Classes ended and exams started, yet despite a rigorous study schedule Derek set his plan into motion. It just so happened that he shared a class with that Bell guy, the one Casey had destroyed at beer pong, and Derek had it on good authority that Casey might have a thing for him. So he set up a study group at their place with Bell and a couple other people, planned to share a few handy hints for picking Casey up, and sit back and watch her crumble. It was perfect. His buddy Kevin showed up first and they got to work in the living room while they waited for Jamie Bell to arrive. Derek was bent over his cue cards scribbling some notes when Casey came down the stairs.

"Don't mind me."

Derek glanced over and did an honest-to-god double take. Casey was hurrying by in nothing but her underwear. It wasn't any more scandalous than a bikini; perhaps the plain cotton set was even less revealing than what she wore in the summer, but there was something extremely intimate about it. He watched her until she disappeared down the basement steps.

"Dude," Kevin said. "Who was that?" Derek shook his head. "I have no idea," he muttered. The Casey he knew was not the type to prance around in front of strangers in her underwear. It was a ballsy move.

"You don't know?"

"What? No, forget about it. She's off-limits."

Casey came back up toting a full laundry basket and this time, thankfully, she was dressed. "How's the studying going?" she asked cheerfully. Derek glared, Kevin grinned hopefully. "Great, want to join us?"

"Can't, I'm studying for my Econ exam, then I have to work. Thanks though!"

Derek managed to stay in his seat for maybe thirty seconds after she'd gone up the stairs before jumping up after her. She was folding laundry when he burst through the door to her room. "What the hell was that?"

"What the hell was what?" she replied with exaggerated patience.

"That little show you put on just now in your underwear."

She rolled her eyes. "Well excuse me, your Highness. If I want to walk around this house butt naked that's my choice, but as it happens my clothes were in the wash and I didn't expect anyone to be downstairs. I'm so sorry I offended your delicate sensibilities." Her tone dripped sarcasm and defiance, and after a moment he couldn't help himself from sauntering over to her and giving her a slow, deliberate once-over. "I'm sure I'll survive. Kevin not so much. That's a cute little bra you've got, by the way." She raised a brow. "I thought your only concern with bras was taking them off."

Don't tempt me. She was too close all of a sudden. They were standing only inches apart and the energy between them had taken on a different life. He could feel it, and by the way her pupils dilated, she noticed it too. For a split second he wanted to dig his fingers into her hair and yank her against him. His blood was pumping and her eyes dropped to his mouth, and then-

The doorbell rang.

Oh, thank god.

Casey waited until Derek had disappeared out the door before exhaling heavily. Her heart was still pounding. If that doorbell hadn't rung what would have happened? He wanted to kiss her, she was almost sure of it. Finally she let herself smile. It was working! She'd been fully aware that Derek would be there when she'd worn her underwear around the house. She hadn't expected it to work, not really, but he'd taken the bait magnificently. She'd gotten the idea the other night after the party, when he'd looked at her that way in his room. Obviously he was on the brink of failure when he started seeing her as attractive, so she'd decided to help him over the edge. It might require some tasteless personal sacrifice, but all was fair in love and war, right? Never mind that just now she'd nearly quivered with the need for him to kiss her. And then there was that time in the kitchen when he'd touched her and her legs had gone weak. She wasn't too proud to admit she wasn't impervious to the tension that had sprung up between them all of a sudden, she was just confident enough that he would succumb first.

It was after one in the morning when Derek got off work, and he tried to be quiet as he made his way up the stairs. The consideration turned out to be pointless as Lisa's door was open and her room empty, and the light was blazing in Casey's. He peered around the door frame to say good night and saw her pacing with a handful of multi-coloured cards and the manic look she used to get in high school at exam time. "Casey," he said slowly, approaching her as carefully as he would a wild cat. "How long have you been studying?" She didn't acknowledge him, but in this instance he figured she was so focused that she hadn't heard him. He strode across the room and grabbed the notes from her hand.

"Hey!" she said indignantly. "What are you doing? Give those back!"

He ignored the demand. "Casey, how long have you been studying?"

"I don't know, a few hours. Since lunch. Give them back, I have to review for my exam tomorrow!" Derek sighed and stuffed the notes in his pocket. "Case, it's nearly two. In the morning," he stressed. "You've studied enough. You know everything and you're not going to fail. Say it with me." She glared but grumbled the mantra he'd developed for her years ago. "Fine. I'm not going to fail."

"Good girl," he said and reached up to knead her shoulders. "Christ, you're like a plank of wood," he muttered. "You really need to learn how to relax, Space." Even as he said it he could feel the tension seep out of her as she leaned into him just a little. He caught sight of their reflection in the mirror on her closet door: her eyes were closed and she was almost smiling, and he looked like the devil on her shoulder. He caught his own eyes in the mirror and grinned – why waste such a golden opportunity? As he massaged the muscles at the base of her neck he couldn't help but wonder just how sensitive she was, so he abandoned the massage to lightly trail his fingers down the side of her neck. He glanced back to the mirror to gauge her reaction and found her watching him with an unreadable look in her eyes. He didn't tear his eyes from hers as he slowly skimmed his hands across her shoulders and down her arms, over her hips and her stomach, and it was only as his thumbs grazed the sides of her breasts did she reach up to grasp his hands. "I should get some sleep," she said quietly. He held her gaze for a moment longer before turning wordlessly to go back to his own room. Like he was going to sleep after that.

