A/N: Okay, this is another one of those things that just kind of came out of my head when I stayed up too late one night. I thought I'd better write it before we actually meet Maura's sister and she inevitably turns out to be nothing like this. (Did she say her name was Caitlin? That's what it sounded like, so that's what I'm sticking with for now.) Her personality is based partly on the production still that I mistakenly thought was her (tattooed and halter-top-wearing) before learning that girl is actually going to be Jane's new neighbor- but I also just tried to imagine what a younger, more blatantly and to-the-point seductive Maura would be like. Oh, and I picture her to look like Annabelle from Loving Annabelle (which I feel weird saying, because that's not a movie I'm sure I'd totally recommend). Anyway, this was the result.

It was one of those nights where Jane might have stayed longer if she thought she was close to making any headway with their latest case. As it was, she felt she had worked long enough today, and besides—she had a date.

Well, not a date date. She had agreed to go by Maura's that evening after work to try some new yoga relaxation methods. Jane still did not particularly care for yoga in any way, shape, or form, but the promise of privacy was tempting. If she fell on her face or her back in front of Maura, it wouldn't be as embarrassing as doing it while surrounded by all those pretentiously fit people in yoga studios who all seemed as though they lived and looked comfortable in a world where Enya was constantly being played.

She ran home to change (slacks were not conducive to yoga) and wound up arriving at Maura's wearing nothing but a sports bra and a pair of shorts. There was also a jacket slung over her shoulder which she had brought in case the breeze picked up, but it never did.

When the door swung open, Jane raised her eyebrows upon being greeted by someone who was not Maura or even Angela. She found herself facing a young woman with dirty blonde hair and hazel eyes that were widening as they took in the sight of Jane's fairly unconcealed body.

"Uh…hello," Jane said slowly, shifting awkwardly on her feet. "I'm—uh, are you…?"

The girl shook her head as if trying physically to clear it, then said, "Hi! I'm sorry; I'm Caitlin Martin."

"Mart—oh! You're—you're Hope's daughter?"

"Yes! And Maura's half-sister. Please, come in," Caitlin said, stepping back and gesturing inside. She closed the door after Jane and said, "Sorry, um… did you guys have plans…?"

Jane raised an eyebrow, wondering why there was a certain edge to Caitlin's anxious tone. "Yeah, we did, but y'know, nothing serious. I don't know if you've noticed, but Maura can be a little absent-minded sometimes!"

"Yeah, I—sorry, this was really last-minute. My coming over here, I mean. My—or, our mom thought it would be nice if we spent some time together, and I've got AP's coming up in a couple weeks, so this is sort of my last weekend to spare before the crazy studying begins!"

"Oh, well, I don't want to intrude on your sister time," Jane said, already heading back for the door. "I think that's really sweet."

"No, don't leave! We've already spent most of the day alone together anyway, and you guys had plans for tonight!"

"Trust me, Caitlin, you'll be doing me a favor. She wants us to do yoga, so…"

In the type of authoritative tone Maura used when she was overriding Jane's tendency to leap to conclusions, Caitlin pointed a stern finger at Jane and said, "Don't you go anywhere, uh…"

Jane quickly stepped forward, extending her hand. "Oh! Gosh, right, I'm Jane! Jane Rizzoli."

"Jane," Caitlin said with a smile, shaking her hand. "Very nice to meet you."

"Likewise. Um, where is Maura, anyway?"

"She was about to take a shower before we settled in for a Twilight Zone marathon."

"Oh, well—"

"I'll be right back," Caitlin said, already walking towards Maura's bedroom. She glanced over her shoulder to see Jane resignedly placing her jacket on one of the dining table chairs and sitting down. Giving Maura's door a quick knock, Caitlin cackled and slipped inside the bedroom.

Maura was wearing only her towel when Caitlin came bounding in. "Is everything all right? Was there someone at the door?"

"Yeah, it's your girlfriend. Apparently you guys had plans tonight?"

"My…?" It only took Maura a second to realize who Caitlin was talking about. "Oh, you mean Jane? We—oh, shoot! We were going to do yoga tonight; I completely forgot—but Caitlin, we're not …I mean, Jane's just my friend."

