Cause and Effect

Summary: Their timelines cross and diverge and cross again, their fates bound up together and entwined with the Doctor's. River, Rose, and their interlinked destinies. Oneshot.

Author's note: Written for miranda_wave for the dwsanta Holiday Fic Exchange on LJ. Special thanks to jessicaqueen for being awesome and beta'ing this for me.

Disclaimer: Don't own it; don't sue me.

London, 2005

"Mels, where did you get that?" Amy hissed, scandalised.

Mels noted in amusement that Amy was looking around Henrik's nervously, as if a security guard was about to pop out of nowhere and haul them both off. For all her bluster and bravado, she really was such a good girl. There was nobody nearby except for a blonde shop assistant who was folding clothes with a glazed-over, bored expression on her face.

"Oh, will you just relax?" Mels wrenched her wrist from the other girl's grasp, swinging the small plastic bag of money carelessly back and forth. "It's not even that much, only a few quid."

"This is supposed to be a holiday, Mels. We're here to shop, not steal!"

"Stealing?" Rory had finally caught up to them, laden down with bags full of the girls' purchases. His anxious gaze darted from Mels, to Amy, then back to Mels. "Who's stealing? Are you stealing? Mels, you better not be stealing…"

"It was hardly stealing," she retorted, rolling her eyes. "I mean, it was just lying there, right out in the open."

"Right out in the open?" Amy folded her arms, one eyebrow arched in scepticism.

Mels grinned. "Okay – in a drawer, behind the cash register." She was met with horrified glares from both teenagers. "What?"

Amy took a painfully tight hold of her upper arm and began marching her towards the doors. "You are going to give that money to the security guard," she told her firmly as a voice announced that The store will be closing in five minutes, thank you, "and then we're going back to Rory's aunt's place. No detours, and nothing else illegal."

Mels pouted. "Oh come on, Amy. Can't a girl have a bit of fun?"

"Not this kind of fun," Rory put in from behind them.

Amy deposited Mels a little way away from the security guard and stood next to Rory just outside the doors, both of them watching her like hawks. Mels sighed, straightened her shoulders, and plastered an innocent smile on her face.

It only took a few seconds to convince the guard that she'd found the lottery money lying on the floor near the cash registers. She was awfully good at lying, after all.

"Not many people would be this honest," he said with a grateful nod.

Mels glanced over at Rory and Amy, and smiled. "Well, sir, it's how my parents are raising me."

She darted off to join them, leaving the bag marked 'Lottery' in the guard's hands.

Gamma Forest, 5106

"One of the safest places in the universe," the Doctor had said as he dashed about the console, the TARDIS lurching urgently through the Vortex. "The Gamma Forest, home of the Sisters of the Infinite Schism. It's the perfect place to lie low. Neutral in every conflict, like Switzerland. You like Switzerland, don't you? Everyone likes Switzerland. Clocks, cheese, chocolate!"

Of course, when they're being chased across time and space by some kind of huge android space vampire intent on consuming the energy of the TARDIS (and anything else that might be in the way), even the universal equivalent of Switzerland isn't safe. And Rose hasn't seen any clocks, cheese or chocolate so far – just trees and the winding river, and all of that has been nothing but a blur as she's run past.

She's been separated from the Doctor; his last instructions were to get to the hospital and alert the Sisters while he did… something (she thinks he rattles off the rapid jargon-filled explanations to show off, anyhow, not because he thinks she understands). The trees are thinning and she knows she's close – the vast hospital with its glowing green crescent rises above the canopy, bright and modern and white, a strange contrast to the surrounding forest.

The doors slide smoothly apart to let her through and she pauses just inside, out of breath. One quick glance around tells her that hospitals aren't that different in the fifty-second century, and she races up to what she figures must be the reception desk.

It takes far too long, frustratingly long, to make herself understood to the young nurse on duty, and she knows that she looks a little bit crazy with her wild eyes and inflexible demands that the nurse summon every available member of staff.

Rose is almost relieved when an explosion from somewhere outside rocks the very ground beneath them, lending a little more support to her rushed, incomplete explanations. The nurse's eyes widen to saucers and she hurriedly hits a button and speaks in a forcibly-calm voice over the intercom, requesting the urgent attention of all Sisters on duty.

"Rose!"

She spins around and her frustration falls away at the sight of the Doctor, running into the hospital. Rushing over to him, her smile falters slightly when she sees that he's holding the hand of a frightened little girl.

"Who's your friend?" Rose asks him, nodding to the girl, who's practically wheezing from what must have been quite a run.