Derek got up at noon after tossing and turning restlessly for hours, and by then Casey had already finished writing her exam. He was in a foul mood and was itching for a fight. He eventually found Casey outside shoveling the sidewalk and he scowled when she started clearing their elderly neighbour's driveway. Saint Casey, he thought with a sneer, not feeling charitable enough to admit he would have done the same for the old lady. Impulsively he put on his jacket and threw open the door to grab a handful of snow off the railing and launch it at her. His aim was on the mark.

"Der-ek!" Casey dropped the shovel and dug the snowball out of the collar of her jacket. He grinned maliciously and threw another one. "Oh my god, are you a child?" Casey shrieked, but it was enough to get her to heave one back. He didn't bother to duck – he knew what her aim was like, so he was greatly surprised when he got a mouthful of snow. Casey nearly collapsed in a fit of giggles.

Just like when they'd fought over batteries in the living room, he jumped the steps and ran to tackle her to the ground. This time he was successful, mostly because she was doubled over laughing, but despite that she managed to get another handful of snow as they hit the ground and stuffed it down the front of his shirt. He hissed as the ice cold hit his skin and tried to pin her down to return the favour, but she wriggled out of his grasp. They wrestled around a bit, culminating with Casey sitting on him, a triumphant gleam in her eyes. "Ha!"

Derek was suddenly reminded of the very different kind of look she'd given him the night before, and that memory combined with the way she was straddling him now was about to result in a rather awkward situation. Fortunately he had plenty of experience in this particular arena and quickly and expertly flipped her onto her back. She smirked up at him. "You've done that a few times, huh?"

Apparently they weren't going to acknowledge what had happened the night before, and that was fine with him. He was content with fighting with her if nothing else. "Probably as often as you've wound up on your back." She got that indignant look that usually meant a lecture was imminent, but he was saved when their neighbour poked her head out the door. "Hey you two, when you're done fooling around come on over for some hot chocolate!"

Casey didn't take her eyes off his. "Thanks Roberta, that sounds great!" she called, but he was distracted by the way she'd slid her knee between his legs. Distracted, but not stupid, and he rolled off of her just as she was about to bring her knee up sharply into his crotch. "Careful Princess," he warned lowly. "I didn't take you for suicidal." Casey stuck out her tongue, pelted him with one last snowball, and high-tailed it over to Roberta's.

This was turning into a disaster of epic proportions. Casey scowled into her mug as Derek shamelessly flirted with Roberta and for the umpteenth time in the past few days, she tried to figure out where she'd gone wrong. It was all Derek's fault, that much was obvious. If he wasn't so damned stubborn and had screwed up weeks ago like he was supposed to, neither of them would be in this mess. She hated to admit it but her plan wasn't working out how she'd hoped. She wasn't an idiot, she knew she was getting to him in a big way, but the problem was she wasn't so sure of her motivation anymore. Since when did trying to get Derek to lose a bet involve letting him run his hands all over her?

Since when did she want him to?

That thought hit her like a freight train and she wanted to bury her face in her hands, but contented herself with glaring daggers at Derek's back. Her anger wasn't enough, however, to drag her mind away from what just a whisper of a touch from him had felt like, and then what it might have been like if she hadn't stopped him…

She got lost in the fantasy for a moment and was rewarded with an elbow to her ribs. "Earth to Spacey," Derek said snidely, and Casey couldn't fight the blush that crawled into her cheeks. She tried to ignore him and shrugged apologetically to Roberta. "Sorry, I was just thinking about my exam this morning."

"I'm sure you did just fine, Dear," Roberta said kindly. "I was asking if you're looking forward to your vacation back home. You leave in a few days, don't you?"

"Yeah, Friday." She hadn't realized it, but Friday was only four days away. They had never set any real parameters around their bet, but something in Casey was determined to have this game resolved before the drive back to London. That meant she had four days to either break Derek or get him to agree to a truce, and honestly she wasn't sure she had what it would take to accomplish either. Breaking him technically meant he'd have to hook up with another girl and suddenly that didn't seem like such a great idea. Casey could barely stop her jaw dropping at the thought. God, was she jealous of some faceless girl that Derek had yet to meet?

The thought made her stomach turn and she frowned uneasily. "I'm sorry, Roberta, I have to go. I'm suddenly not feeling well." She refused to meet Derek's eye as she pulled on her jacket and hurried out the door. By the time she made it across the lawn to her own place she was ready to throw in the towel. Nothing was worth being jealous of a Derek Venturi conquest.

"Hey Case," Lisa said cheerfully, then caught sight of Casey's expression. "What's wrong?"