Caitlin merely raised an eyebrow and folded her arms in disbelief. "What now?"

"We're friends. Not like 'friends' friends—just friends."

"Maura. It's okay. You don't have to lie to me, I swear."

"And I swear I'm not lying to you. Trust me, when I try to lie, I break out in hives. It's ugly. You can ask Jane yourself."

"Oh. I will."

Her tone still clearly indicated intense skepticism, which Maura found herself getting unduly anxious about . "Caitlin! Why would you even assume that?"

"Um, well, let's count the reasons: you haven't mentioned a boyfriend, it's a Friday night, and Jane came over wearing nothing but a sports bra and booty shorts."

"Jane does not wear booty shorts!"

"Whatever, they're short. Are you really just friends, Maura?"

"Yes! I wouldn't be embarrassed to hide it from you if we were anything else!"

Given how much Maura had already candidly shared with her (to the point where "too much information" had lost all meaning), Caitlin had to give her that one. Also considering Maura's blunt nature and already-obvious quirkiness, it wasn't too difficult to believe she might be telling the truth. "All right, all right," Caitlin said lightly, holding up her hands in a sign of defeat. "I'm just sayin' I wouldn't have blamed you, though. She's pretty hot."

Rather than read anything into it, Maura just chalked this comment up to the casual way teenage girls seemed to talk about other women these days. "Yes, she is rather aesthetically pleasing."

"So you agree?" Caitlin asked, raising her eyebrow again.

"What?"

"You think she's pretty hot."

"I…think she's not…unattractive," Maura tried. "Caitlin, would you feel weird if she stayed? I mean if you do, I can just go ask her if we can reschedule. Otherwise, maybe she'd like to join us for a bit of the Twilight Zone. I'm sure she'd prefer that to yoga!"

"I think that's a great idea, Maura! And you know what, don't you even worry about it—go ahead and take your shower. I'll ask Jane about staying."

Jane looked up from the table when Caitlin reemerged. "Hey."

"Yeah, so Maura would like you to stay, unless that'd make you feel weird," Caitlin said, sitting at a chair across from Jane.

"Oh! Uh…well, if you wouldn't feel weird about it…"

There was something almost catlike about Caitlin's grin. "I wouldn't mind it at all."

"Cool. Okay. I should maybe change into something a little more… appropriate, though."

"Why? We're all girls together."

"Y…yeah, but I think I'd be more comfortable with at least a t-shirt," Jane laughed. "I've got some here anyway."

"You have clothes here?"

"Yeah. Sometimes I wind up staying here longer than… well, sometimes I spend the night, I mean."

And these two aren't dating? Okay… "Uh, cool. Okay. But you don't have to change just yet. Maura actually wanted to get in a little yoga before we vegged out to the Twilight Zone."

"Ah. Okay. So… the Twilight Zone. Your sci-fi-loving mother drill that one into you?"

Caitlin grinned and sat across from Jane at the table. "How'd you know my mom likes science fiction?"

"Maura told me."

"Ah, duh. Yeah, I was pretty much raised on stuff like that. Actually the only time I ever saw my mom get mad at one of my friends was when Isabel Cohen dared say she liked the new version of The Day the Earth Stood Still. I wasn't allowed to hang out with her again for a week."

"Ouch," Jane laughed. She started absently playing with her keys, then finally noticed the way Caitlin was looking at her. The girl was rubbing the back of her neck, all but biting her lip and drooling. Suddenly Jane felt very self-conscious about the fact that she was barely wearing any clothing, and she awkwardly leaned back in her chair, pulling her coat around her. "So! Uh, you've got AP's soon, huh? You a science geek like Maura?"

"Hardly," Caitlin chuckled. "My mom wishes, though. But I think Maura was the only one to pick up that gene. I take more after my dad—I'm more into English and social studies. So I'm doing AP English and AP European history, but also AP stats and AP psychology."

"There's an AP for psychology?"

"Yeah. Pretty cool stuff, as it turns out. I think that might actually be what I want to study once I get to college—BCU, preferably. Just like Maura."

"Wow, cool! Yeah, well, if that's what you do, be sure to remember my name."

"Why, are you a psychologist?"

