A/N: So I wrote another chapter! yay! So I used this one to set up another (a fifth chapter) but I don't know if I'm going to go past that...I might. Um...so Lizzie/Edwin might be a little OOC in theire last convo together, but I always saw them as being way mature for their age. Anyway...ENJOY! Review for me, please and thank you! -Mac

Disclaimer: I don't own. Nuff said.

The Investigation

"I'm telling you there's something up with them."

"I completely agree. What do you think it is?"

"A bet?"

"No. A compromise? Like the Be-Nice Clause?"

A shaken head, "Nah. It's something, something different than anything we've seen before."

"Want to investigate?"

"We're the only ones that pay any attention. I think we're obligated."

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Edwin and Lizzie poked their heads around the corner as they watched Derek and Casey. Derek and Casey had arrived at the bathroom at the exact same time. Edwin and Lizzie were ready for the huge blow out that you would usually see between the two to determine who got it first. But it never came, at least not yet.

"Whatcha doing?" Marti's voice questioned as she popped up beside Lizzie.

"Shhh!" Edwin exclaimed quietly. "Be quiet!"

Marti grinned and repeated herself in a quieter voice. "Whatcha doing?"

"Nothing Marti." Lizzie replied.

"Are you spying on Smerek and Casey again?" Marti asked, tilting her head to the side.

"Observing." Edwin responded.

"Spying." Marti corrected matter-of-factly, nodding her head.

"There's something up with them Marti, we're trying to figure out what." Lizzie said honestly.

"What's wrong with Smerek and Casey?" Marti frowned.

"We don't know Marti, that's what we're watching them for." Edwin sighed, Marti was starting to get frustrating.

"There right there!" Lizzie exclaimed pointing. "Derek just let Casey have the bathroom without a word. He just let her have it."

"Derek's been acting weird like that for months." Edwin responded.

"Casey too." Lizzie nodded.

Marti had a contemplative look on her face. "They're just sharing."

Lizzie sighed. "You keep saying that Marti."

"Well it's true!" Marti exclaimed. "Smerek says if you like someone you should share with them, that way they like you back."

Edwin and Lizzie shared a wide-eyed look as they finally realized what was going on. Marti, looking satisfied with her explanation, skipped off down the hall. Lizzie's mouth fell open, and closed again. She was lost for words. She couldn't believe her sister could ever...

"You don't think..." Lizzie trailed off.

"No..." Edwin shook his head, "They couldn't be..."

Edwin and Lizzie turned back toward the bathroom just as Casey was coming out. She passed Derek as he headed in. They shared a brief, small smile before going their separate ways. Edwin and Lizzie looked back at each other.

"...Could they?"

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Later that morning, Derek was sitting at the island in the kitchen, while Casey roamed around the kitchen. Lizzie was about to walk into the kitchen when she saw Casey hand Derek a bowl of cereal, before taking her own and sitting down. Lizzie saw the w ay Derek's hand lingered on Casey's when he tookt he bowl. Lizzie saw the smile that passed between them. Lizzie heard Derek say something she had never head him say before.

"Thank you, Case."

But more importantly, Lizzie saw a playful happiness in Casey's eyes that had been absent for a long time.

Edwin came up behind Lizzie, just as she shook herself from her thoughts about the matter before her. "Hey Liz. What's going on?"

"Oh, nothing." Lizzie replied, before continuing on into the kitchen. As she passed Casey she murmured. "Morning, Casey."

"Hey, Lizzie." Casey responded happily, ruffling Lizzie's hair.

"Wha'ts got you so happy this morning?" Nora asked as she walked into the kitchen.

"It's been a good week." Casey shrugged.

Lizzie looked to Edwin then Derek and Casey. Edwin did the same. They didn't know how they could have missed something so big. They didn't know how something so big could happen in the lives of their older siblings and that no one even noticed. Their parents were still oblivious.

"It has been a good week, don't you think?" Derek smiled, his gaze flicking toward Casey momentarily.

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"This can't be right." Edwin replied. He and Lizzie were held up in his room as they discussed the whole Derek-Casey situation. He was trying to rationalize what was going on. "We're trusting the opinion of Marti."

"I know what I saw." Lizzie shook her head, as she paced back and forth. "My sister is happy...and it's because of Derek."

"Maybe we're overreacting. Maybe they're just friends. Maybe they just accepted the situation our families are in--like you and me." Edwin said, blurting out every answer he could think of.

"No. Remember how she was with Sam? It's like that, only more subtle. They're trying to keep it low-key, so Mom and George won't find out." Lizzie explained. "That has to be it."

"My dad is oblivious to everything, but Nora must be suspicious. I mean we all were at first--back when the fighting first stopped--but it blew over."

"My mom is too busy, they're both too busy, to notice." Lizzie shook her head. "I think Derek and Casey know that."