"Rose, Lorna. Lorna, Rose," the Doctor introduces them quickly with the bright smile that Rose often finds inappropriately charming, considering the dangerous situations they're always in.

"Hi, Lorna." Rose bends down slightly and gives her a little wave and what she hopes is a reassuring smile. Lorna says nothing, just stares back at her with wide eyes.

Pleasantries over, the Doctor is now focused on the task at hand. "Rose, did you-"

"Already taken care of, Doctor." As she speaks, nurses run in from all directions as another explosion shakes the floor.

The Doctor grins and holds out his other hand to her. She takes it without hesitation. "Ready?"

Rose grins back. "Ready."

Luna University, 5124

Even after her decision to build her own identity from scratch, to strike out on her own and discover what it meant to be River Song, she was never completely sure that her desire to find the Doctor was wholly her own, or a by-product of a lifetime of conditioning.

She eventually decided that it didn't matter why she wanted to find him. What mattered was what she wanted to find him for. She decided to use the university's resources to research the Doctor's many incarnations throughout history, not because she wanted to hunt him down and kill him, but because she simply wanted to know him and discover all she could about this wonderful, impossible man.

She used what she knew of him to guide her search: his affection for the human race, his love of danger, his inability to resist observing – and intervening in – the significant moments in history. But he was a mysterious figure in anyone's language, and she often came up against dead ends.

Yet she began to notice a faint pattern, something else that was woven into history with the Doctor: two words that were sprinkled across time and space, another, more subtle, companion. Time after time, she would skim over those words, and a few hours of record-digging later, she would find a mention of the Doctor or an image of one of his faces.

The discovery renewed her determination to learn all she could about him. And now she had a lead: find the Bad Wolf – find the Doctor.

Stormcage Facility, 5098

The twenty-second shift deposits Rose in a dark, cold room full of weapons and armour. They haven't yet refined their technology to lock onto a particular point in the Doctor's timestream, but they have managed to get a lock onto the TARDIS. She's been sent to something called the Stormcage Facility, a place the TARDIS apparently has been frequenting in the 51st century.

She's watchful as she exits the room and walks along a winding corridor, every muscle tensed, on alert for any sign of trouble, any sign of the Doctor. The universe is huge and timelines are complex, and so even though this is the best lead they've ever had, she knows she shouldn't place too much stock in it. Yet there's a thumping in her heart that she can't control, a feeling of anticipation that can't be helped.

Armed guards are stationed at various points along her path, but all those journeys with the Doctor and all her journeys since have taught her a thing or two about stealth and distraction and opportune moments. She manages to slip past unnoticed, her exploration largely unhindered.

After some time, she approaches a corner and her shadow stretches on beyond it. A creaking, squeaky noise and another set of footsteps echo back to her, and she freezes as a confident, cheeky, female voice calls out.

"Half an hour early for dinner! Have I been a good girl? Am I getting a treat?"

Brow furrowed in confusion, Rose cautiously rounds the corner, hand hovering over the gun holstered at her hip that her mother and Mickey had insisted she carry.

She stops short when she sees the owner of the voice: a curly-haired older woman, holding onto the bars of what must be a prison cell, looking back at her with blank surprise.

"Well," the woman says, placing a hand on her hip. "I'm guessing you aren't the new guard. Or if you are, they must have misread my memo." She looks Rose up and down, a small smirk playing about her lips. "They got the 'blonde' bit right, though."

Rose eyes her warily, but some instinct tells her not to lie. "I'm just… passin' through."

The woman cocks an eyebrow. "Not a lot of people just 'pass through' Stormcage – unless they're wearing a uniform. Or handcuffs – and you don't look like you'd want to share mine." She draws closer to the bars and peers out at Rose. "I do like the tight-pants-and-purple-leather combo, though. Must remember to suggest that one to the boys."

Rose ignores her and looks around, trying desperately to find a sign, some confirmation of the Doctor's presence. She knows she's in the right place, or at least she's come out in the location where they intended her to come out, but why would the Doctor be coming here, to what must be a prison? Who is this woman? Does she know him? Whether she is friend or foe doesn't matter to Rose. She just needs to find out where he is.

That's when her gaze alights on the book lying on the woman's cot – that bluest of blues, the unmistakable design.

Eyes wide, heart pounding in her ears, she asks sharply, "Where'd you get that book? What is it?"

The woman turns, following her gaze, and pauses a moment before waving a hand dismissively, evasively. "Oh, that. It's just… a gift from a friend. Prison, you know – hard work getting good entertainment if you don't write it yourself."

