A/N: I started this years ago, and come back to it every so often. I have a few chapters to post, and depending on your interest, do hope to finish it. Post Vacation with Derek.

Casey put the finishing touches on her makeup and examined herself critically: hair loose, dress just snug enough to really get his attention. Not bad, she thought, and headed downstairs to meet her date. "How do I look?" Her roommate, Lisa, looked up from the pile of books spread over the dining table. "Hot," she nodded approvingly.

"You look better without all that makeup shit."

Casey turned in disbelief to the couch where Derek was sprawled, a half-empty bag of her chips in his lap, watching a hockey game. "And you look better at your own house," she snapped. "Why are you here?" He didn't take his eyes off the game. "Because it's my mission in life to make you miserable?"

"Mission accomplished. Go home."

"Nah, I'm good here."

Casey yanked on her shoes and shot Lisa a dirty look. "Why did you let him in?"

"Didn't. He was here when I came in."

"Door was open," he said as the game went to intermission and he went to root through the fridge. Casey gaped at him. "Even after all these years your audacity astounds me."

"I thought I left some beer in here last week."

"Oh, that was yours?" Lisa said, but was paid no attention. Derek kicked the door of the fridge shut and dumped the makings of a sandwich on the counter. "There was a minor incident at my place. Figured it was a good idea to clear out for awhile."

"Let me guess, that minor incident involved you and someone's girlfriend."

"She said they were broken up."

Casey rolled her eyes. "You're unbelievable. What about your precious guy code?"


"Duh. Remember that whole thing with Sam?"

"Oh, right. That was about sisters. Mostly I just didn't want you dating my friends."

Casey snorted, but she'd never wanted him dating her friends either so left it alone. Derek took his plate back to the couch, dropping a sandwich in front of Lisa on the way. "So, who's getting lucky tonight?"


"C'mon Case, you've got the slutty shoes on. Usually means you're out to get some."

"Screw you! Seriously, you need to leave. Now."

"Well this sandwich isn't going to eat itself…"

"I love how you manage to ruin my night before it even starts."

"Cry me a river, Princess," he mocked, and turned up the volume as the game resumed. Since he looked like he was settling into the couch for the long haul she grabbed the remote, switched the channel, and pulled the batteries out – something years of experience had taught her. That had him on his feet. "Casey, change it back. Now. This is a crucial game."

She tossed the empty remote at him. "This is me not caring. You could always change it by hand – oh, wait, you can't because you busted the TV last time. Guess you'll have to watch it somewhere else."

"Casey," Derek said dangerously. "Give me those batteries."

"Derek," Casey replied sweetly. "You can kiss my ass."

That was all the invitation he needed to spring over the coffee table and tackle her in an attempt to get them back, but she knew his game and dodged the attack. It didn't take long before they were wrestling over a pair of lousy batteries and Derek hooked her behind the knee with his foot and they toppled to the floor. He was just about to pull her fingers apart when she bit his hand. He let go with a yelp and she used that moment to stuff the batteries down her top. "HA!" she grinned triumphantly. There was one line Derek would never cross with her – her hemline. She could see the indecision written all over his face and used his hesitation to elbow him off of her. It was when she was back on her feet that he blindsided her and stuck his hand right down the front of her dress. "Der-EK!" she shrieked, and in that moment noticed Justin, her date, in the open doorway with Lisa. He didn't look impressed. "Am I interrupting?"

Casey shoved Derek away and barely noticed when he tripped over a cushion and ended up on his ass. "Justin, hi! No, just a minor disagreement. Let me grab my jacket." She went to find her coat in the kitchen and fished the batteries out of her bra on the way. Derek followed.

"You're wearing the fuck-me shoes for that asshole?"

She opened the back door and threw the batteries out into the dark. "Go fetch."

The post-game interviews were still going on when Casey got home. Lisa hadn't moved from the table and Derek was once again sprawled across the couch. She shoved his feet out of the way and collapsed in a huff. He muted the TV. "That was quick."

She pulled off her shoes. "He was an asshole."

"You've gotta stop looking for Prince Charming when you just want to get laid, Spacey."

"You're such a pig. Unlike you I do not consider casual sex a sport."

"Yes you do, you just call it 'dating'."

"Oh, whatever! I'm not going to sit here and let someone who spent an entire year whoring around Europe judge me."

"As opposed to the year you spent whoring around New York?"

"You mother- you know goddamn well-"

Derek held up his hands in surrender. "Don't get your panties in a twist, Princess. All I'm saying is that you aren't really in a position to judge either. How many guys have you been out with since the semester started?" She was fuming but couldn't help but do the math. Derek took her silence as an assent. "That's what I thought." She tried not to pout. "I have no problem being single whereas you get the shakes if you can't feel up some bimbo every other day."

"Well thanks to you I filled my quota tonight," he said nastily.

"You know you're hard up when you cop a feel from your sister," Lisa interjected.

"STEP!" they snapped immediately. Lisa shrugged. "Same difference." But they'd already forgotten her. Casey sneered. "I could outlast you any day of the week." Derek leaned in, eyes narrowed. "Is that a challenge?" They were practically nose-to-nose now. "What do you think?"

"I think you're getting into some dangerous territory."

"Afraid you can't handle it, Der? Because I'm not just talking about sex. I mean no dating, no sex, and nothing in between. You so much as touch a girl, you lose." They stared each other down for a moment, then he got that self-satisfied smirk that she hated so much and leaned back. "This'll be too easy."

