Title: Spark

Author: Dwu

Summary: Derek and Casey's anger towards each other ignites latent feelings.

Spoilers: Major spoilers for Male Code Blue.

Author's Note: This fic is slightly AU in the fact that it assumes that Derek never approved of Sam and Casey's relationship but they started dating anyway. Things have been tense between the three since, but especially between Derek and Casey.

Note 2: This is my first Dasey fic, so feedback and constructive criticism is very much appreciated.

Casey loved the shower. The sharp mix of alertness and relaxation. The wet feeling of yesterday leaving her with all it's baggage and frustrations. The solitude. The rare absolute intimacy of curtains and a shut door. No one, nothing could bother her here. Here she found peace for 20 minutes of her day…

Casey near growled at the demanding knocking at the door. "Derek," she muttered to herself before poking her head outside the shower to yell back, "It's occupied!"

"Oh, really? And, here I was, just knocking for fun," came Derek's equally agitated voice, "You may be the dirtiest member of this family but you're not the only one who needs a shower!"

"That's rich coming from the guy who's sports bag is a biohazard!"

"Come out or I'm coming in with you," he threatened.

But, the shower was already off and Casey angrily marching toward her towel. She knew better than to start this sort of war with Derek in the morning. In the end they'd both end up pissed off, unshowered, and late for school. She put on her meanest face as she pulled the door open, chin up and facing him as it swung open.

Derek was clearly poised for retort when his eyes fell on her wet, towel-clad form, face flushed and chest heaving in frustration. His mouth was suddenly and inexplicably dry and he found himself unable to face her for a few moments.

But, Casey went on, apparently oblivious to his inability to maintain eye contact. "I hate living with you."

"Well, top of the morning to you, too, Case," he said, the familiar rhythm of their sparring grounding him.

Casey's eyes darkened sharply as she brushed past him, purposively giving him a harsh bump in the other direction. Derek was sure he would have been angrier if not for the unfamiliar tingles her action sent through his body. He watched her furious form retreat to her room, hips swaying angrily and decided he would need a substantively cooler shower this morning.

"We've got to get a lock back on that door," Casey was griping as Derek strolled into the kitchen.

The McDonald-Venturi clan was busily preparing breakfast and lunch, while Casey stood in the middle of the storm, presenting her case. "I don't know how many times I've had unwanted interruptions while changing or bathing," she continued, sending a particularly nasty glance at Derek.

"Hey, don't look at me," Derek said, left hand up in defense as his right shoved a Pop Tart in his mouth, "She was in there for 10 minutes."

Casey huffed. "Since when is 10 minutes a long time?"

"Since you're living with six other people," Derek replied.

"Yeah, I can shower in under two minutes if I try," Edwin offered from his stool.

Casey and Lizzie rolled their eyes in disgust. Nora tried to mediate. "Look, Casey, I know that ten minutes may not have been long in our old house, but we're going to have to start making some sacrifices now that we're sharing a home with other people."

"That's easy for you to say," Casey near-whined, "You have your own bathroom. You don't have to share it with these, these…cavemen."

"Thanks," Edwin said smiling.

Derek smacked the back of his head. "That wasn't a compliment, doofus."

"What if we agree on 15 minutes?" George suggested.

Casey and Derek seemed to take a moment to consider this, their eyes meeting for brief, reluctant consultation. "Fine," they both muttered.

Lizzie raised her hand before asking, "Can we please add the rule that Edwin has to shower for more than 2 minutes then?"

George nodded and the family broke out into laughter for the first time that morning.

"What are you doing?" Derek asked as Casey stood beside him on the sidewalk in front of their house.

"I know 'standing' must be an awfully big conceptfor you, Derek. But, I thought even you could figure this out."

His scowl was evident as he turned towards her. "Fine. Then why are you standing next to me?"

"We go to the same school, don't we?"

Derek snorted and folded his arms over his chest. "And, since when does that justify us being seen together outside the house?"

"I'm waiting for Sam, okay?" she finally said, agitation coloring her voice.

"Right. Of course," Derek said, rolling his eyes.

"What is your problem?"

"You mean besides you?"

Casey huffed and crossed her own arms now. "Look, I never say anything when you date one of your vapid bimbos. Why are on you my case?"

"First of all," Derek replied, "You and Sam are notdating…"

"Yes, we are-"

"And second of all, I don't go after your friends. If you had any semblance of a social life you could find your own guys to drool over."

"Last time I checked, dating was a mutual act, Derek," she answered pointedly, "I'm not desperate and if Sam didn't like me, too, than we wouldn't be going out."

"You're not going out!"

"Yes we are!"

They glared at each other for a long moment, gazes heated.

"Why is this such a big deal to you anyway? You've been a bigger jerk than usual since you found out about us."

Derek's face reddened as he replied, "I just-I just don't like it, okay."


A flood of unfamiliar emotions passed through him, but Derek denied them, responding with the only response that seemed appropriate. "Because the idea of Sam going out with someone like you makes me nauseous. And, now I have to see you even more than I used to."

