Author's Note: New fic by me that I hope you all enjoy! I may up the rating in later chapters so make sure you don't have the "filter out M-rated stories" function on! Please review!

Casey shifted in her seat uncomfortably as her blue eyes were trained on the sheet of paper she was holding in front of her. She scanned the note, reading it over and over again until Derek was sure that she had whatever it was memorized.

He figured it was something for school at first, but the look on her face—that pale, ghostly look that had washed over her pretty features—clued him in on that it had nothing to do with homework. Finally she looked up from the paper, her fingers clutching it so hard that her knuckles had turned as white as her face. Derek hoped to catch her eye, but Casey's dilated pupils were glazed over as she stared at a blank spot on the wall next to him, her mind in another place entirely.

Not wanting to seem like he cared, Derek stopped the inquiry from rolling off of his tongue. He pursed his lips together and went back to the game of Scrabble that he was currently in the middle of.

"Casey, it's your turn," Lizzie said without looking up at her older sister. If she had, she would have known that something was wrong.

"I, uh," Casey stood up awkwardly, nearly tripping from how wobbly her legs had gotten, "I gotta go finish some homework," she told them. Her voice was off, as if she was covering some emotion with an un-Casey-like "everything's cool" tone. She quickly turned on her heel and advanced the staircase like she was being timed.

"It's Friday night," Edwin pointed out, shaking his head in dismay at his eldest stepsister. Everyone in the house—hell, everyone in the town district knew that Casey was a bit obsessive about her grades and her schoolwork. A Teacher's Pet. A Grade-Grubber. But doing homework on the Friday night of a long-weekend? That was a little too much, even for Casey MacDonald.

Derek was about to make some snide comment about this, but he looked up to see that Casey had already bolted up the carpeted stairs, out of sight.

Having a girl his age living in the same house as him was strange for Derek. At first, he had been a bit ticked off that he had to share his space with random people—his dad's random new wife and her two random daughters—but the past few months hadn't been as bad as he had imagined. With Casey in his life practically every moment of the day, things were different, yes; but not all bad.

She was a spitfire. A fiery little thing who wasn't about to let Derek get whatever he want, whenever he wanted it. She defied sacred Venturi Rules such as sitting on "Derek's Recliner" (she could sit wherever she felt like sitting!) and always allowing Derek to watch what he wanted on TV (figure skating is way more skilful than hockey anyway!). She fought tooth-and-nail with him at any chance she had to prove that he was NOT the ruler of the house anymore. And she would NOT back down from a fight.

Although Derek seemed so exasperated to have Casey standing up to him and arguing with him over every little damn thing, the truth was that Derek was quite thrilled about it. Finally, someone who he could butt heads with. Someone who wouldn't back down and made him fight to get his way. An exciting challenge to get his blood flowing and his adrenaline going.

He would never admit it, but he was glad that the MacDonalds had moved in. Including Casey.

"I guess we'll skip Casey then," Edwin shrugged, breaking Derek out of his thoughts. Scratching his messy dark hair, he looked over at Lizzie. "Lizzie, you're up."

Derek didn't know much about Lizzie, the younger stepsister. She seemed more quiet, but at times, had been proven to show that she was every bit as defiant as her older sister. She stood up for what she thought was right, even if that meant going up to Derek and persuading him to see things in a different way—a more Casey way. And usually, to Derek's disgruntlement, she was right.

The one thing for Derek that really stood out about Lizzie was the way she was with Edwin.

Edwin, Derek's younger brother who was often forced way out of the lime-light as the middle child by his older brother and his little sister. He had been more reserved and painfully anti-social before the MacDonalds arrived. Derek could remember not seeing him for hours as he locked himself up in his bedroom, playing computer games or who-knows-what. Star Wars figurines or something like that. His door was always shut; stating clearly that he did not want any visitors.

Nowadays, Edwin always seemed to be around—out in the backyard playing soccer, playing board games in the family room, talking, laughing, and never in his bedroom. Always with friends. Always with Lizzie.

And his bedroom door was always wide open.

George Venturi, Derek's scatterbrained father, had changed a lot too since the MacDonald Family had moved in. Sure, he was still as absentminded as always, forgetting to pick his kids up and leaving dairy products out of the fridge until the kitchen began to smell kinda funky. But he didn't work as much. He made it home for dinner practically every night. Always with a smile on his face for his new wife and their family.

