An: Initially, I wanted to keep this as a self-contained ff. Too bad I'm terrible at keeping promises (especially to myself) and caved into exploring the theories of multiple universes and doppelgangers etc. With the show ending this week, I think this story is sort of appropriate. Be wary of that fact that these versions of Chuck and Sarah, while eerily similar to those we know so well, aren't exact. There are differences, but subtle and outrageous. Same with the rest of the characters from the fandom.

This ff shouldn't be *that* long. I have a general idea of what the overarching plot will consist of, and if you know anything about Donnie Darko (which I know a lot of my reviews do) then you can start piecing together what may occur. Though, I did take liberties and not the entire premise will reflect the beliefs in the movie.

I'd like to thank Aerox as always for helping me with this story: the French, and theories about quantum physics. Also, if you are remotely invested in this ff, I suggest you Story Alert it, since I know this was originally supposed to be a one-shot.

Without further ado.

Enjoy!

Chapter Two

The Butterfly Effect

They are inseparable.

It's been almost a month since their reunion at the beach, and the two lovers have wasted no time reintroducing themselves back into each other's very different lives.

They find their relationship is progressing fairly quickly. Much faster than the average couple. Their closeness and intimacy raises a few eyebrows, mostly by family and friends. However none of this comes as much of a surprise to Chuck and Sarah. For all intents and purposes, they are picking up where they left off. Married but without the rings to prove it.

Things have changed as well. Those reoccurring dreams have ceased; memories derived from their joint subconscious are fleeting. They can still remember bits and pieces. The sense of déjà vu remains stronger than ever. There are instances where they notice the similar quirks they shared with their dream-twins, or the repeated conversations they had once before. Normally they'll laugh it off, try to let go.

Move on.

Sarah believes she's handling this quite well. She goes along with her daily routine like nothing life-altering has transpired. Save for the addition of her long absent soulmate. Chuck is like a splash of sun in a dark world. Her formally dark and boring, Chuck-less world.

There was always an essential piece missing in her life. She could never place what that something was. And then the dreams began. She saw his face, heard him speak once and fell hard. Now she's falling all over again. Never does she want to hit the ground. She rather just keep falling.

It's Friday morning when Sarah enters the lecture hall. Today, she leads a weekly recitation with her French Language and Literature class. The discussion consists of hundreds of students, which is slightly unnerving for an aspiring professor such as herself. But she braces herself; standing behind the podium with the textbook opened to the appropriate page. Brushing stray pieces of hair from out of her face, she glances up to find the eyes of every male student enrapt by her presence.

At least I have most of their attention, she thinks wryly.

"Alright," she begins. "Now if you would all please turn to page nineteen…"

Along with the simultaneous unzipping of backpacks, there's another less noticeable sound that taps against the door. Tap. Tap. Tap. Sarah dismisses the noise as a student drumming their pen on the countertop. Drawing a breath, she continues unperturbed.

"If everyone is ready, we can begin today's lecture on a more in depth look at the history of the French Revolution," she pauses to let the class groan. "Bitching and moaning about it won't make this lesson magically go away. Believe me, I've tried that."

As the class settles down, the tapping resumes more incessantly than before. This time Sarah hears it. She scans the room packed with students to find no one is causing the disruption. They collectively stare her down, bored.

She blinks confusedly. "So, who would like to volunteer reading the first excerpt from the chapter?"

It's dead silent. Then a girl, who trades brief glances with another student beside her, timidly raises her hand. "Miss Walker, I think there is someone outside trying to get your attention."

The entire class shifts their interest towards the door. Sarah turns to look as well, only hesitating when her phone starts to vibrate on the wooden desk. Students snicker, gossiping in hushed tones as she receives an incoming text.

She sighs. "One moment please…"

Picking up the phone, she studies it. The text is from Chuck. Her brows furrow as she reads the message: I know this is sort of inconvenient, but we need to talk. I'm outside your room. :]

Sarah types a quick reply: K.