"So what do we do?" Edwin asked.

"I know it might sound stupid, but I haven't seen Casey this happy in a very long time. I don't want to take that from her." Lizzie sighed. "If anyone deserves to be happy it's her."

"Then we don't do anything?" Edwin responded, "We don't say anything?"

"They're happy. Do you want to be the one to ruin that for them?" Lizzie raise an eyebrow. "Cause I don't want to be."

"Maybe you're right." Edwin shrugged.

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Casey had just changed for bed and was tidying up her room when there was a knock on her door. She closed her last open drawer before she turned toward the door.

"Come in." Casey called out as she began to fix up her closet and close the doors.

She turned back around to see Derek's head poke around her door. She smiled as he stepped a little further into her room. Casey took a couple steps closer to him as well.

"I just wanted to say goodnight, Case." Derek said quietly.

When Casey had a clear view of the empty hallway, she gave him a quick kiss. "Goodnight."

"Night, Case." Derek smiled.

Derek slipped out of Casey's room and into is own. Casey was about to close her door when Lizzie appeared in her doorway. Casey frowned, looking confused. Casey stepped back, though, letting Lizzie in.

"Casey can I talk to you?" Lizzie questioned.

"Of course, Lizzie." Casey answered, closing her door behind Lizzie. Lizzie sat down on Casey's bed and Casey followed suit. "What's up?"

""It's really important." Lizzie began. "And it's about you and Derek."

"What about us?"

"Are you two..." Lizzie trailed off, before picking up a different train of thought. "You two haven't been fighting as much lately."

"No we haven't. It was an immature wa y to handle things. I guess we both realized that. We've both matured." Casey explained.

"Derek? Mature?" Lizzie laughed.

"Liz, he's changed so much since we first got here." Casey responded quietly.

"Casey, are you two...you know...together?" Lizzie gulped as she waited for Casey's reaction.

"Lizzie, where did you get that idea?"

"Well, Marti said..." Lizzie started.

Casey's mouth fell open. "Marti? You're trusting something a six year old said? Really? Come on, Lizzie."

"It's not just that, Casey." Lizzie sighed. "I've seen you two together and it's different than just being mature."

"Oh, Lizzie." Casey responded, before taking a deep breath. "Yes, Lizzie. We've been dating for awhile now. Please don't say anything to Mom. She wouldn't understand."

Casey said it all in a rush. Lizzie just watched her face as it fell in defeat. Lizzie wasn't quite sure of what to do.

"I won't say anything." Lizzie promised.

"Thank you, Liz." Casey sighed in relief. "We're going to tell Mom and George, we're just no ready to yet."

"I understand." Lizzie nodded as she started to stand up. "I know I'm the little sister, but you can talk to me if you ever need too."

"I appreciate that Liz." Casey smiled. "Night."

"Goodnight, Casey."

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"Lizzie knows." Casey whispered in Derek's ear as she passed him in the hallway as he headed to his room from the bathroom.

Casey was already walking into the bathroom when what she said finally registered in Derek's head. "What?"

Casey shrugged as Derek followed her into the bathroom. He looked up and down the hall to make sure no one had seen them. He closed the door behind them and locked it. When he turned back to Casey, he looked confused.

"How does Lizzie know?" Derek asked quietly.

"Apparently, Marti said something." Casey answered. She ahad talked to her sister again that morning, before she told Derek. "Something about sharing."

"And Lizzie believed her?"

"I guess so. They've been suspicious of us, before that too."

"So Edwin knows too, I'm sure." Derek sighed.

"Yeah." Casey nodded.

"They aren't going to say anything are they? Because that would be the end of us. My Dad and Nora would never be able to accept this." Derek sounded frantic.

"Lizzie promised that they wouldn't say anything." Casey said. "But maybe we should."

"What?"

"I don't feel right keeping this from them. This is this huge thing in our lives and they are completely in the dark. I don't like it Derek." Casey explained. "They should know. I kind of want them to know."

"You know what that would mean for us don't you." Derek replied quietly stepping closer to her. "Rules and restrictions. No more time alone. Nothing. If they don't end us completely."

"Derek I could do that. I could handle that. I don't want to lie to my Mom anymore."

"I don't like to lie to my Dad either, but if it means being with you..." Derek trailed off.

"What if being truthful means we can still be together? What if they let us stay together?"

"Then I'll do it, if that's what you want." Derek replied after a momentary pause.

Casey looked up at him. "Really?"

"I'd do anything for you." Derek laughed. "It think we've been together long enough for me to be confident enough to say that."

"I won't let this change anything." Casey said, taking Derek's hands.

"I know."

"I won't let them stop us from seeing each other." Casey continued.

"I know."

"I couldn't let you go." Casey kept going on, despite already having Derek convinced.

"Casey! I know." Derek chuckled, smiling, before pulling her closer and kissing her deeply.