Anthor's Note: This is my first Life With Derek fan fiction. It didn't turn out quite like I wanted- but I tried. Casey and Derek are in 12th grade in this story, and George and Nora are having relationship problems. This is a one shot. Dasey.

Disclaimer: Obviously, I do not own Life with Derek or any of the related characters.

Her alarm clock read 3 AM and so, with a sigh, Casey MacDonald gave up and got out of bed. She had been trying to sleep since 9 o'clock that evening, and was failing miserably. That morning, she had the most ridiculous conversation of her life with Kelsey, one of Derek's bimbos, and now she couldn't stop thinking about what the girl had said. Casey walked around her room, rearranging and organizing all the things she came across, wishing she could do the same with her thoughts.

"You're sleeping with him!" That was how the conversation began; Kelsey had walked up to Casey in homeroom and thrown this accusation at her.

"Sleeping with who?" Casey asked, puzzled. This was the first time Kelsey had ever spoken to Casey, despite being in the same homeroom for the past three years.

"He broke up with me!" Kelsey shouted.

"Who did?" Casey asked.

"Derek!" Kelsey screeched. Casey was starting to think it was probably a very good thing she had very spoken to Kelsey before-honestly; Marti made more sense than this girl. Casey blinked-

"And?" she asked.

"And you're sleeping with him!" Kelsey said.

"You think I'm sleeping with… Derek?" Casey asked. This was becoming ridiculous. Derek went through girls so fast that Casey hadn't even know he was dating Kelsey-and now the girl was standing in front of her, convinced Casey was responsible for their break-up.

"No" Kelsey corrected, taking a step closer to Casey so that she was in her face as she said, "I know you're sleeping with him."

"Kelsey" Casey said, trying to be patient, "Derek is my step-brother-"

"Oh please!" Kelsey cut her off, "You were like, 15, when your parent's got married, and they fight all the time. Derek's dad is 'away on business' more than he's home- soon they'll be divorced and you and Derek won't have to hide your dirty little love affair any longer!" Kelsey spat, looking more enraged by the second.

"I'm confused, what would make you think Derek and I were having a 'dirty little affair'?" Casey questioned. There was no point in denying what Kelsey had said about her mom and George, she couldn't remember the last time George had been home for more than a week, and his claims of "business meetings" weren't fooling anyone. Not that Casey's mom seemed to care much. They probably were heading for divorce, but given their romantic track records, this didn't surprise Casey much. It surprised her that Derek had confessed all this to Kelsey, but perhaps she had heard one of their fights from Derek's bedroom and asked about it.

"Derek made it pretty obvious" Kelsey said, "You're not fooling anyone Casey." With that she walked back to her friends, leaving Casey stunned.

Hours later, Casey was still trying to figure the conversation out. Why had Derek made something that wasn't true "obvious"? Derek was a great liar, he could convince you the sky was polka-dotted if he wanted to, but why in the world would he have wanted Kelsey to think he was sleeping with Casey? She wasn't now, nor had she ever, slept with anyone, let alone Derek. It just didn't make sense. Casey went to her desk and pulled out her university acceptance letters, for the past few weeks they had been her best source of comfort. No matter what she was upset about, rereading the letters reminded her that all her hard work had paid off, and that she only had to make it through these last few months of grade 12, and she be out of high school, and out of her house. Casey felt calmer after her letter rereading, so she climbed back in bed, and attempted to get some sleep.

Three days later, Casey sat in the kitchen staring blankly at the snack she had fixed herself, when Derek walked in.

"Careful Casey" he said pointing at her ice cream dish, "too much of that and you'll have even less dates than you do now" He grinned mockingly. Casey just glared at him, and then returned to staring at her ice cream.

"That's all I get?" He asked, "A glare? No come back? What is up with you? You've been weird all week."

"I'm mad at you" she said simply. He laughed,

"How does that make this week any different from any other week?" He asked, smirking at her. Casey stood up, deciding she didn't want her ice cream after all, and walked over to the sink,

"Because I don't have to talk to your bimbo's every week- thank God" She said, putting her bowl in the dishwasher and starting to walk about of the room.

"What?" Derek asked, his smirk slipping a little.

"Kelsey" she said, "Informed me earlier this week that its my fault you dumped her. Is it too much to ask that you keep them away from me?" Casey asked, and then retreated up the stairs to her room. Derek followed her.

"What exactly did Kelsey say to you?" he asked.

"She seems to think that we're having a 'dirty little affair.' Apparently you made it obvious that you and I are sleeping together, so thus, its my fault you dumped her." Casey found it impossible to look at Derek while she said this.

"Shit" Derek said, looking slightly ill and holding on to Casey's door frame for support. "Is that all she said?" Casey looked up at him,

"Yes, that's pretty much it- oh and that since our parents fight all the time anyway so we're not really step-siblings, and they when they divorce you and I will be thrilled. Or something like that" Casey said. "What did you say to her Derek?"

"Is she going to tell other people this?" Derek asked, ignoring Casey's question.

"I don't know Derek- why does it matter? Its not like anyone would take her seriously" Casey said. Derek let out a bitter laugh at her last words.

"Yeah," he said, "they would."

"What?" she asked alarmed. Derek walked over and sat down next to her on her bed.

"Casey, don't you know what people say about us? They've been talking about us for years. People love a good scandal, and-"

"Wait" Casey said, cutting him off, "You're saying that this whole you and me 'dirty little affair' thing is a common perception?"

"Yeah." he said, locking his eyes on hers

"Wh-" Casey began then stopped herself. It was a foolish question. Casey knew why. In that moment, all the things she had been avoiding thinking about for three years came together in her mind to form a very clear answer. All of the little impulses and desires she had pushed away over the years because he was her step brother re-emerged, and she for once, she accepted them. Looking into Derek's eyes, Casey knew he was thinking the same thing and in that moment, everything between them changed. All of the aggression and hostility of the passed three years was gone, and behind that, was what had been there all along; lust, desire, attraction and passion.

"Ok" she said finally, "So if everyone knows why does it matter what Kelsey says? What did you say to her Derek? To make it so obvious?" Casey asked. Derek took a deep breath, and with a sheepish grin on his face he admitted,

"I said your name- when I was hooking up with her, I called your name." He smirked, and Casey laughed,

"I always thought you were smoother than that Derek," she said.

"Even the best of us slip up sometimes" Derek said, and then, leaning over, he kissed her. And Casey, before the ability and desire to think about anything but Derek's lips escaped her completely, decided that her conversation with Kelsey was not ridiculous at all. She would have to thank that girl in the morning.