***Author note: I'm not too interested in messing with canon so think of this as a brief interlude and shared secret between Sarah and Ellie. Consider it complete unless I decide to update later. Set some time between season/episode 2.1 and 2.2.***

A/N 2: This story started as a one-shot but has since expanded which does deviate from canon. I'm leaving the first note above because those were my initial thoughts when I first had this idea but I also wanted to give a warning to those who don't like AU stories. Sarah/Ellie pairing.


Sarah knocked on Chuck's and Ellie's apartment door. A mission a few hours before had required more physical agility than she'd expected and she was feeling some cramping in her hamstring area of the left leg that wasn't going away. Chuck was at the Buy More and she knew Ellie would be home so she figured having Ellie take a look before heading to the Orange Orange might save her the hassle of going through CIA-approved medical support.

Ellie opened the door. "Hi Sarah! Chuck's not here, he's at work."

"I know," she replied. "I'm actually here to see you. Can I come in?"

Ellie waved her in. "Yes, of course, it's good to see you, I was… whoa! You're limping, are you okay?"

"Yeah, well, no. I have this cramp that isn't going away and I'm worried I may have pulled something."

"What were you doing?"

"I went for a run this morning and who knows, maybe I didn't stretch enough beforehand. Or I'm just really sore," she said as she collapsed on the couch. "I was kinda hoping you could take a look? But I understand if you're too busy…"

"No, of course I can. Just a second," Ellie walked over to the kitchen. "I'm roasting a couple of small chickens for the week. They're done now, I just need to take them out to rest."

Sarah listened rather than watched as Ellie fussed a bit with the roasting pan and aluminum foil. She envied Ellie's culinary prowess. If she'd had more time she'd love to be able to cook more. More than a few times she'd asked Chuck to schedule dinner at his place rather than go out for cover purposes because she just loved their home-cooked meals, the relaxed atmosphere with friends, Chuck's company. She smiled to herself when she thought about the last dinner when she had placed a hand on his thigh while at the table. He nearly jumped out of his skin. She shouldn't have done it given how she'd already screwed up by kissing him when she thought they were going to die but it had just seemed a natural thing to do with him, like she was his real girlfriend.

"Okay, it was the left leg, right?" Ellie asked matter-of-factly as she moved the coffee table to make more room for the examination. She was dressed in a tank top and pajama pants, making a day of hanging out at home. Sarah again envied Ellie.

"Yep. I just want to make sure it's not anything worse than soreness, I can't miss work."

"Of course. It's a good thing you're in a tank and some comfy shorts, can you lie on the floor in front of the couch on your stomach? I'll be bending your leg and touching your thigh."

Ellie knelt on the floor and Sarah did as she was told. The pain didn't seem to get worse by bending or straightening the leg. Ellie pressed her fingers into the back of her thigh. Sarah grimaced a bit but she made no sound.

"Is that where it hurts?"

"Yes," Sarah said through gritted teeth.

"I feel some tightness but no divots or bulging, which is good news. I don't think it's a hamstring strain. Just soreness or cramping. Nothing some good stretching, rest, and Motrin can't fix. Let me help you up so you can lie back along the length of the couch, yes that's it. I'll help you stretch a bit, like a physical trainer. It doesn't happen often but even Devon needs me to help him with stretches sometimes."

She crinkled her forehead as she thought about the best way to do this leg stretch. With Devon she had no qualms about putting her body against his but she didn't want to be presumptuous with Sarah.

"Okay, so I'm going to put my knee between your legs and I'm going to hold your leg up and press it back towards your chest."

Sarah laughed. "Sure, no problem." She spread her legs a bit to let Ellie get her knee on the couch then tenderly lifted and rested her left leg on Ellie's right shoulder. "Let's just hope the guys don't come in or this could get really awkward." Sarah's eyes narrowed on a suddenly tensed up Ellie. Her joke had been meant lightly and she was curious about the nervousness she now detected in Ellie.

Ellie smiled and bit her lower lip, imagining Chuck's face at seeing his sister rubbing his girlfriend's very smooth thigh. "Yes, I can only imagine what they would think." She'd tried to push it out of her head but Sarah voicing the scenario only put other, more graphic, images in her head. Sarah was a beautiful woman; her eyes and smile betrayed a worldly knowledge Ellie didn't think her brother fully grasped. She was also impressed with Sarah's obvious physical power – it'd been something she missed before but now she couldn't stop thinking how strong these legs were. Her right hand absentmindedly rubbed Sarah's leg from her ankle down to her knee and she cleared her throat when she saw Sarah's eyes opened wide at the movement.

"Uh, sorry, I'm used to doing this for Devon," Ellie said quickly.

Sarah didn't say anything. She tried to look relaxed but her senses had never been more on alert.

At first Ellie tried to just use her hands to push against Sarah's calf and the back of her knee but she was having trouble concentrating and maintaining a constant pressure.