They simultaneously winched, both surprised by the harshness of his words.

"Casey," he began softly.

But, she cut him off, "And, what, Derek? You think seeing you everyday is dream come true? You are the most obnoxious, self-inflated, manipulative, heartless person I know!"

A mixture of hurt and anger flickered across his features as they both leaned towards each other, lungs heaving with emotion.

"Hey, guys," Sam called, half-jogging up to the siblings.

They quickly stepped apart and regarded him, glares still firmly in place.

"Hey," they muttered in unison.

Sam's smile fell and pace slowed as he took in their demeanor. "Is everything okay?"

"Yeah, peachy," Casey replied, forcing herself to be peppy as to approached him. And for some reason, Casey made a show of stepping into him, slipping an uncharacteristically affectionate arm around his waist as she looked back at her fuming step-brother. She couldn't identify the strange pleasure she got from his hardened eyes and clenched jaw, but it was a pleasure she wasn't going to deny herself.

Sam smiled a little uncomfortably, caught off guard by her gesture and the anger radiating off of Derek. "Um, are you coming with?" Sam was finally able to get out.

But, Derek just shook his head, sending Casey one last heated look before heading off.

"How nice of you to join us," Derek said, voice dripping with sarcasm, as Casey took a seat beside him and Sam.

Casey scooted close to Sam and shot him a smug look. "I know this will be the highlight of my day," she replied gamely.

Derek couldn't dull the stabbing in his gut when Sam threw an arm over Casey's shoulder, the same sensation he'd been having since they'd admitted their feelings for each other. He'd never felt this way before about any girl, let alone his step-sister. To make matters worst, Casey seemed to be deliberately goading him on as if he was completely transparent with his emotions.

"You know, if you try hard enough, I bet you guys could squeeze into the same shirt," Derek bit out.

Sam frowned and Casey openly glared at him. "Oh, please. As if you don't shove your tongue down every girl's throat within a ten mile radius."

"Thanks for noticing," he said dryly.

"How could I not? I have eyes…unfortunately."

"Um, guys," Sam finally interjected, "Is there a problem?"

"Is there a problem? Is there problem?" Derek was standing now, his face red as he stared down at the two, "Well, for starters, you playing tonsil hockey with my step-sister is a little bit of a 'problem', yes."

"Derek, chill," Sam pleaded, looking around at the growing crowd of spectators.

"No, you chill. You're the one who broke the male code."

"You made that up!" Sam shot back, now riled as he stood at the table across from him.

"Only because I didn't want you to go after Casey."

Sam rolled his eyes. "That doesn't even make sense."

"It didn't have to make sense. You knew it pissed me off, so you should have backed off."

"Um, hello, I'm sitting right here," Casey interjected.

"Stay out of it," the two males said in unison.

"You just have to have everything your way, don't you, Derek?"

"And, you just had to choose Casey out of all the girls in this school. That's lame man. Really lame."

"I'm lame?" Sam countered, "You're the one acting like a five-year-old because I made out with your sister-"

Derek pounced on him before he could even get the last word out, knocking him to the ground beside the table. Casey's eyes widened in horror as they pummeled each other.

"Derek, stop!" she shouted as he planted a mean punch in Sam's face.

But, just as soon as he gained the upper-hand, Sam punched him in the gut. "Sam!"

"What's going on here?" The monitor called, pushing through the crowd.

The boys finally pulled apart from each other, straightening their close as they faced him. The monitor glared at the two for a moment before barking, "Both of you. The principal's office. Now!"

"A fight, Derek? During school?" Nora looked exasperated as she faced the teen in the living room, "You've done a lot things this year, but this is unacceptable."

"You can't treat the cafeteria like the hockey rink," George added.

Nora huffed. "You won't even being seeing a hockey rink until you serve your time in detention."

"But, Dad," Derek turned to George, pleading.

George just simply shook his head, sighing. "I'm sorry, Derek. You've crossed a line this time and you have to pay the consequences. You're grounded for the next week. No hockey, no dates, nothing."

"Oh, come on…"

"You're not charming you're way out of this, Derek," George persisted, "Now, go to your room until dinner."

Derek exhaled deeply, his shoulder slumping and he trudged up the steps. When he glanced over his shoulder to find no pity from his parents, he rolled his eyes and hurried to his room. They really were serious. This was going to be hell. And speaking of hell…

"I can't believe you, Derek."

Derek started, caught off as he regarded Casey in his room. He'd opened the door to find her sitting on the edge of his bed, leg bouncing up and down restlessly. At the sound of the door opening, she'd stood abruptly, facing him with unrestrained anger.

After regaining his composure, Derek made a show of looking around the room. "Hmm, I could have sworn this was my room."

"Yeah, and I could have sworn that my love life was my personal business."

"Not when you date my best friend," Derek bit back, all the humor gone from his voice.

"Ugh! You are so annoying," Casey huffed before storming towards his door. But before she left, she said over her shoulder, "I hope Sam kicked your ass."