"What? Oh God, no!" Jane laughed. "No, I'm a cop."

Caitlin let her jaw drop for a moment in brief excitement, and there was definitely a glint in her eye. "You're a cop?"

"Uh…yes," Jane said, getting a bit tense again. "Yeah, we could um… we can always use help doing psychological profiles on suspects and stuff. Gives us a better um… a better idea of…" She trailed off when Caitlin leaned slightly forward, allowing the neckline of her shirt to drop a bit—just enough to give Jane a view of the fact that Maura's cleavage seemed to run in the family. Gah! What the fudge cluster, Rizzoli? Okay, yes, she's legal but—WHAT THE HELL, STOP.

Her eyes snapped back up to Caitlin's when the teenager said, "You probably get asked this all the time, but…" If Maura's telling the truth, there's still no reason why I can't have some fun with this. "Do you ever use the handcuffs with my sister?"

"With your—with—Caitlin!" Well, this girl certainly wasn't shy. Just like Maura. "That is—that is really not appropriate ask question. I mean, that's really not an appropriate thing to ask."

"You're avoiding," Caitlin said in a would-be professional voice, narrowing her eyes and stroking her chin. "It's nothing to be worried about, Officer."

"Detective. But—"

"Sorry. Detective. Don't be embarrassed. I don't take AP physics, but isn't that sort of what the handcuffs would be like? Simple physics? You keep all this energy pent up, boxed in, and when you finally release it, it's like a sexplosion all over the place?"

At the word "sexplosion," Jane was on her feet. "Whoa! Okay, kid—"

"I'm not a kid, I'm eighteen," Caitlin stated calmly. "And my mother spent so much time trying to make sure I never got pregnant that she hardly knows what to say now that she knows considering my taste, it isn't going to happen. Oh she's supportive of it and everything," Caitlin added when Jane's eyebrows raised even higher. "But she's not sure what advice she's supposed to give me other than 'don't have sex, because you will get pregnant. And die.'"

"Heh, Mean Girls," Jane said nervously, now starting to pace slightly.

"Yeah! You got the reference!" Caitlin laughed. "I thought it might be like an age thing, 'cause Maura totally missed it. Anyway, Maura's actually been really great to talk to because she's super frank about everything, you know?"

"Ohhh yeah, I know. So she's told you all about how immunogoblin-ass A can help ward off colds, or whatever?"

"Yes. How long have you guys been dating, anyway?"

Jane practically jumped at the question, having already forgotten that Caitlin had previously assumed Jane and Maura were a couple. She fought to keep her voice flat when she said, "We're not dating, Caitlin. We do not have a sex life. We are just friends."

"Really? She sure didn't make it sound that way."

Jane stopped her pacing, staring at Caitlin with no idea that Maura's inability to lie was not a trait shared by her sister. "W-what?"

"Oh, yeah. She thinks you're smoking hot. Which…you are, if you don't mind my saying so."

"If—uh…she… c'mon, she didn't say that."

"She basically did, yeah. C'mon, Jane," Caitlin said with a crooked smile. "Hasn't a woman ever expressed interest in you before?"

Caitlin's tone had become decidedly less predatory and much more curious, like she wouldn't be able to believe it if Jane said no women had ever hit on her before. Jane quickly tried to assess what she should say, what all was this girl's business, and what the proper response would be. Aggressive as Caitlin was, Jane didn't want to be rude to Maura's sister, and what was the harm in just talking to her, anyway? Besides, if she avoided the question much longer, Caitlin might begin to suspect something.

"Yeah, there was this one time we went undercover at a gay bar. A lesbian bar."

"We?"

"Er…yeah, me and Maura."

"Maura's a detective?" Caitlin asked with faux innocence.

"No, but I needed her on hand to process DNA. Anyway, the bartender hit on me."

"Yeah? Anything happen there?"

Jane tried to pass it off as a humorous experience. "Well, she actually turned out to be a conspirator in the case we were working on, so sadly no." What she failed to mention were the multiple other times women had dropped hints to her—at the gym, on the force, hell even just grocery shopping.

But even without Jane saying anything, Caitlin seemed to pick up that there was more there. "You know why it is, right?"

"Why what is?" Jane asked a little too quickly.