"Ellie, it's okay. Just use your body. I know what you're trying to do and it'll be easier if you just do it the way you do with Devon, okay?" Wait, did I really just say that? she thought to herself. Sarah wasn't naïve, she could tell Ellie's touch on her leg had been more than a friendly rub. A warning bell in her head was going off but the tingle she felt told her to ignore it.

"Right, okay," Ellie softly answered. Placing Sarah's leg against her chest, she leaned forward and placed her right hand on the couch's armrest next to Sarah's head. She could feel the back of Sarah's thigh against her stomach and she cleared her throat as she put her left hand on Sarah's leg, hugging it against her.

The physical contact with Ellie was making Sarah feel warm. Her face was very close to hers and as Ellie pressed down further, Sarah couldn't help the small moan that escaped. She glanced down the front of Ellie's tank top, and quickly looked away but there was no ignoring the heat pooling between her legs. Feeling Ellie's breasts against her leg, inhaling her scent, it was becoming too much. Her normal defenses had been worn down lately by Chuck's adorableness and the stress she'd been feeling at having to suppress her feelings for him was at a breaking point. Perhaps she needed to prove to herself that Chuck didn't really mean anything to her. That's how she explained it to herself later when analyzing what she did next: she brought up her right knee so that it was against Ellie's hip.

Ellie's eyes quickly sought Sarah's but Sarah had her head turned with eyes closed. Ellie was reminded of the times with Devon where these stretches turned into romps on the couch. Feeling a leg against her side would usually be a sign to escalate contact but this was not Devon. It had been years since she'd been with a woman. Sarah's quick, short breaths, the tiny beads of sweat on her forehead and her chest, and that small moan earlier were telltale signs of arousal. Knowing Sarah was aroused stirred something in Ellie. Against her better judgment, Ellie gently slid her left knee under Sarah's right thigh, placing more of her middle against Sarah's. Sarah responded by putting her hands on Ellie's arms and squeezed lightly.

"Sarah, is this okay?" Ellie asked.

"Yes," Sarah answered breathily.

Ellie was nervous, aroused, guilty. She knew Devon and Chuck would never forgive her if they found out but the sudden desire she felt urged her on. It was spontaneous and exciting, and not like her at all. Her mind screamed at her to get off Sarah but instead she pressed in a bit more against Sarah's leg, moving her left hand down to Sarah's right thigh. She wanted to give Sarah a chance to back out, though.

Sarah knew Ellie's movements against her had crossed over into a more heated connection. She knew she didn't have any sort of romantic feelings for Ellie and she seriously doubted Ellie felt anything for her. Whatever was happening right now was pure lust. She could only pray that Casey wasn't monitoring live and that she could get to the surveillance tapes to erase the incriminating footage before he saw it.

"I'm just going to… um… increase pressure, release, and repeat… is that okay?" It was hard to get the words out but Ellie looked straight into Sarah's eyes with this question, her right hand gripping the armrest tightly as she waited for Sarah's answer. The stretch had gone on long enough and they both knew it. Sarah knew exactly what Ellie meant; she was giving Sarah one more out. Sarah thought of Chuck and knew she should stop. She would be cheating on her cover relationship and inducing Ellie to cheat on her very real relationship. But just this once, she promised herself.

"Sounds good to me, Ellie," she whispered and rubbed her right leg against Ellie more meaningfully.

Ellie adjusted so that both of Sarah's legs wrapped around her waist. With her right hand back on the armrest and her left gripping Sarah's right thigh, she thrusted forward. Ellie watched as Sarah's eyes fluttered closed, biting on her lower lip. She focused on Sarah's breathing, changing pressure to see how it affected Sarah. With her left hand she traced circles down Sarah's neck and chest, lightly caressing her breasts, still slowly pumping against her.

Sarah's grip tightened on Ellie. She arched herself up slightly so that their chests were closer together, brushing her lips lightly across Ellie's. Ellie put her forehead against Sarah's and they moved against each other, finding a rhythm. Their shallow breaths, gasps, and light moans were the only sounds in the room. Sarah brought her hands to Ellie's face and pulled her into a deep kiss. It was both gentle and urgent and Ellie melted against her, moving kisses down Sarah's neck as Sarah removed Ellie's hairband which had held her hair up in a ponytail, her hair falling forward over their faces. Sarah could feel her release approaching and was torn between racing toward it or breaking away. This was dangerous.

"Ellie," she started, "this is… mmm…"

"Crazy?" offered Ellie into Sarah's ear before biting on her earlobe, their breathing growing more ragged. "Have you ever done this before?"

Sarah shook her head lightly and managed a weak, "Not really." She was rubbing her hands along Ellie's back and licking along her jawline before throwing her head back just as Ellie pinched her right nipple. She'd had to seduce a couple of women on assignments before and while one had been pleasurable, it was still part of a mission and not born out of her own wants and desires. This was something entirely different. Doing this actually endangered her assignment. It was everything she was not supposed to do.

Ellie felt adrenaline and desire surge through her body. Sarah was coming undone beneath her and it was incredibly intoxicating. Everything she did seemed to drive Sarah wild, especially all the attention she was giving her neck and Ellie was happy to oblige with more kissing, licking, and sucking. Sarah loudly moaned and tightened her legs around Ellie.

