a bit of a tom boy. Far from typical, she was never much for the color pink or fairy tales. When your parents are hunters, you become all too familiar with things that go bump in the night. You learn all too early that stories and fables never get the monsters quite right. And then there's the most devastating lesson of all - there are no happy endings.

Harvelle, a surname meaning woman warrior. And that was what she would become. Standing a mere 5'4" tall, she was no Amazon but she was tougher than iron nails. Though pretty, she was far from classically beautiful. She had dark, wide-set eyes and honey-blonde hair that curled softly down her back.

She was more denim than lace, hustling pool as soon as she could see over the table and learning everything she could from the hunters who frequented the family's Roadhouse. She had Bill's penchant for getting into trouble and Ellen's stubborn streak. She'd shoot guns as quickly as she'd shoot off her mouth.

The day Jo Harvelle first laid eyes on Dean Winchester, she'd pressed a shotgun into his back and punched him in the mouth before introductions were made. Jo was nobody's fool. She didn't believe in heroes in shining armor riding in on white horses. She believed in independence and, having been raised by a strong-willed woman, believed that men and women should be equals.

Tales of the Winchester family were legendary. She found herself drawn to Dean despite his reputation. He wasn't a knight in shining armor, nor did he ride into her life on a white steed. He was flawed and rough around the edges, tarnished beyond repair. And his horse? Try the power of 275 of them roaring beneath the hood of his black 1967 Chevy Impala.

He wasn't the kind of man she was used to. They'd bickered and flirted. He'd flashed her a devilish smile - or six - that hadn't quite reached far enough to cover the sadness housed in his sparkling green eyes. But, at the end of the day, he hadn't tried to get into her pants with a six pack of cheap beer and side one of Zeppelin IV. Instead, he'd just smiled and said "wrong place, wrong time."

For a while they did more falling out than falling together. Emotions ran high at the discovery that Dean's father may have contributed to the death of her own. But it was his guilt over his brother's treatment of Jo while possessed by a demon that seemed to drive them apart completely. That and his desire to somehow right his father's wrong against the Harvelle family by not leading Jo into the path of destruction that plagued the Winchester name.

Several years would pass before they'd meet again. The Roadhouse burned to the ground, taking the life of her friend Ash with it. Dean died and was resurrected by the angel Castiel. Against her mother's wishes, Jo started hunting on her own. Back from Hell, Dean was made to confront his inner demons and the torment of what he was forced to do while in the pit.

When they join forces again, it's in the face of the impending apocalypse. Dean and Sam were running down the four horsemen and collecting their rings. Jo and Ellen joined the brothers in their quest and, together, the four would face demon possession and go up against War.

After breaking the horseman's spell over them, it's not until a chilly night in November that Jo squares off with Dean again. It's the night before Death will be summoned to earth. The night before Dean and Sam will face off with the devil himself.

The buzz of alcohol humming in the air between them, they'd stand inches apart as he used a line that he'd used on other women. A line that had worked so many times before. One that, to this day, he's not sure why he allowed to pass his lips in her direction.

She'd laughed and asked if he was giving her the end of the world speech. The girl in her - the one that's had a crush on Dean almost from the moment they met - is ready to give up her panties, surrendering to his charm. The woman in her - the one who's stubborn as the day is long and refused to settle - is the one that turns him down.

And that's where the butterfly comes into play. Unable to sleep, Jo made a choice. It was a choice that had long term ramifications, setting in motion an unforeseen series of events. It wasn't fated to happen that way - they were never meant to be together - but a silk-spun thread, one softer than the angel's feather it was woven from - snagged. Joanna Beth did something no one saw coming. She exercised free-will in a moment when those watching over her were temporarily blinded.

You see, like any good warrior, she had strength. She had strength and the courage to take risks. Having the courage to stand up and fight for something you want is never a mistake. Taking a different path, turning a door knob - like the wings of a butterfly, or, perhaps, an angel - could change history.

The night Jo Harvelle crept from her bed and melted into Dean Winchester's arms - the night before her death - changed her fate and the fates of those around her. And if you truly believe that Joanna Beth Harvelle's story ended with her life at the claws of a hellhound in Carthage, Missouri, you'd be wrong. Her purpose was - is - far greater than that.