"Why women find you attractive? I mean, besides the fact that you look like you walked off of Baywatch."

"How are you old enough to know Baywatch?"

"I watch VH1 specials!" was Caitlin's way of explaining it. "Anyway—even though you've spent about ninety-percent of your time with me fidgeting and pacing, I can see you've got swagger. And you're a cop, which means you must be pretty hardcore, right? Don't you find that intimidates men a lot? I mean, unless you were dating like an FBI agent or a soldier, chances are you'd be more butch than him. Women eat up that kind of stuff. Also, pardon the psycho-analyzing, but despite what I'm going to assume is usually a bravado attitude, you seem to be really sensitive about the whole women-liking-you-thing. Unless—oh, God," she said, looking horrified. "You're not like, a Republican are you?"

Somewhat put off by the girl's tone, Jane said, "Not all Republicans are homophobes, Caitlin."

"Okay, but are you?"

"Which?"

"A Republican?"

"Independent."

"Okay, a homophobe, then?"

"No."

"So what would you say if Maura asked you out?"

"I'm Catholic!" Jane blurted out.

Narrowing her eyes, Caitlin said, "So…"

"So I'm straight." I have to be.

"Uh-huh…detective, I hope you're not this scared on the job. And I hope you don't cave this fast, either. Otherwise, I'm not sure I feel safe living here in Boston."

Trying to sound patient while also fighting the blush that was crawling up her neck, Jane placed her palms on the table where Caitlin was still sitting and stared her down. "Kid? You don't know me or anything about me. And no offense, but even if you get a 5 on that psych AP of yours, that still doesn't qualify you to come in here and try to psychoanalyze me."

Instead of answering right away, Caitlin folded her arms and returned Jane's stare, looking undaunted. It was almost amusing to her how flustered she had made this hot detective, and was still surprised at how fast she had cracked. "I'm sorry, Detective Rizzoli. Am I making you uncomfortable?"

"Guess it runs in the family," Jane snorted. Were Caitlin anybody else, she would have been beyond offended at where their conversation had gone; but considering she was Maura's flesh and blood, her lack of basic decorum when it came to discussing sex was not surprising, even if she approached it in a vastly different way than her older half-sister.

The sound of Maura's shower running cut off abruptly, and with a sigh, Caitlin stood up. "Look, forgot I said anything, okay? Sorry if I came off as an ass. I'll go tell Maura you're staying. Would you mind getting out the yoga mats? They're in the—"

"I know where they are," Jane said.

Of course you do. "Alritey, then." Caitlin walked back to Maura's bedroom again, knocking on the bathroom door. "Yo, sis? You done in there?"

"I still need to dry my hair."

"Oh. Well can it wait for a sec?"

Maura opened the door and gasped. "Caitlin! You didn't wear that when you were talking to Jane, did you?"

"What?" Caitlin asked, self-consciously tugging up the top of her tank. "What's the matter with it?"

"It's so low-cut!"

"So?"

"Well Jane tends to get very distracted by cleavage—at least by mine."

"She—what the hell, Maura? And you don't think that's incredibly gay?"

"I never said I didn't think Jane was gay; I said we weren't dating."

After mouthing wordlessly at her for a moment, Caitlin threw her hands up in defeat and said, "You are deceptively complex. I do not understand you."

"What's not to understand?"

Caitlin took Maura gently by the arm and nudged open the bedroom door again. From here, they could see Jane from behind, bending over as she tried to get in a quick practice session of yoga before being joined by the pro. Glancing at Maura and seeing she was biting her lip, Caitlin only barely refrained from rolling her eyes. "Go on. Tell me what you see," she whispered quietly enough that Jane wouldn't hear.

Maura's voice was soft and reverent when she responded: "Well, objectively speaking, I see beautifully developed transversus and rectus abdominis, not to mention a perfectly proportioned gludius maximus."

"Yeah, it's a sweet ass, isn't it?"

Maura immediately closed the door and glared at Caitlin. "Please don't speak so crassly about my friend!"

"Then please don't use your technical science jargon! Maura, no pun intended, be straight with me here. What did you mean when you said you don't think Jane isn't gay?"

