AN: I'm back! Sorry for the delay in posting this, I managed to catch a cold during my vacation that turned into a sinus infection, so I've basically been out for the count since getting home…

So, this story came to me one of the times I watched the ep Butterflied over the last few months. The title is a play on the concept "butterfly effect", which is basically that small causes may have large effects

Thanks to WalkerTRngr for the beta help!

Disclaimer: I don't own anything relating to CSI

Warning: This story deals with rape/sexual assault. There is nothing too graphic, but it is pretty heavily implied and discussed, so please proceed accordingly. If this is something you are not comfortable with, but you still want to read the story, send me a message and I can try to help by letting you know when to expect these situations

Chapter 1

Sara stares absentmindedly into the coffee mug in front of her, eyes focused on the liquid whirling as she stirs in sweetener.

"You looking for the secret to the universe in there?"

She jumps a little at Warrick's voice, earning a chuckle as he goes to grab some coffee for himself.

"42," she replies, smirking when he rolls his eyes and huffs at her stupid joke.

"Funny," he says, claiming the seat across from her. He takes a sip, closing his eyes as he swallows.

"Tired?" she asks amusedly. "Didn't you have last night off?"

He opens his eyes again and wags his eyebrows at her. "Exactly."

She chuckles as Nick and Catherine enter the room, Nick going straight for the coffee as well while Catherine sits down next to Sara. A moment later, Grissom completes the party.

"OK, people," he says, calling everyone's attention, and Sara straightens up a little.

Their relationship has been… good, over the last few weeks. After overhearing his little confession to Doctor Lurie, she was expecting him to pull away, avoid her, like he usually does whenever he feels like he's revealed too much or let her get too close, but he surprised her by pairing her with himself the very next shift. Of course, he doesn't know that she was on the other side of the glass in the interrogation room…

She still, sometimes, has trouble meeting his eyes, but it's getting better. She's getting used to the world where her feelings are kind of reciprocated, but he doesn't think it's worth risking everything he's worked for… and maybe it's better this way. Maybe they would have crashed and burned if they gave things a try – God knows her track record when it comes to relationships is less than stellar. Maybe it would have ruined everything. This way, they can remain friends and colleagues.

She tries to tell herself that's enough.

"Catherine, you're with me – DB at The Golden Nugget. Nick, Sara – home invasion with grand theft auto in Summerlin, might be connected to the B&E in Seven Hills last week. Warrick, you need to prep for court tomorrow afternoon, right?" At Warrick's nod, he continues. "You do that, and leave early enough to get enough sleep, but until then, you're on call if anything else comes in."

Sara snags their assignment slip. "I'm driving."

-CSI-

"Hey, Akers, what've we got?" Nick asks as they near the front door where the officer is waiting.

"Two stolen cars – a 2003 Mercedes Benz C class sedan and a seventies Ford Mustang convertible – plus a boat load of electronics," the officer relates. "They basically took everything; I think the only thing left is the alarm clock and a cordless phone unit. A busted safe, Doctor Lurie says there was a few grand in cash, plus some jewelry – family heirlooms."

Sara froze at the name, and now she glances at Nick, who is sporting the same expression she assumes is on her own face.

"Is that Doctor Vincent Lurie, at Desert Palm?" she asks, just to be absolutely sure.

Akers frowns. "How'd you know?"

Nick runs a hand over his face. "He was the lead suspect in a double murder a few weeks ago," he explains. "A nurse from the hospital found with her throat slit in her own bathroom, the dismembered body parts of her boyfriend stuffed in garbage bins outside."

"Oh, yeah." Akers' eyes flash to Sara, telling her he's aware of the peculiarities of the case. "I wasn't working the case, but I heard about it."

Nick turns to her with a concerned look in his eyes and she knows what's coming before he even opens his mouth. "Maybe we should call Grissom about this."

"Why?" she counters, crossing her arms over her chest.

"Come on, Sara," he cajoles. "We both know he kept you away from that case for a reason."

"What exactly do you think will happen if I go in there?" she asks curiously. "He'll see the doppelganger of his dead ex-girlfriend and…"

"The dead ex-girlfriend he killed!" he interrupts her.

"He wasn't charged," she points out, even though she knows, as well as he does, that there's no question of guilt in that case.

"Because we couldn't tie him to the murders, not because he didn't do it!" Nick almost hisses.

"Look, Nicky," Sara starts, "I know you're not going to leave me alone with him, so what's the worst that can happen?"

He groans. "Damn it, now you've gone and jinxed it, Sar! Never say that!"

She has to bite back a smile. "I'll be fine. Promise. Can we get on with processing the scene now? The sooner we get the work done, the sooner we can get out of here."

