On her way downstairs, she tiredly walks past his room, noticing how oddly quiet he was being for someone of his manners. She steps back and peers in nosily, and sees him sprawled out across the bed in an X. His eyes are closed and she enters.

"Did I invite you in?" he asks sardonically, unmoving.

She rolls her eyes, though she knows he doesn't see it. "I just came to see if you're okay. You seem kind of down."

"I'm fine," he deadpans.

"Obviously you're not," she replies, irritated by his tone. She steps in farther and crosses her arm. "Is this about Sally?" Even after all this time, she knew he was still upset about his ex moving to the other side of the country.

"No," he answers. "And if it was, I sure as well wouldn't want to talk to you about it."

She quickly closes the door. "Derek," she chastises. "Watch your language. Marti picks up everything."

He groans and covers his eyes with one arm. "Whatever."

She decides to sit on the bed, approaching a dangerous closeness to him. He moves slightly. "Derek, it's okay to be upset about Sally."

He jumps up angrily and shouts, "I'm not upset. Goddammit," he bellows. "Can I not be in my room in peace?"

She stands up, too, pissed at his tone. "Don't pretend you're not a little upset about her leaving. Jesus, Derek, Edwin is upset about her leaving. Grow a pair and admit you're feeling something."

He inches closer to her. "She was just a girl. And she left. Why should I care?"

She steps closer too. "You should care because she made you feel. She made you happy." She angrily whispers her next words. "Without her, you're just an arrogant fucking jerk who pretends to feel nothing about anything unless satisfaction in making my life a living hell." She steps back, her heart beating rapidly. "Talking to you is a waste of time. If you want to be a robot then be one."

"Don't talk down to me like you're the queen at dealing with your emotions," he spews at her. "All you do is sit and mope about Max. I'd rather sit in here and do nothing than be like you, annoying everyone in a ten mile radius of your fucking bedroom. I'm not going to cry like a baby. I'd be surprised to see you ever kiss a guy again."

She glares back at him."I have nothing to prove to you. And with the way you deal with your emotions, I'd bet you don't kiss another girl in high school."

"Oh really?" he says, sizing her up.

"Really." Their faces are inches apart.

And in that split second, he breaks the space between them and places his lips on hers in a relatively violent manner, rising a surprised, "oomph!" from Casey. She falls back momentarily, but they never break. They stand there, their lips locked. His tongue rolls over her bottom lip in an effort for her to open her mouth slightly, and she does eagerly.

In the heat of the moment she brings her arms up to grip his biceps, and he lifts her up, effortlessly wrapping her legs around his waist. Derek walks steadily over to his bed and lays her down on her back. He hovers over her body for a moment longer and never breaks the kiss when he finds a comfortable position in his endeavours.

Needless to say they weren't really thinking straight, but at the moment, who cares, right?

He wordlessly lifts her shirt up a little to graze her stomach with the tips of his fingers and she writhes involuntarily at the touch. He chuckles. She pulls his head down to her neck and he responds by kissing there instead and she does everything in her power not to gasp. He pulls the shoulder of her t-shirt down, then brings the strap of her bra down with it, switching shoulders. He starts to bite the crook between her collar bone and her ear and she pushes him away slightly, sitting up.

He looks at her, first in surprise, then confusion, as he thought she was enjoying it. "Wha-" he's cut off by her lips trapping his once more. She quickly manages to turn the tables, and she's on top of him, her knees hugging his waist. She bends down and her hair falls to curtain their faces from the door inadvertently. She grins and he pulls her closer, her chest pressing against his.

She stops suddenly and starts to giggle, despite herself. She covers her mouth with her hand awkwardly, trying to control her laughter.

"What?" Derek asks, unsure.

"What are you doing?" she asks between fits of uncontainable laughs.

"Nothing?" he wonders. He tries to pull her back down.

"Well, um," she replies, looking beneath herself.

His eyes widen, first in embarrassment, then in smugness. He pulls her waist down on himself further. "Do you want to take care of it?" he teases.

She shoots him a look and moves on his legs to get a better chance at accessing his... assets. She's mid unbuckle of his belt and there's an unwelcome noise from outside his room.

"Derek?" George calls, knocking lightly. "Are you in there?"

Both Casey and Derek's eyes widen, horror plastered across their faces. She jumps quietly from the bed and fixes her hair and clothes to perfection and sits on his chair, grabbing the nearest magazine and opening it to a random page. Derek leans forward and lays on his stomach, concealing his semi-buckled belt and the hardening of other things.

George enters as Derek calls to respond, "yeah," in the most indifferent tone he muster.

"Casey?" he says, confused. "What are you doing in here?"

She gives him a dry look. "I'm trying to educate Derek on why these magazines are made for chauvinistic men to objectify women," she explains. "He's not getting it." She rolls her eyes.

"What I'm not getting is why it matters to you what I look at in magazines," Derek counters.

George raises his hands defensively. "Sorry I asked. Why was the door closed?"

"You know Derek and his mouth. It's not late enough for Marti to be in bed yet so I tried to keep the noise pollution to a minimum." Casey smirks and Derek scoffs.

"What your language you two," George says. "I came up here to see if you guys want to come with the rest of us to Smelly Nellie's. I forgot it was my turn to do groceries."

"Go out in public," Derek summarizes. "With you guys. I'll pass."

Casey rolls her eyes. "Don't be rude. I would come, George, but I do have a bunch of homework tonight. This evident waste of time wasn't on my schedule but I'll have to work around it. I'll just make something quick later tonight."

He nods. "Okay, no problem. Derek, don't bother Casey. See you later."

As George is leaving, Derek gives her a look. She understands though, and pipes up. "Wait," she says. "How long do you think you'll be?"

"I don't know, two hours or so. Why?" George asks.

"I was thinking I would go with you, actually," she explains. "But never mind."

George nods and leaves, Casey following suit, making a b-line to her bedroom. "Bye," Nora calls from downstairs.

"Bye, mom!"

Within five minutes, the family and the car is long gone. Casey is in her room, writing away at her homework – incidentally, she did actually have homework – when Derek walks in.

She pays him no attention, but he sits on her bed. "I was thinking," he says. "You never did take care of my little... problem."

She stops writing and turns around, facing his devilish smile. "Derek, I'm not taking care of your problem. We shouldn't have done that. We're brother and sister. It's wrong."

"Case," Derek reasons. "We're not actually related. There's nothing in the Declaration of Independence that says step sibs can't fool around."

"Derek, that's American. We have the Charter," she sighs.

"Whatever. Why can't we do this?" he asks grumpily.

She scoots closer and stares at him. "Does it not bother you?" she asks. He stares at her, dumbfounded. "That you just made out with someone you spend every second trying to abolish? You literally go out of your way to ruin my life. You hate me. We hate each other." She looks away. "I can't believe what we did." She goes to turn around and he stops her.

"Look, Case, I don't care."

"You just want someone to make out with whenever you want."

"Yeah," he shrugs. "But don't you?"

She sighs inwardly. "I guess."

He brings her to her feet. "Then no one has to know." He grins sheepishly and flops down on her bed, letting her fall on top of him. He knocks her books off her bed, earning an annoyed, "De-rek!" from Casey.

And for the next little while, they explore the implications of the little word "step", and how it literally draws the line between legal and illegal. They're just glad they're on the legal side.