Rose narrows her eyes. "This… friend. Does he…" She falters. If she asks, if she says his name outright, and this isn't the parallel she's looking for, will she change the causal nexus? After crossing so many parallels, after seeing and doing so much, she's learned now that most of the time the less she says, the better.

The woman has turned back and is watching her carefully, and Rose can't tell what she is thinking. She glances at the book again – it's definitely the same design as the TARDIS. She'd know it anywhere. And if this woman says she got it from a 'friend'… well, maybe it will be worth the risk. She just has to choose her words carefully.

Rose steps closer, gaze locking with the woman behind the bars. "Does your friend travel in a blue box?"

The woman blinks. "Blue box?" Her expression remains neutral, but Rose, staring into her eyes, thinks she sees some flicker of emotion in their depths. It's that flicker that prompts her to move forward, her own impassive expression cracking a little as she seizes onto this tiny shred of hope.

"If you know him," she says, her voice sounding strained under the weight of her sudden desperation. "If you've seen him – the man who travels in the blue box – I need to find him. I've got to find him."

The woman looks at her for a long, long moment, and something about her unfathomable gaze gives Rose the uncomfortable feeling that she is scrutinising her very thoughts. But her silence seems to confirm that she knows something.

"You know who I'm talkin' about, don't you?" Rose asks, searching her face for confirmation. "You've seen him. You've seen the Doctor."

Behind the bars, the woman's expression changes, and suddenly she's staring at Rose with something like recognition and wonder.

"You," she breathes, reaching up to hold onto the bars as she draws herself closer. "It's you, isn't it? The Bad Wolf."

Rose blinks and stares at her. "What'd you just say?"

The woman smiles: a wide, enigmatic smile. "It is you, isn't it? You're in the right universe, but you've come too far forward in his timeline."

"How'd you…?" Rose is thoroughly taken aback – who is this woman, and how does she know where she's come from?

"Trust me," the woman says simply. "Just go back further, and you'll find the Doctor."

Rose steps right up to the cell and searches her face. "Who are you? How d'you know all this?"

The woman shakes her head. "Sorry. I can't tell you. Spoilers."

"Spoilers? Wh-" Rose cuts off, and shakes her head. "Doesn't matter. You know the Doctor?"

"Yes."

"And you're sayin' if I stay in this universe – I'll find him?"

"Yes."

Rose narrows her eyes. "Why should I trust you?"

The woman shrugs. "You don't have to. But really, what do you have to lose?" She leans back and looks her up and down again, this time with a small, pensive smile on her face. "It doesn't matter, in the end. You're Rose Tyler. One way or another, you'll find him."

Rose stares at her. This woman knows the Doctor. She knows her name. She knows why she's here. And she's right, too – all Rose has to lose is a little more time, and if the Doctor isn't here, then she doesn't have many other leads she can follow.

Finally, she nods and pulls her phone from her pocket, watching the woman closely as she dials.

"Control? Shift me back home. I think I've got a new lead we need to follow up." She flips her phone closed and pockets it, stepping back from the cell. She considers the woman, pressing her lips together.

"Who are you? How d'you know him?" she demands suddenly, the words tumbling out quickly as she knows it will only be a few seconds before she is whisked back to her regular universe. "Tell me your name."

The woman continues to smile, with kind yet inscrutable eyes. "My name is River Song."

There's no time for anything else. The air around Rose begins to crackle, and the last words she hears before the dimension cannon pulls her back are: "You'll find him, Rose."

Satellite Five, 200100

All of time and space is laid out before her, and she sees everything. The Daleks: their creation, their cruelty, and their persistence, like a virus. Her Doctor: so many different faces, running so fast and so far across the universe. Herself: every choice she has ever made, every choice she will ever make. This is where she has always been headed, an inevitability to which she never realised she was bound.

She is limitless. In this moment, she exists everywhere at once, through all ages, omnipotent, benevolent. She is the end of the Time War. She is the destruction of the Daleks. She is the Doctor's saviour. She is the Bad Wolf.

She flings the words like stars across the universe, woven into the very fabric of time itself, signposts on a hundred different roads that all lead to the Doctor.

She sees so many timelines: her own, the Doctor's, a woman named River Song whom she knows she will meet one day. Their timelines cross and diverge and cross again, their fates bound up together and entwined with the Doctor's.

With the power of the Time Vortex burning through her mind, she knows that she is not the only one who follows the Bad Wolf to find him.