"Something personal just came up," Sarah tells the class quickly as she stashes the phone in her purse. "So while I go attend to this, now would be the time to actually do your weekly readings. I expect for all of you to be able to tell me how Charles Dickens' A Tale of Two Cities ties directly to the actual events of the Revolution. Your responses must be in French."

She darts out of the room before they can shout their protests. Slamming the door behind her, Sarah is met with an empty hallway. She looks to her left and finds Chuck leaning against the wall, fiddling with phone.

The sound of her stilettos clicking across the tiled floor causes him to lift his head. Sarah notes his flustered appearance; face red like he'd been running a marathon. Or racing from one end of the campus to the other. His exhaustion does not stop him from giving her the once over whilst grinning in that charming Bartowski way.

But his inherent charm won't work today. Sarah isn't amused by his abrupt entrance. She's irritated that Chuck has interrupted her in the middle of class. Probably for some trivial nuisance that doesn't require her immediate involvement.

With arms folded over her chest, she stares at him with poorly disguised impatience. "I have a class to get back to, so you have two minutes to explain. Start talking, Chuck."

Chuck is not put off by the severity in her tone. His smile grows wider. "If I had more professors who looked like you back at Stanford, I would've probably made a better effort to actually attend my classes."

It is all Sarah can do to not roll her eyes.

"I'm sure you would've reconsidered once looking over the course material."

"What are you teaching?"

"French," she replies.

Chuck pushes off the wall and pockets his phone. Strutting up to her, he sets his hands on either side of her waist, backing her slowly against the door. He wiggles his brows seductively. "You mean the language of love?"

"Yes," she says trying to keep her voice neutral. "And its culture, history and influences both in Europe and internationally since its founding during the Early Middle ages."

"Yikes, well I bet most of your male students are now regretting their decision to join the class."

Sarah circles her arms around Chuck's neck, fingers playing with his stray curls. "As far as I'm concerned, they got what they deserved." She shrugs. "Anyway, what brings you to UCLA?"

He gives her a light peck on the lips before answering. "You are not going to believe the morning I've had so far, babe."

"You look like you were sure in a hurry to get here. Must've been some morning. What happened?"

"Can we discuss it over lunch?" he asks.

She sighs and shakes her head. "You know I can't just leave my class. If the attending professor finds out that I've been neglecting my duties, I can lose my job."

He stares pleadingly at her. "Right, but this is sort of an emergency."

She remarks dryly. "I find that somewhat hard to believe considering you wanted to discuss it over lunch. Tell me if this is life or death, Chuck. Be honest."

"If I say maybe, will that be enough incentive to come with me?"

Sarah studies him while he nervously waits for her decision. "Fine," she relents and Chuck looks relieved. "But on one condition."

Chuck smiles, but it's a puzzled smile. "Anything milady."

"Come with me."

And Sarah surreptitiously grabs the handle behind her, wrenching the door ajar. She takes Chuck by the arm and ushers him inside the crowded lecture hall without further explanation.

Chuck gulps.

There's an estimated hundred pairs of curious eyeballs currently fixed onto him. He stands in front of the class and remains abnormally still as they track his every move. The girls seated in the front row are ogling him with flirtatious smiles while the guys look either angry or depressed. Meanwhile Sarah is making use of the whiteboard behind him. She jots down a few reminders; none of the students are copying the notes.

Suddenly she addresses the class. "I'm sure everyone here will be overjoyed to know that class will be cut short today. Something personal has come up. So, read the homework assignments on the board. Finish A Tale of Two Cities since I know about seventy-five percent of the class did not get passed the first sentence. Then write a three page paper on your thoughts about the novel. Je ne devrais pas avoir à vous rappeler tout ce qui est doit être en français." She nods. "Avoir une bon week-end."

At once, the students begin to pack up and vacate the room. They're talking amongst themselves as they shuffle out of the door; not being subtle in their complaints about the class.