He looks like he's going to object for another moment or two, but then he sighs in defeat and stalks past Akers into the house.

Doctor Lurie is at the kitchen island, a few papers in front of him that he's frowning down at, a laptop open next to them. When he hears their footsteps, he looks up.

Sara can see his eyes widen when they land on her, and she hates to admit it, but it makes a shiver run down her spine.

"Doctor Lurie," Nick greets him, voice curt. "I'm Nick Stokes, this is Sara Sidle, we're with the Las Vegas crime lab. Do you want to run us through what happened here?"

Lurie glances at Nick briefly, but his eyes soon return to Sara.

"I've been in the Bahamas for two weeks," he starts. "When I got back late this evening, I found the lock on the front door jimmied, and basically all my valuables gone. Cars, electronics, hard cash, jewelry from my parents… even some of my exercise equipment from the basement was taken. The only reason I still have my laptop is that I had it with me."

Nick nods as he listens. "Who knew you were out of town?"

"Most of my colleagues," Lurie replies with a shrug. "A few friends. But none of them would do this."

"Did you notice anything out of the ordinary in the days before you left for your vacation?" Sara asks, holding back a wince when Lurie's eyes trail down her body and back up at her voice.

"Like what?"

"A car you don't recognize, someone hanging around outside that doesn't belong, calls where the person on the other end just hangs up," Nick rattles off.

Lurie shakes his head. "No, nothing I can think of."

"And you don't have any kind of security system?" Sara asks.

"I've been thinking about it," he replies with a sigh. "But you know what it's like, I just never got around to it."

"How did you get to the airport?" she enquires, remembering that the couple from the previous B&E took a cab – maybe that's the connection, an opportunistic cab driver overhearing excited chatter about long vacations from wealthy clients.

"A friend dropped me off," he tells her though, so there goes that theory.

"OK, well, if you think of something, let us know," Nick says. "Did the officer give you a form to fill out so we know what was stolen? We'll need it to get alerts set up with local pawn shops and send out BOLOs for the cars."

Lurie nods at one of the papers in front of him. "Got it, yeah."

"Great, be as specific as you can. We'll start processing the scene, see what we come up with."

Sara feels the doctor's eyes on her as they leave the kitchen and can't relax until they're out in the entryway again and out of sight. "You want to start here?" Nick asks. "I'll take the living room?"

She nods. "Sounds good."

Nick sticks his head out the front door. "Hey, Akers." He waits until the officer approaches. "You stay with her, got it?"

"Nick…" Sara tries.

"I won't move an inch," Akers promises with a solemn nod, crossing his arms over his chest and focusing on her, and she rolls her eyes.

But it is comforting, having him nearby. Especially when, fifteen minutes later, she senses Lurie coming into the hallway behind her.

-CSI-

The processing of Vincent Lurie's home doesn't take very long – just like in the case in Seven Hills, every surface the intruders may have touched has been wiped clean. They lift some fibers from the bedroom, living room, and basement, as well as fingerprints from the outside of the front door, but even if they aren't from the homeowner himself, Sara doubts they'll give them anything to work with. The concrete driveway and walkway don't give them any footprints, there are no tire tracks either on the driveway or the street outside, and none of the neighbors have any security cameras that might help them. She assumes someone would have called the cops if they saw anything suspicious while Lurie was on vacation – it's a nice neighborhood, she saw a sign about a neighborhood watch on the way earlier – so even if they'll obviously send out a few beat cops to go door to door in the morning, she's not expecting anything to come from it.

"You think it's too early to say this is related to the B&E last week?" Sara asks when they're en route back to the lab.

"I think it's a solid hypothesis for now," Nick replies. "MO's similar enough, same kind of neighborhood… You OK?"

She gives him an exaggerated eyeroll. "I'm fine, cut it out."

"Seriously," he insists. "I'm creeped out, and I wasn't the one he kept staring at…"

She sighs. "Was it weird? Sure. But, I mean… you imagine it, seeing someone who looks like the twin of the woman you…"

"Killed?" he interrupts.

"OK, yeah, but leaving that aside. You're telling me you wouldn't be staring if you ran into a person who's the spitting image of someone you know?"

"Fine, I probably would," he admits grudgingly. "Still, I didn't like the way he was looking at you."

Part of her wants to quash his overprotective tendencies, but another part feels touched by his concern.

Plus, she didn't like it either.

They get the evidence logged and Nick starts processing the fibers while Sara checks out the evidence from the other B&E and sets up in a layout room to study the similarities closer.

"You find a connection?"

She jumps a little at Grissom's voice, looking up to find him leaning in the doorway.