The only one that hadn't seemed to change much was Marti—the family member Derek was most partial towards. At only six, the world was still this fun adventure for her. Everything interested her. She always wanted to know "why" and "how." She had imaginary friends and pretended that she was a cat most of the time. Her childish innocence charmed Derek The Charmer. There would always be a special place in his heart for his little sister, this he knew.

Marti had adjusted to the Big Move-In with ease, unlike the rest of the family. For months, Derek had thought that his life was taking a downward plunge into a hellish hole, now that he had three girls telling him and his family how to live. But recently—just recently—he was beginning to see that maybe it wasn't so bad.

"Casey?" Nora asked as she walked into the family room. Lizzie and Edwin both looked up at her expectantly, and Derek scrubbed his face in his hands, coming out of his reverie.

Nora's cobalt-blue eyes, which both of her daughters had inherited, scanned the room. "Where's Casey?"

"Upstairs," Derek answered, noting that Nora wasn't just asking casually for her daughter. Something was up. "Why?" he asked nosily, trying to play it off as if he didn't really care that much.

But his question was lost to Nora, who was already bounding up the stairs for her eldest.

Lizzie, realizing that something was going on, ran up after her mother. Derek was about to run up to eavesdrop when his father walked into the family room from the kitchen.

"Derek," he said in a warning tone, knowing exactly where his eldest son was heading.

"I was just going to grab a CD," Derek shrugged a lie, heading back down the two steps he had gotten up before being caught.

"This is a MacDonald Family moment only," George said wisely, sitting down on the couch where Edwin has scooted up to lounge on while he waited for Lizzie.

"Huh?" Edwin asked, scrunching up his face. "What is that supposed to mean? I thought we were, like, supposed to be one big family now." Edwin's large brown eyes studied his father from the side.

"Yeah, that's true," George said slowly, knowing that Edwin was right. "But, uh… this is something that Nora and the girls need to talk about together."

Now Derek was intrigued. This had to be something juicy. "What is it?"

"It's not our business," George held up his hands so Derek wouldn't bother interrogating him. He wasn't going to give out any information and that was final.

"I have to take a leak," Derek blurted quickly, moving back over to the banister.

"Derek," George warned, giving him the sharp Parental Eyebrow Arch.

"What, do you want me to pee in my pants?" Derek shot back.

Sighing, George gave up, waving his son off. Derek jogged up the stairs and headed right past the bathroom. Casey's bedroom door wasn't open, to his discouragement, but it was left slightly ajar. He pressed his ear against the door experimentally.

Muffled voices.

"….him married…"

"…not only…stepbrothers…"

"…not your…love him…"

"…two of you…weekend?"

Seeing that he was getting nowhere, Derek moved away from the door. And just in time too—the door swung open. A deadpanned Lizzie and a slightly flustered-looking Nora walked out. Neither seemed to notice Derek as they walked by him.

He turned to look through the now-opened door. Casey was sitting there on her bed, looking eerily blank. Numb. Her eyes looked far away and her hands were clutched tightly together in her lap. Slowly she began to sway back and forth, her mouth turning downward as she visibly became upset.

"Case?" Derek asked, stepping in closer, slightly concerned.

Casey immediately snapped out of it, and her eyes turned cold. "What?" she asked in annoyance.

Derek knew when to back off. Slowly he stepped back again as Casey shot daggers out of her eyes. "Nothing," he said slowly.

"Then get out," Casey looked un-amused. She got up, walked across the room, and slammed the door shut in Derek's face.

Not very unlike Casey, who pissed off easily. Giving up, he stalked over towards his bedroom.

"Kids, dinner!" Nora shouted just as he sat down at his computer to see who was online. He wanted to ask Sam over for dinner, but realized it was a bit late to do that. Turning his monitor back off, he stood up, stretching the kinks out of his back so graciously given to him from hockey practice earlier that day.

"I'm not hungry!" he heard Casey yell as he walked out of his bedroom.

"Casey, now!" Nora shouted back in agitation.

Casey let out an annoyed heavy sigh and charged out of her bedroom, practically bombing into Derek. He instinctively grabbed her to steady her, catching her just before she tumbled onto the hardwood floor.

Both of them looked down at his hands wrapped securely around her waist. This strange feeling washed over Derek, causing him to pause. But that moment didn't last because as soon as Casey got upright, she shoved his hands off of her, eyes blazing.

"Don't. Touch. Me," she growled before pushing past him.

Derek's tawny eyes narrowed as he watched his stepsister's retreating back. Sure, she was a feisty girl. But she was never this… bitchy.

What the hell was up with Casey MacDonald?