It took Maura a second to figure out the question. "I simply meant that sometimes, I have perceived several physical markers on Jane's physiognomy which would indicate attraction when she is looking at other women."

"Including you?"

"Possibly. You know on the Kinsey scale of—"

"Oh, my God," Caitlin sighed, holding up her hand. "Please not another lecture on Kinsey. I've heard enough about him to last me about twenty lifetimes, and not just from you—unless you want to tell me where you fall in that spectrum and how likely it is that you would ask out Jane."

"What?"

"Because she already asked me out."

"What?"

"You sound surprised."

"You're just a kid!"

"So?"

"Jane wouldn't ask out a kid. Especially not a girl. Nice try, Caitlin."

"Okay, but if you don't ask her out, I am going to flirt with her relentlessly," Caitlin said. "And it's going to drive you crazy, because you're going to get really jealous. I can tell. I know you think she's hot, Maura. And I know you're already best friends. And she knows where you keep your yoga mats."

"What does that have to do with anything?"

"Girl, please. If a person hates yoga as much as Jane professes to, the fact that you can get her to do it means things are serious. Be honest. Do you like her?"

"Of course I like Jane, she's my best friend."

"Do you like her, Maura. If she asked you on a date, what would you say?"

Caitlin watched and waited patiently for a response as Maura fidgeted awkwardly. Finally she said, "I'd say yes."

"You would."

"Yes."

"Why?"

"Why? Because…" To be honest, Maura had never really thought about the reasons before. It just seemed obvious—if Jane ever got her act together and admitted her attraction to women, Maura would be happy to take their friendship to the next level. "Because she is my best friend. I couldn't refuse her anything."

"Well then, I think the only problem here is that you and I are in agreement that Jane out there is Cleopatra."

Maura didn't follow. "I don't follow."

"Y'know…Cleopatra, Queen of denial?" When Maura still appeared confused, Caitlin took her arms and said, "Denial? Like…da Nile?"

"Oh!" Maura laughed. "Oh, that's so clever!"

"Thank you. If anyone asks, I totally made it up myself."

"So what you're saying is…I need to go out there and be Mark Antony. And… mark… her anatomy…?"

"Er, we'll work on the mnemonics later," Caitlin said. "Point being, you two are clearly into each other and something needs to be done about it. Don't dry your hair. Be reckless. Go talk to her about this. If you don't, you're both going to miserable, and I really don't think I'll be able to take it if I have to see you sadder than you were at the end of The Fox and the Hound."

"Oh my gosh, why did we watch that?" Maura whispered, nearly on the verge of tears just at the sound of the title. "I still can't believe Widow Tweed up and—"

"Maura. Cartoon."

"Right."

"Focus. If I may, I'd like to borrow your shower. And while I'm doing that, you need to get dressed, be brave, and talk to your 'friend' out there."

Maura would never quite understand how it taken only the cajoling of the eighteen-year-old half-sister she had only just recently met to get her in this position. She was standing next to Jane in a tanktop and sweatpants, her hair pulled back into a hastily towel-dried ponytail.

"You okay there, Maur?" Jane asked, sitting against the couch with her knees pulled up to her chest.

"Yes," Maura said, sitting cross-legged next to Jane. "I'm fine. I just had an interesting conversation with Caitlin."

"Boy, she's quite a character," Jane muttered.

"How do you mean?"

"I mean, uh…she really cut right to the chase. No hesitations, no personal boundaries, no nothin'."

"What exactly did she say to you?"

Jane shrugged uncomfortably, avoiding Maura's eye. "Just stuff."

"About what?"

"About me being a cop and not being married and stuff."

"Ah." Maura waited in vain for her heartbeat to return to a normal pace before putting forth another question, "Jane, why don't you ever like any of the men I date?"

Clearly this one threw Jane, and she turned to face Maura in shock. "What?"

Looking determinedly back at her, Maura said, "I thought it was a straightforward question. Why don't you ever like any of the men I date?"

"You really need reasons, Maura?"

"Yes, Jane, I do."