Sarah goes to the desk and collects her things, slinging a handbag over her shoulder. Chuck turns to her, his eyes full of wonder. He feels a swell of pride for Sarah. How she has this innate ability to take control of any situation, despite whom or where she is at the moment. He is about to tell her this, but loses his chance when a young man brushes past him, approaching Sarah with a nervous smile.

Chuck furrows his brows. He looks awfully familiar.

"Hi, um Miss Walker?"

"Brody, you know that I'm perfectly fine with my students calling me by my first name," she assures him. "What's up?"

He shifts on the balls of his shoes. "Right, Sarah. Uh, you know how our finals are coming up soon?"

She nods. "God help us all."

"Well, I saw on the syllabus that part of it includes an oral presentation," says Brody. "I get sort of freaked out when I have to speak in front of a large group of people, so I was wondering if you weren't too busy sometime next week, maybe you could help me overcome my fear?"

At first Chuck thinks that the kid is being sincere. He's just a student who needs an extra bit of help. So naturally he'd approach an instructor. But giving Sarah a sidelong glance, he sees how remarkably cool her demeanor has become.

Her frigid look is accompanied by a startling realization. She's in Agent Walker mode. Wait, why do I still remember that?

Perplexed, Chuck decides to intervene before Sarah miraculously pulls out a combat knife from her bra. He clears his throat. "Hey, this isn't the best time to be asking her for a favor. You heard that she is sort of in the middle of a personal situation, and needs to be on her way—"

Brody cuts him off. "Oh, I'm being totally inconsiderate. How about we just trade phone numbers so that way when you're free, you can call or text me the next time you're available?"

Sarah bristles. "Brody, you know perfectly well that I cannot exchange numbers with you. However, I'd be happy to email you this weekend regarding what extra help you'll need with concerns to your final." She tries to sound pleasant but her abrasiveness is evident. "Until then, enjoy the rest of your Friday."

Her rejection is flawless. Brody dips his head and looks sullen. Chuck hears him mutter an expletive under his breath followed by his phone ringing to the tune "Anyway You Want It," by Journey.

A sudden feeling of detachment befalls Chuck. His eyes are trained on Brody but he stares right through him. Then it clicks and he knows.

The Broadster!

A disembodied voice snidely remarks: Wait, isn't he supposed to be dead?

Are you stupid? The second voice replies. Of course he isn't dead. Look, he's right there. Alive!

No, he was definitely stabbed. In Castle, remember? He was a candidate for the new Intersect program. The first voice adds. Oh and look, he's hitting on your wife.

Girlfriend you mean?

No, wife. Mrs. Sarah Lisa Bartowski.

Well, I don't see a ring on that finger. Do you?

And they're back. Nearly of month of blissful silence and now it's over. The two voices have picked up where they left off; discussing their unwinnable argument. Chuck feels a migraine coming on, and wants to scream. He doesn't care which of them is right. He just wants it to stop.

"Chuck."

Sarah calls out his name and he snaps back to reality. He finds that Brody is no longer standing in front of him, answering his phone. Its Sarah instead, her face full of concern.

"Are you alright?" she asks. "You zoned out."

It's no biggie, I'm just thinking in to different voices again. Chuck won't dare say it aloud. There is no reason to worry her yet. He smiles weakly. "I'm fine. Let's go get some lunch, huh? I have a lot to tell you."

Sarah studies him for a few moments before nodding her consent. Taking her by the hand with fingers interlocked, he leads her out of the room. His mind is torn asunder by conflicting thoughts; the battleground for his waning sanity once more.

It's a pleasant day so Chuck and Sarah decide to enjoy lunch outside. They find a bench near the campus quad and sit on opposite ends; both eating a shared deli sandwich. Sarah munches on her half (the one with extra pickles but no olives) while Chuck looks on with a trace of a smile on his lips. The voices have calmed down but not disappeared. They are ever-present and murmuring. To Chuck its plenty annoying, yet manageable.