"I think you're fooling yourself," Casey said honestly, then turned to Lisa. "You're witness to this. It starts right now."

"I'll make a note of it," was the dry response. Derek got his stuff together and headed for the door. "Oh, Case, we still on for that study session tomorrow night?"

"Yep. I made some extra notes for you."

"Thanks. Lock up behind me, I don't want any weirdos off the street coming in. Night Lisa," he called. "And Casey? Game on."

Lisa looked rather bemused. "I do not get the two of you." Casey was perplexed. "What's to get? Anyway, I'm gonna go run a bath. Night!" Lisa watched Casey head up the stairs and could only shake her head.

The first two weeks were a breeze, but by the third Derek was beginning to lose his resolve. It seemed like every girl on campus knew of his bet with Casey and was crawling out of the woodwork to tempt him. The most startling thing was that this was probably the single most important competition he'd ever had with Casey. Whoever won this one would be the dominant player in their relationship from then on. It was not a challenge he intended on losing. He just needed a good motivator to keep his head in the game. Then, midway through the third week fate intervened. Lisa happened to mention that their third roommate had moved out and there was an available room in their house. This came at the perfect time as the situation with his own roommate's girlfriend had only gotten worse, and it was the perfect way to get under Casey's skin. They hadn't lived under the same roof for four years, but he figured that old habits died hard.

He made a point of moving his stuff in on the night Casey taught her dance class so that he'd have the advantage of surprise. When she came in later that night, he was in his new room doing some work on his laptop. He'd made sure to keep the door wide open as she'd have to pass it to get to her own, and he was not disappointed. He heard her come up the stairs, heard her walk down the hall and pass his door, heard her stop, and only did he look up when she marched through the door.

"What the fuck?"

It was better than he expected. She looked furious and completely confused at the same time, and he always knew he'd got to her when she swore. "Hey Case," he grinned brightly. "Good class tonight?"

"What are you doing?"

"Homework. Why?"

Her nostrils flared and she fisted her hands on her hips, and he nearly laughed aloud. "Ohh, you mean what am I doing here? I'm your new roomie!" Her jaw nearly hit the floor. "Like hell you are."

"What, you think I'd go so far as to move all my stuff in here just for the fun of it?"

"That's exactly what I think. This is just the kind of stupid prank you'd pull."

"Well if you want to call Barry and check, be my guest, but could you do it somewhere else? You're pretty ripe at the moment and I've got to get this paper finished." All she could do was growl in frustration and storm out of the room. "Aw, come on Casey, it's just like old times!" he called after her gleefully. "We're even sharing a wall again!"

Her door slammed so hard that his window rattled.

It was well after midnight that same night when Derek realized there was a minor, unexpected flaw in his plan. He'd gone down to the kitchen for a snack and found the lights blazing, the radio on low, and Casey standing tiptoe on a kitchen chair while she rooted through a top cupboard. "What are you doing?" She jumped, startled, but barely spared him a glance over her shoulder. "Working out my frustration creatively," she said through clenched teeth. He ambled over to the fridge and then noticed that the countertop was covered with dishes and various boxes of food. "You're cleaning."

"Organizing," she said shortly. Derek rolled his eyes. "Your OCD's showing big time, Space." And then he realized that that wasn't all that was showing. She was wearing some flimsy tank top and a ratty pair of shorts; nothing he hadn't seen before, except this was the first time he noticed just how short her shorts were. When she reached up to the highest part of the shelf, those shorts dipped down so low he wondered if she was even wearing underwear. He was immediately mortified at the thought, but was having a very hard time tearing his gaze off of the smooth skin on her abdomen. When those shorts of hers drooped just a little lower to reveal her summer tan line he knew there was no way she was wearing underwear, and he nearly dropped the carton of juice he was drinking from.

And then, when he didn't think it could get any worse, he noticed something else. A few loopy black lines peeked over the very low waistband of those shorts and Derek choked on the orange juice. "Is that a tattoo?" He spluttered after the worst of the coughing had subsided. Before he knew what he was doing, he was reaching out and his fingers brushed her skin, intent on edging down those shorts to get a look at the tattoo that Casey had and never told him about. For a split second – barely a heartbeat – he let his thumb stroke that little bit of skin and watched the goosebumps raise in its wake, then he heard the sharp intake of breath from her and realized what he was doing. He snatched his hand away as if he'd scalded it.

Oh holy fuck. He tried desperately to cover that inexplicable moment in which he'd lost his mind. "You have a tattoo?" he demanded, attempting his usual bravado. He could see the wariness in her eyes, and he hoped to God she would think it was nothing. "Not that it's any of your business," she began stiffly. "But yes."

"What is it?"

She pursed her lips for a moment, then smirked. "That's for me to know." He nearly deflated with relief. He didn't bother with a retort before making a hasty retreat to his room. The flaw in his plan, he acknowledged, was that he was enduring a self-imposed term of abstinence while living in a house with a girl who cleaned the kitchen in the middle of the night in the smallest shorts imaginable, had secret tattoos, and had got goosebumps when he'd touched her. Never mind that that girl was his own step-sister; the same step-sister he'd shared a house with for four years and never so much had an erotic dream about. He'd never before admitted to himself a very unsettling truth: Casey was attractive, and he was in trouble.