"Nothing conclusive, because we don't have much evidence," she replies, rolling her neck to get rid of the crick that the last couple of hours bending over the table has caused. "No footprints, no tire tracks, all relevant surfaces wiped clean. There were fingerprints on the outside of the front door, but I expect them to come back to the homeowner, and a few fibers that Nick's processing, but they'll most likely be either irrelevant or useless."

"Don't be so optimistic," he teases, and she rolls her eyes as he moves into the room to lean against the table next to her. He keeps a few inches of space between them, but she can still feel the heat radiating off him. "Had the owner been out of town?"

Sara nods. "Yeah, two weeks in the Bahamas," she confirms. "So far, the only connection we can find, and even that's tenuous – different travel agencies, different airlines, different destinations."

"The first victims had been in New York for two weeks," Grissom muses, scrutinizing the photos of the front doors of both crime scenes. "What about cab companies?"

She shakes her head. "I already thought about that, but no go. Lurie was dropped off by a friend, he didn't take a cab."

His head snaps up at the name. "Lurie?"

She looks away from him. "Yeah, he's the… homeowner," she explains. She was about to say 'vic', but can't bring herself to use the term about the man.

"And you didn't say something?"

The anger in his voice makes her shackles rise. "I just did."

"Come on, Sara, you know what I mean."

"No, I don't," she snaps. "What was I supposed to do? Call and say 'hey, Griss, would you mind taking me off this case? The guy that's been robbed is the man we couldn't put away for killing a woman who could be my twin'?"

He frowns at that. "No, I… I don't know, I just…"

"What?" she asks impatiently when he trails off.

"I don't like the idea of you being anywhere near him," he admits quietly, avoiding her eyes.

The confession rattles her, making her lose her train of thought.

"Well," she starts a moment later, "I doubt I'll need to see him again. Nick can sit in on any interviews."

Grissom nods. "Good, thank you."

She opens her mouth, about to ask why, exactly, he doesn't want her around Lurie, but his phone goes off before she has a chance. He glances at it and offers an apologetic smile. "Sorry, Doc is starting the post for my case. I'll see you later?"

She nods. "Sure."

-CSI-

The next night is Sara's night off. Normally, she would still be at the lab, but she's maxed out on overtime every month since July, and Grissom finally put his foot down last week and told her to stay out of the lab on her nights off unless there's an all hands on deck call, so she reluctantly stays home.

Like usual, though she plans a laid-back evening – maybe a movie and some take-out after running some errands for Mrs. Flores next door – by midnight, her pent-up energy has her fidgeting, so she decides to go for a run to get some of it out of her system.

Before leaving her apartment, she makes sure she has her keys, cell phone, and mace – her neighborhood might be safe, but it is still the middle of the night and she's seen too many assault victims to not be overly careful.

The mace stays tucked in the pocket of her running tights, and she doesn't notice the shadow at the edge of the parking lot, or the fact that it follows her when she gets to the street, before a hand clamps over her mouth.

-CSI-

Grissom hurries down the corridors of the lab, cursing Cavallo and his annoying habit of always cornering him about the budget and other administrative tasks when he's in a hurry. He reaches the break room five minutes after the start of shift, which isn't too bad, all things considered. "Sorry I'm late, Cavallo," he offers as an explanation, earning a compassionate look from Catherine.

"No worries, boss, we don't mind a few minutes of downtime," Warrick offers.

"Good. Well, let's get down to it." He sorts through the assignment slips he hasn't had a chance to look at yet.

"Where's Sara?" Nick asks.

"It's her night off," Grissom replies absentmindedly, handing a slip to Catherine. "DB at the Venetian for you and Warrick."

"Since when does that keep her away from the lab?" Warrick pipes in, picking up Nick's question.

Grissom sighs. "Since she maxed out on overtime every month since the summer, and I told her I'd stick her in Trace with Hodges if she comes in on her nights off from now on."

Warrick snorts. "That would do it."

Grissom bows his head in acquiescence before turning to Nick. "Do you need to follow up on your B&E from last night?"

"Not really," Nick says, shrugging. "The evidence has been processed, the only prints we lifted came back to the homeowner and the fibers aren't anything special. I don't want to jump to conclusions, but I would say we're dealing with the same people that broke into that McMansion in Seven Hills last week. None of the neighbors saw anything, even though there's a neighborhood watch thing. We've got BOLOs out on the stolen cars, even if they've most likely been reduced to spare parts by now, and the serial numbers we have for the stolen electronics, as well as descriptions of the jewelry, are in the database, so if anyone tries to pawn them, we'll get an alert, but there's not much more we can do at the moment."

"Then you're with me. Convenience store robbery gone wrong."