And, with that the door shut firmly in his face.

Derek couldn't sleep that night. And, after countless hours spent tossing and turning in his bed, he finally headed to the kitchen. He was clad solely in boxers, bed hair, stubble and a frown. He couldn't believe he'd let Casey's words get to him, that he'd let Casey get to him period the last couple of weeks. But, she'd left him angry, confused, and broody. The worst part, was he knew she was right. Knew that he was being irrational about the Sam situation, but it still bothered him to no end. Gnawed at him. The idea of them to together killed him, and it wasn't just because she was his step-sister.

His thoughts were interrupted by the person in question as he stepped into the kitchen. She was standing there, clad in skimpy pajama shorts and tank top eating peanut butter straight from the jar—one of her few messy habits. And, as he watched her, hair messy and falling over her face, face twisted in delight as she licked the sweetness from the spoon he felt an unmistakable feeling in his gut. A longing. And that made him even angrier.

"I see Ms. Piggy's come out to play," he jeered as he crossed his arms and walked further into the kitchen.

Casey jumped, startled, as she turned towards him. When she realized who it was, she promptly frowned and placed the jar back on the counter. "What, publicly humiliating me's not enough. Now you're stalking me, too?"

"It's called living in the same house," he returned, slightly defensive that she may have caught him staring.

Casey huffed, already visibly agitated as she regarded him. "You are such an ass, Derek."

"Oh, feisty," he snarked, brushing past her to grab a cup.

Casey fought to ignore the shiver the contact created and followed him with glaring eyes. "Is it your goal to ruin my life, to hurt me?"

Derek felt his heart give a little at the catch her voice, but ignored it when he caught her heated glare. "No, but it seems to be your life mission to mess with mine," he bit back, "Hanging all over Sam like some love-sick puppy."

Casey crossed her arms, cocked a brow, and stepped so close to him their toes were touching. "Jealous?"

"Screw you," he growled.

"I knew it," she said in a low voice.

But, Derek quickly composed himself. "If by jealous you mean disgusted by my desperate skank of a step-sister throwing herself at my best friend, then yeah, I'm insanely jealous."

The air crackled as she slapped him. Hard. She reached up to repeat the action when Derek grabbed her arm. She moved her other hand and he clutched that one, locking her up and pushing her up against he kitchen wall.

"Let go of me," she demanded.

"Stop hitting," he countered.

She moved to knee him and Derek instinctively adjusted. But his foot slipped and the freshly mopped floor and they both tumbled, Derek taking the brunt of the force as Casey collided solidly atop him. She moved to strike him again and Derek quickly flipped them over, pinning her arms roughly above her head.

"God, I hate you," she spat.

"I hate you harder."

There was an intense struggle as they grappled on the floor, all the playfulness and innocence of early wrestling matches gone. This was something much more. Casey grunted when he wouldn't budge and thrust her hips upwards. Derek hissed sharply but didn't let her go.

"Apologize," he demanded, his voice low and dangerous in her ear.

"You apologize," she countered.

Their eyes locked in a cold, stubborn gaze, neither willing to relent. Fed up, Casey tried to use her legs, wrapping them around his waist and bucking, trying to escape his hold. Derek's eyes darkened darker than she'd ever seen them as their eyes locked again.

"Stop it," he ordered, his voice thick.


Derek increased the pressure of his hold, and Casey responded with a raw, instinctive move, biting down hard on his neck.

Derek growled, a sharp mix of pain and pleasure spreading through his body. His hips thrust involuntarily and Casey gasped, her mouth releasing at the sudden, unexpected pleasure it sent through her. Suddenly she was aware of everything. How close their bodies were, how her chest felt pressed up against his, the way her legs tangled about his waist. She looked up into his eyes, heavy with unrestrained emotion and lust, and before she could react, his lips crashed into hers rough and unyielding. She moaned into his mouth, her lips parting instantly as his tongue invaded her mouth. Months upon months ofcompetition, angerand frustration, exploded into something else entirely. Something decidedly more pleasurable.

And the pleasure continued to climb as their tongues dueled and the heat grew between them, each grappling, pulling, pressing, tugging at each other. Casey legs tightened unbearably around him and her hands moved wildly across his back, his shoulders, his arms as they both tried to get impossibly closer. They both were deciding that clothes were no longer a necessary part of the equation when a hesitant voice broke through the darkness.

"Smerek, is that you?"

They flew apart as Marti slowly entered the kitchen, blanky in tact.

"Uh, yeah, it's me," Derek panted, voice heavy and husky.

"I couldn't sleep," she explained, "I went to your room but you weren't there. Then I went to Casey's but she wasn't there either."

The teens eyes met and then darted apart.

"Um, I should uh…"

"Yeah," Casey interjected, "You-you do that."

Casey was a blur of panic and confusion as she rushed up the stairs, and Derek couldn't help but stare after her, even as Marti climbed into his arms.

What the hell was that?