Gamma Forest, 5122

Her whole life had been about purpose, about finding the Doctor and doing what she had been trained to do from the moment she was born. Now that purpose had subsided (she'd done what they wanted, hadn't she? She'd killed the Doctor, sort of; she didn't particularly want to do it again) and she was left with questions. Who was she? What should she do with her life? All those years of honing her body and her mind to become the perfect killer – what could she do with those skills, those motivations?

The Sisters of the Infinite Schism insisted that she stay at the hospital in the Gamma Forest for another four months. Physically, she was mostly fine, though she found herself getting tired too quickly – apparently donating the rest of her lives to give him life had drained her almost dry. Mentally – well, that was another story altogether, wasn't it? Sometimes, she was glad for the opportunity to sort through the mess of her mind, throw out what wasn't really hers, and discover who she really was. Other times, she had to fight the urge to steal a scalpel and escape to find the Doctor – whether to kiss him or kill him again, she wasn't always sure.

She slowly learnt to control her own mind with the help of the Sister who had been assigned as her nurse and psychotherapist. Sister Andry was a calm, sharp, middle-aged woman who had been born and raised in the Gamma Forest. When Melody grew bored and restless, tired of therapy, tired of sifting through her memories, tired of talking about her ridiculously complicated feelings for the Doctor, Sister Andry was patient. She began teaching her ward her native tongue and taking her for the occasional walk through nearby segments of the Forest, telling her stories of her tranquil life among the trees.

Melody liked the idea of a peaceful life, the stories of the kind of youth she had never experienced. She listened hungrily as Sister Andry recounted childhood antics with her brothers, culinary lessons from her mother, her indoctrination and training with the Sisters of the Infinite Schism. Yet the one story that Melody asked her nurse to re-tell over and over again was not one of peace, but of disruption, destruction, salvation.

"I had only begun working here a few months ago," Sister Andry would begin with a faint smile. "And I was at the reception desk. All of a sudden, a young woman came rushing up to me, wild-eyed, talking so fast I could hardly understand her. She kept ordering me to alert the other Sisters, to tell them that something bad was coming this way and that it would destroy the whole hospital if we didn't prepare. I didn't believe her, of course. But then there was an enormous crash, and the whole hospital shook."

"And then a man came running in," Melody would continue for her, the words now as familiar to her as if she had lived through it herself. "The woman's friend, a mighty warrior – a Doctor. And the two of them saved the hospital."

Something about Sister Andry's story made her wistful, and it was not, surprisingly, because it involved the heroics of the Doctor. After all, she had grown up hearing those kinds of stories from her mother, tales of monsters and running and a man who swooped in to save the day with a screwdriver and a lot of words. What broke through the surface of her obsession with the Doctor was Sister Andry's description of the woman who had accompanied him. She was strong, independent, resourceful. She was a woman who would do what needed to be done. She cared about people. She was a woman who the Doctor could count on.

With her identity in flux and her life ahead of her, Melody could do anything or be anything. But what she wanted to be was a woman like the one from Sister Andry's story. Melody had caught a glimpse of her future through the Doctor's eyes, and she knew that one day she would become that kind of woman. But she wasn't there yet.

When they finally discharged her from the hospital, she was ready to go. She was ready to stride across the stars and recreate herself, mould herself into the woman she wanted to be.

"Thank you. For everything," Melody murmured, hugging her nurse and friend.

"You're welcome," Sister Andry replied warmly. She said her farewell in her native language. "Goodbye, River Song."

Melody walked away, and smiled as she boarded the transport that would take her away from the Gamma Forest and out to the stars – next stop, anywhere. The name swirled through her thoughts. River Song.

This was the day she would become River Song, she decided. And the next time she found the Doctor, she would be the River Song he knew.

London, 2005

"Wilson? Wilson, I've got the lottery money. Wilson? You there? Look, I can't hang about 'cause they're closin' the shop…"

It happens like dominoes falling: she's trapped in the basement of Henrik's; plastic mannequins come to life; and a strange man in a leather jacket takes her hand and tells her, "Run!"

Later, years later, lying in bed next to her Doctor and listening to the steady beating of his single heart, she will think back and mentally trace the paths that brought them together. She will think about all the what ifs: what if she hadn't left with him? What if he hadn't followed the plastic arm to her house? What if Mark hadn't handed her that bag of lottery money in the first place?

There is no need to consider the alternatives. Because right now, in this moment, running hand-in-hand with the Doctor for the very first time: this is the day when Rose's life begins.

Fin