"I give up, that's what. I can't do this anymore! He can have it."

"Casey, no!" Lisa admonished and led her to the couch. "You can't let him win just because you're horny." Casey snorted and rolled her eyes. "Please give me a little more credit than that. It's just…I'm tired of this stupid game. I want to go home for Christmas with nothing to worry about but eating too much turkey or whatever." She huffed and scowled at Derek's hockey bag, which was sitting by the door, ready for his afternoon game. She didn't notice the shrewd look Lisa gave her. "Look, Casey, I will not let you give up now. You've got this in the bag! I mean, he even looks at you like he wants to devour you half the time."

"What?" Casey screeched. It was worse than she'd imagined if even Lisa could see it.

"I just mean that if he's desperate enough to want to hump his own sister-"

"Step. And that's disgusting."

"Same difference. All you have to do is just nudge him in the right direction, you know? Take advantage of the situation."

Casey scowled. Hadn't she been doing that already? "And what would you have me do?" she asked peevishly. Lisa shrugged. "I'm sure you can think of something. Let him see you naked by accident. It doesn't really matter, I just don't want to see you lose. I've seen him hold things over your head from when you were in high school – he would never let you forget this."

Well she was right about that, Casey mused. In fact it was the only reason she could use to justify not giving up. Don't forget about all the things you wanted him to do last night…her traitorous mind whispered. She glared at the thought and pushed it aside. She was stronger than this, damn it! And, really, this attraction to Derek wasn't all that surprising as he was the only male she had access to on a regular basis who she was actively trying to seduce without actually seducing. "I'm so confused!" she wailed miserably.

"Casey, relax," Lisa soothed. "You have to admit you've been having fun with this bet. Watching him squirm every time a girl walks by is really entertaining."

"I guess…" Casey sighed. "Fine, but if this isn't resolved by Friday, I really will give up."

She was still on the couch contemplating her conversation with Lisa when Derek came in. "What's up with you?" he demanded, pausing at the foot of the stairs. She snorted inwardly – like he didn't know. "I'm sick," she muttered. "In the head."

"What?"

She rolled her eyes, suddenly tired of him and anything related to this game for the moment. "Nothing. Aren't you going to be late for hockey?" He gave her a funny look, then shook his head and went up the stairs. She watched him go and decided a little exercise wasn't such a bad idea. Going for a run might clear her head some, and it did, when she got out there. She focused on the biting cold on her cheeks and the crunching snow under her feet, and ran as far as she could. She wasn't headed in any particular direction, but when she passed by the arena where Derek was playing his game, she wondered what her subconscious was telling her.

"Casey!" It was Danielle, from her economics class, and a blonde girl near the entrance. Since her lungs were burning anyway she stopped to say hello. "What're you two doing here?" Danielle shrugged. "Watching the game. One of my friends is playing and he badgered us into coming." She paused. "I didn't take you for a runner."

Casey shook her head. "I'm not, I just have a lot on my mind." Danielle nodded wisely. "That thing with Derek still going on?" The look on Casey's face must've given her away because Danielle laughed. "Poor you."

"What thing?" the other girl asked, suddenly interested in the conversation. Danielle introduced them. "Casey, this is Kate."

"Hi." She paused and sighed. "I have this bet with my…roommate –" Friends wasn't really accurate and to call him her step-brother after all that had happened lately made her feel dirty in a bad way. She outlined the basic parameters of the game and watched Kate's brows inch higher and higher. "Wait…" she said slowly. "You don't mean Derek Venturi, do you?"

Casey sighed. Of course. "Uh huh."

"He's playing today. He's pretty hot."

The cold was starting to seep in, now that she wasn't moving. She bounced from foot to foot. "Ah, I guess," she said half-heartedly, trying to pretend she'd never noticed – which, to be fair, she never had until recently.

"You know," Kate said thoughtfully. "I could help you out, I think." Casey exchanged a glance with Danielle, who shrugged. "How?"

"I was planning on inviting him out after the game anyway, and after that, well…" she trailed off, but had that smile that only the most confident girls got in situations like this. Kind of like Kendra, Derek's old girlfriend.

"I –" she hesitated. What are you doing? This is what you've been waiting for! "Um, ok. Yes." She slapped on a grin. "That would be awesome, actually!" Kate looked smug and Casey had the fleeting thought that this girl was trouble with a capital T, but that wasn't really her problem. "I mean, only if you want to."

"Oh, I want to," Kate assured her. "We'd better get back in there though. Danielle can tell you all about it later!" Danielle looked kind of taken aback by the sudden development and offered Casey a feeble wave as she followed Kate back inside. Casey stood there for a moment, one hand pressed to her stomach. She felt kind of sick at the thought of blonde, man-eating Kate getting her hands on Derek. Not because she was worried about him, but because Kate was just the kind of girl he'd go for. Unbidden, the image of Derek putting his hands on that girl the way he had to her the other night sprang to mind and jealousy bubbled up in her chest.

"Oh god," she groaned. Screw the run, she thought. I want a drink.