"Well—fine, because… they're all jackasses! What, like, that Dennis guy got you to commit a felony, and he sculpts in the nude. What kind of freakish weirdo sculpts in the nude? And then you wanted to go out with Giovanni, who's a slob and a total caveman. And Garrett—yeah, real nice choice there. And don't even get me started on Ian—what kind of jerk would just come back here, worm his way back into your heart and your home whenever he damn well felt like it, and then just abandon you again?"

"He didn't abandon me," Maura said quietly. "I asked him to leave."

This was new information. "You what?"

Maura took a deep breath. "I didn't want him here anymore. He wore out his welcome." That didn't mean she liked talking about it, though, so before Jane could ask any probing questions, Maura threw in, "Why were you so adamant that I stay away from Tommy?"

"Because! Come on, Maura, it'd be weird. I mean how would you feel if I started dating your—uh…"

"My sister?"

"Exactly! Wait, no."

"I would feel awkward, I suppose, because even though technically she's not a minor anymore, she is a bit young for you," Maura said thoughtfully, stretching out her legs and crossing one ankle over the other.

Jane pulled a signature "Really?", furrowing her brow. "That's all you'd say?"

Turning to look at Jane again, Maura said, "No. That isn't all I'd say."

"Well…" Jane was practically holding her breath, unconsciously leaning a little closer. "What else, then?"

"I'd say…I was offended that if you were going to date one of Hope's daughters that she would be your first choice."

Talking before Maura had even finished the last few words, Jane breathed, "She would only be an idiot's first choice."

"Really?" Maura whispered.

"A horny idiot, maybe," Jane said quietly. "Yeah, she's pretty, but she's no you." Jane's gaze shifted down to Maura's lips as she kept talking, both of them moving closer with each second. "Anyone would have to be a total idiot to choose the junior, less couth version of you."

"What makes you say that?" Maura asked, her voice little more than a breath.

"Just look at you. You're incredible. Brilliant, beautiful, sweet…"

"Sweet?"

This time, Jane's voice was practically a growl: "Yeah, sweet."

Those were the last words that got out before Maura closed the miniscule distance between them and kissed her. It was a soft, gentle kiss that Jane barely returned at first, and when she did, it was only very tentatively. Still, Jane's breath hitched when Maura pulled away.

"I thought you wanted to bring me over here tonight so I could relax," Jane whispered, nodding at the yoga mats. She frowned at Maura's concerned expression, and tried to assuage her by tenderly cupping her cheek. "We obviously have something to address here, Maura. It's not going to be very relaxing for me. At least, not at first. I'm a little on edge."

"You want to talk about this?" Maura whispered.

"I just…kind of can't believe that just happened."

"Neither can I, but it did. Do you want to pretend it didn't?"

Jane leaned again, the rapidness of her heartbeat anything but relaxing. "Hell no," she whispered before taking her turn to initiate a kiss.

It was about thirty minutes before Caitlin finished her shower, and once she got out, she threw on some pajamas and crept over to Maura's closed bedroom door, straining her ears for any sound or movement. Her hearing was exceptionally good, and yet she could make out no words or even talking noises at all. After a few hesitant moments, she walked back to Maura's bed and idly pulled out her phone. By now, Maura and Jane definitely would have heard that the water had been turned off—unless they were distracted by something else.

Caitlin couldn't help herself. She walked back to the door and cracked it open by less than inch. Jane and Maura were nowhere in sight, and Caitlin wondered if they had left before she realized there was a large armchair blocking her view of the floor in front of the television. And now she could most definitely hear what was unmistakably the combination of heavy breathing and kissing.

Chuckling mischievously, Caitlin closed the door again and returned to Maura's bed. After lying there playing with her phone for a while, she couldn't keep from shouting "you're welcome!" loudly enough for the women in the living room to hear her.

A/N: Hope that was all right! I guess I just wanted to do something fluffy and a little implausibly silly after that last angsty thing I posted. Because of that, I know this came off as a bit rushed, but I wanted to keep this to a oneshot. Oh, and the title came from a Mystik Spiral song that starts "little sister, little sister/you came into my life like a twister." It seemed appropriate. If you don't know Mystik Spiral, I totally recommend checking them out - but hurry; they're thinking of changing their name... :)
oh, and P.S.: I'm really very flattered that people are asking for a continuation, but the ride stops here, people. A oneshot it will stay!