As he unwraps his half the sandwich, Chuck remarks. "So do you deal with a lot of Brody's when you teach? Or was that a onetime thing?"

Sarah dabs the corners of her lips with a napkin, hiding a smile. "What? You mean rejecting hormonal, sex-crazed college students?"

Chuck gives a noncommittal shrug.

"I consider it part of the job description," she says half-jokingly. "Besides, there's nothing really to worry about now that they know I have a boyfriend. Word will spread like wildfire and by Monday, every male student on campus will back off."

Chuck raises his eyebrows. "Now I see. So that's why you forced me to stand in front of them like a complete idiot. That's diabolical, Miss Walker."

Sarah sips her coffee. "Just be glad that I didn't take it a step further and have you kiss me instead."

"You say that like it's a bad thing." He stares directly into her blue eyes and drops his voice an octave. "Had I'd known the plan, I would've taken you on the desk right there with no questions asked."

He observes the subtle dilation of her pupils and the shift of her body as though she had shivered. "Tempting, but unless I'm mistaken, sex in public is a form of public indecency and a felony."

"And now you're apparently a Criminal Justice major too?"

"Only when it comes to sex crimes," replies Sarah with an exaggerated wink. "But in all seriousness, what were you going on about earlier that was so important?"

"Oh, right I almost forget." He chuckles lamely. "Well, as you know, I've been pulling all-nighters this entire week trying to finish this new program." When she nods, he goes on. "I blame it on sleep deprivation mostly, but this morning while my computer was running diagnostics on the software, I busied myself by drawing in my notebook. Low and behold, this was the finished product."

Chuck retrieves a folded piece of paper from his pocket and flattens it out on the bench's surface. Sarah sets her coffee down and studies the image. Her eyes widen. Let this be a joke.

"Do you remember this?"

"Yeah," she admits softly. The feeling of déjà vu creeps up on her like a spider. "I wouldn't forget that."

It's the picture. The picture replicated from her dreams. Chuck had drawn it on the bullet train in Japan. They had made love beforehand. Then he found a photograph of a house in some magazine and started doodling all over it with images of their perfect future.

Sarah doesn't trust herself to say it aloud; her throat full of tears. The end is so near that I can taste it.

This rendition of the sketch is eerily similar to the one she remembers in her dreams. On lined paper, Chuck had drawn the house and picket fence with them both standing in the foreground, a tiny child resting in her arms.

A little man, or wo-man, she recalls faintly.

She stares transfixed by the drawing, totally lost.

"I was dozing off when I sketched it out," he explains. "I don't know if I actually fell asleep, or was just daydreaming. It's sort of freaky, isn't it?"

Her voice wavers. "Is this what you wanted to show me?"

He shakes his head. "No, that's one of them though. On my way here, I was pulled over by a cop for going just a tad bit over the speed limit." At Sarah's dubious glare, he amends quickly. "Alright, so I went ninety in a sixty-five zone. But that's not the point. The cop who caught me wasn't even highway patrol. I looked him up afterwards just to make sure that I wasn't going completely crazy."

"Don't tell me that it's…" she trails off worriedly.

"—Sergeant Alexander Coburn of the LAPD," finishes Chuck.

"Better known as Colonel John Casey."

"One in the same," nods Chuck. "He's recently divorced to Katherine Coburn nee McHugh, and has an eighteen year old daughter, Alexandra. She took the Coburn name, goes by Lexie, and apparently is an incoming freshman at—you guessed it— UCLA."

Sarah looks at him helplessly. "Why is this happening to us?"

"I'm working on it, trust me," he assures her with a smile. "I think it came just as a big shock to Casey as it had to me. I accidentally called him out as Casey rather than Alex and it really freaked him out. He forgot to write me up for a ticket and just bailed."

"So he remembers then?"

"That's always a possibility. It seemed like he sort of recognized who I was, but not quite you know?" His expression turns thoughtful. "At any rate, this gives me the motivation to start researching."