"Clerk killed?"

"Not this time – they've been robbed three times in the past year. The owner finally invested in a gun, so we have a small-time thief with a hole in his thigh on his way to the ER and a traumatized seventeen-year-old clerk."

"Ah."

They split up for their respective assignments, and Grissom waits until they're in the car to bring up the Lurie thing.

"So, the B&E you and Sara worked last night, everything went… OK?"

He sees Nick give him a questioning look out of the corner of his eye. "Sure…"

Grissom sighs. "I know Sara would never tell me if anything… happened, but I trust you would?"

"Of course," Nick replies immediately. "I wanted to call you as soon as we got there and found out who the homeowner was. Sara wouldn't have it. But I made sure Akers was always nearby, she was never alone with the guy."

That's a relief, at least. "Good."

They ride in silence for a few minutes before Nick speaks again. "You know Sara. She wouldn't admit it, but I think he creeped her out a little. He didn't do anything, didn't even say anything, but he kept… staring at her, whenever she was nearby. She brushed it off, but…"

Just the thought of that murderer's eyes on her makes Grissom's grip tighten on the steering wheel. He makes a conscious effort to focus on the road.

"If you need to do any follow up with him, I want you on it," he says. "She's not going near him again."

"Agreed."

-CSI-

Sara groans, stretching her arms over her head.

The sound of rattling metal makes her freeze, and her eyes snap open to find an unfamiliar room. Panic creeping into her mind, she pushes herself into a sitting position, the movement drawing her attention to her right wrist, which is encircled in one loop of a pair of handcuffs.

Frowning, she follows the chain to a wrought iron headboard, where the other loop is attached to one of the bars. Her mind working a mile a minute, she tries to remember what happened.

She had the night off. She went for a run and… nothing. Her head is pounding, her throat is dry… if it wasn't for the fact that she's apparently handcuffed to an unfamiliar bed, she would assume she was hungover, but that doesn't explain how she ended up wherever she is, or why she can't remember anything after leaving her apartment. Or why she's chained to a bed.

Pushing the panic down, she tries to assess the situation.

She's wearing the clothes she put on before leaving for her run – tights and an old, faded Harvard sweatshirt over a sports bra and panties. She knows that doesn't rule out someone redressing her, but why would they bother with putting her underwear back on if that's the case?

The room is empty, except for the bed she's chained to. The only window is a narrow one high on the wall to her left, which makes her think she must be in a basement, and the door on the opposite wall is worn wood. The floor is concrete, two of the walls look to be as well, the other two are rough MDF board, and there's a single lightbulb hanging from the ceiling immediately above the bed, spreading a cold light over her apparent prison.

She stands carefully, waiting until a dizzy spell passes, and then moves towards the door. The chain lets her get a few feet from the bed, and when she tries to move the piece of furniture to get further, she finds it's bolted to the wall.

"Damn it!"

Her voice echoes through the room.

She doesn't even try to reach the window, since the handcuffs are attached to the other side of the bed and the chain doesn't quite reach across it. Climbing onto the bed, she tries to see through the grimy glass instead, but the only thing visible is barren ground and some weeds. It's not quite light out yet, probably around six in the morning, so she must have been out for several hours.

With a sigh, she slumps down on the bed, trying to think of something to do.

The pockets on her tights are empty, meaning she doesn't have her keys, mace, or phone. Lying down on her stomach, she looks under the bed to see if there's anything there that might help her pick the lock on the handcuffs, but no such luck.

She spends a few minutes examining the headboard of the bed, but it seems to be sturdy and none of the bars give even a fraction of an inch when she pulls on them. The same holds true for the bedframe itself – everything is wrought iron and apparently made to last. The mattress is made of foam, and there's no box spring, so no metal springs either.

She drags the bedding – a flat sheet, two pillows, and a comforter – off the bed and considers what kind of damage she might be able to do with a pillowcase. Sure, she could probably cut off someone's air supply long enough to get them to pass out, but she'd need the element of surprise, and with the way the room's set up, she can't hide behind the door or anywhere else, really. Still, she leaves one of the pillowcases off the pillow, tucked under it, just in case she gets an opportunity to use it against whoever her captor is.

She examines every square inch of the floor she can reach, as well as the wall next to and behind the bed, but apart from a splinter, she comes up empty. Finally, she returns to the bed, sitting down on the edge of it so the door is in front of her.

She's not sure how long she sits there, staring straight ahead. When there's the sound of a key turning in some sort of lock from the other side of the door, she jumps up from the bed. She's not sure why but being on her feet makes her feel a little less vulnerable.

The door opens slowly, and all she can think when she sees the man outside it is that she should have known.