"Sarah, are you going to come?" Ellie whispered into Sarah's neck.

Ellie's brazen question almost sent Sarah right over the edge. Instead she bit down on Ellie's shoulder, pushing the tank top strap out of the way. The absurdity of dry-humping her cover-boyfriend's sister was not lost on her. The attraction she felt for Chuck was drowned out by Ellie's whimpers at her bites. Sarah thought of Chuck's smile when she slipped one hand under Ellie's waistband and gripped her ass. She thought of Chuck's lips as Ellie returned her bite with a bite of her own on her neck and massaged the pain with her tongue; his hands when she cupped Ellie's breast with her other hand. She tried not to think about what the company's psych people would say if they knew how these conflicting thoughts were only going to heighten the orgasm about to hit her. She brought both hands to Ellie's ass, pulling her in tighter while thrusting her pelvis against her, then slipped one hand inside Ellie's pajama pants seeking out her center.

Then they heard a key being inserted into the door's lock. Somehow they both knew the looks on their faces would've been too hard to explain if they broke apart completely and so they wordlessly adjusted back to the initial stretch position. The door opened and in walked Devon.

"Ladies! How's it going? I see Ellie is working her magic. Sarah, bit off more than you could chew, eh?" Devon nonchalantly strode around, removing his bag, and going into the kitchen to raid the refrigerator.

"Um, yeah!" Sarah called out. "I felt something while running this morning. Ellie was very kind to help." She then stared hard at Ellie who had suddenly put her right hand over her heated center, rubbing, massaging, intending to finish what they started, even with Devon in the kitchen. Keeping a straight face took all of her skills as an agent. Getting caught was not an option. Thankfully she had been on the cusp anyway and within 5 seconds she was biting her right hand to keep from crying out.

Ellie was stunned. She couldn't believe she continued even after Devon walked in. She tried to contain the panic that was rising up within her but the look Sarah gave calmed her. It was a mixture of tenderness, friendship, and a touch of regret.

"I think that's enough now, Ellie, I've got to get going."

"Sure, no problem," Ellie said a bit stiffly, as she stood up and moved to get the coffee table back into position. They were both a bit out of breath but Devon didn't seem to notice. Sarah laughed like nothing had happened and grabbed her purse. Ellie marveled at how easily Sarah had shifted to lies and fake smiles.

"Ellie, the chicken smells amazing," Devon said as he walked over to pull Ellie into a hug. Sarah watched as Ellie closed her eyes and leaned into it. Sarah felt no jealousy, only guilt. She went too far with Ellie. Her plan now was to get to Castle and erase the surveillance tapes. Then she would try to forget all about today.

"Guys, I've gotta run. See you later!" she said cheerfully as she walked toward the door. She was still limping but the stretch had helped a lot.

"Sarah, wait. I've got some last minute doctor instructions," Ellie said as she followed her out, closing the door. They were alone in the courtyard and Sarah was desperate to escape.

"Ellie, about… what happened…" Sarah waved towards the apartment.

"I know. It was a mistake."

"Right!" Sarah said hurriedly. "I'm so glad you understand. I don't know what happened but I really like Chuck and I… well, this can't happen again." Protect the cover, Sarah, she told herself.

"God, it was insane and I can't... I mean, I love Devon! I hope you don't think I'm the kind of person who does that all the time. It was totally… I just…" Ellie trailed off, covering her face with her hands and taking some deep breaths, which didn't help since her hands smelled like Sarah. She quickly brought them down and laughed. She was relieved that Sarah mentioned her feelings for Chuck. An affair with her brother's girlfriend would have serious consequences for all involved.

"Sarah," Ellie reached to hold Sarah's hand. "Thanks for looking out for Chuck. He wouldn't understand… this… so I'd appreciate it if it stayed between us?"

"Of course, Ellie," responded Sarah warmly. "I would never hurt him with this. Or hurt you and Devon." Sarah's eyes moved to Ellie's lips. She tried not to think about them suckling her neck only minutes before.

"Thank you," said Ellie, squeezing Sarah's hand slightly. Her body was buzzing with electricity and touching Sarah wasn't helping but she needed to make sure they could stay friends and nothing more.

"Okay."

Sarah pulled her hand away from Ellie and turned to walk away. She could hear Ellie go back into the apartment. She smiled to herself thinking that if Ellie was feeling half of what her body was feeling then Devon was going to have a great night tonight.

Back at Castle, Sarah was at the controls, carefully editing the surveillance footage, adjusting time stamps, etc. It all looked pretty seamless. She had even made sure any backups Casey had at his apartment were properly dealt with. Casey wouldn't be able to tell the difference.

Sarah felt her pocket for the thumb drive that held the only copy of her indiscretion. She had left Ellie's apartment relieved but still so damned aroused. Some wine and some solo viewing were on the menu for tonight. She called Chuck to cancel their cover date. Just one time and then I'll erase it, she promised herself.