Sarah blinks. "You are serious about this?"

"Aren't you in the least bit curious to know what this is all about?"

"I thought we were done with this," she mumbles sadly. "Like we'd forget everything and finally move on."

"I don't think we can. Not yet anyways."

"You said we would."

"I was wrong then."

She blows a sigh of exasperation. "Since that morning at the beach, we've been forgetting just fine. Now we're not. What changed?"

"I don't know," says Chuck truthfully. "Have the voices come back?"

Sarah averts her gaze. "Yes," she whispers.

Chuck mutely stands up and rounds the bench. He slides beside Sarah, rubbing her back with his left hand while pocketing the drawing with his right.

"I can hear the voices again too," he confesses. "They're a lot stronger than before. The one that's convinced that those dreams are something more is leading me to believe its right."

Sarah shuts her eyes and leans against Chuck. He presses his lips on the crown of her head. "What are you thinking?" she asks. "What should we do?"

"I've been browsing the web this past week, and it seems to me that these dreams, considering we've both had them, point to something akin to alternate dimensions." He pauses when she snorts humorlessly. "Have you ever heard of quantum physics?"

"Chuck, I'm a professor at UCLA. Of course I've heard of quantum physics."

He blushes. "Well, anyway. One of the theories has to do with alternate or parallel dimensions. For every action that we ever get to make, there is a universe where all the other options are taken, as opposed to the ones you're fulfilling presently. That's just one of the many ideas theorized. So I found this book that goes into detail about the other proposed ideas, and I put it on reserve at the university's library."

"Do you honestly believe that what's happening to us has to do with alternate dimensions?" asks Sarah, raising her head.

"That's the only logical explanation I've found so far."

"Please tell me if you figure it out," she says tiredly. "I have office hours in fifteen minutes, so I can't join you at the library."

"How long will you be?"

"Two hours."

Chuck kisses her again. "Listen, I'll meet you at your office once you're free. Just hang in there. I'm going to fix this. I promise."

Sarah watches him rises to his feet, a smile ghosting her lips. "By the way, what was the title of the book you're so keen on reading?"

"It's called The Philosophy of Time Travel," he tells her. "Do you know it?"

"No."

"Well then you will in a little bit!"

With a final dazzling smile, Chuck walks off towards the south end of the campus. His untamed curls dancing in the wintry breeze. Sarah sits at the bench, waiting for him to disappear amongst the mesh of students and faculty.

There goes your goofball husband, says a faceless voice. He's sure developed quite the hero complex, hasn't he? He always feels obligated to save you.

The second voice interjects: He's your boyfriend. Your average, ordinary, not superspy boyfriend. And he is just as mad as you are.

But he loves you, reminds the first voice.

The other acquiesces. Yes, he loves you.

Sarah finds it reassuring that though the voices cannot stop arguing, they can at least agree on a single simple truth: she will always love Charles Irving Bartowski. No matter where or when. She will love him.

Knowing this keeps her wholly content.

An: Ah, now shall I assume that some of you are confused? Even just a wee bit? Let me see if I can alleviate the confusion a bit.

1. Chuck and Sarah start dreaming about the other universe on the night of September 18th aka Chuck's 26th birthday. This is the night where he originally is supposed to inherit the Intersect from an email from Bryce.

2. These dreams span anywhere from October or early November. I'd say each dream is like an episode of the show. so 91 dreams that can either be sleeping at night, a daydream, or a nap. This can be condensed to the allotted time I spoke about earlier. When the dreams end, the voices remain. Chuck is finally drawn to Sarah and vice versa on the beach where they finally reunite.

3. A month passes since then. So we're looking at late November or early December. The dreams have ended permanently while the memories they've sustained are fleeting. Yet deja vu remains, and obviously so does the sleepwalking and voices per this chapter.

Next update: Chuck will present his theory ( a very confusing, convoluted theory) to Sarah, and some interesting things will be brought to light.