Title: The Soundtrack of My Summer

Spoilers from: Season 4... By the way, do any of you know anything about a Life With Derek movie? I've heard some rumors, but nothing solid yet. If you've got the scoop, please let me know and I'll buy you a chocolate cake with your name on it. :)

Summary: It's the summer before Derek and Casey are about to go off to college, so the family decides to spend it in Mexico City. While there, Casey and Derek end up sharing a room, Casey gets a stalker, and Derek figures out just who Casey sees in her dreams.

A/N: I can't believe all of the reviews I'm getting! This is great, guys! Thanks a million!! And by the way, wambling is actually a word. It was on the bottom of my school planner. See, you do actually learn things there! Stay in school, kids!

Disclaimer: If I told you I owned Mexico City, Boys Like Girls and Life With Derek, you'd think I was nuts. Which I am, some of the time. But who isn't?

Chapter 7- Heels Over Head

(Derek's POV)

I, Derek Venturi, have a problem.

No, not one of those ridiculous problems like when I "forget" to do my homework or show up twenty minutes late for school because my hair just didn't look the way I wanted it to. I'm talking an enormous, gigantic, ridiculously huge problem.

I think there is a slight chance that I might be in love with my step-sister.

Yeah, yeah, I can hear you now. 'How can you be in love with your step-sister, Derek? Are you some kind of pervert?'

Well, I'll have you know, I didn't plan on this happening. And I definitely didn't want it to happen either. It just did, and now that I'm so far in over my head here, there's absolutely nothing I can do about it.

Sometimes, you can't help who you fall in love with.

I know what you're thinking. How can he say he's in love? Derek Venturi has never been in love before, not even with Sally! I just figured out my feelings last night, and already I'm using the l-word?

It's sad, but it's true. When Derek Venturi falls for someone, he falls hard. And Casey McDonald is the cement floor that I have just crashed onto at top speed.

Boy am I screwed.

"Derek," Casey whispered, and I shook my head to rid myself of those last thoughts. Anything to prevent another slip-up.

"What?" I whispered back, unsure if she was actually awake or talking in her sleep yet again. This girl really knew how to torture me, that's for sure.

"What time is it, Derek?"

Groaning, I lifted my head off of the pillow that had granted me literally two hours of sleep that night and turned toward the alarm clock on the bedside table.

"9 in the morning. Great, I'm up early again."

"Are you kidding, Derek!? We overslept!! Why, there's so much to do in so little time!"

As Casey continued to ramble about museum exhibits and historical monuments, I slammed my head back onto my pillow, closing my eyes and praying for an extra minute before Space Case noticed I wasn't listening.

"Derek? Are you even listening to a word I'm saying!?"

Way to go, Venturi. That plan worked real well.

"What is it now, Case? I'm tired."

"Casey! Derek! Breakfast time!"

You can bet that woke me up real fast. After a night of tossing and turning, attempting not to think about Casey, and trying my best not to get too excited while lying in bed next to Casey, my stomach was really wambling.

"Be right down, Nora!" I called, leaping out of bed and nearly knocking Casey over on my way out the door. Though I had to admit, the close proximity was a little nice.

As I entered the kitchen and plopped down on my stool, I turned toward my Dad, who was looking at me with a slightly annoyed expression on his face.

It was then that I remembered the way my Dad had walked in on Casey and I last night.

Man that came out wrong. But I have to admit, I like the sound of that.

Basically, my Dad saw Casey and I together in bed last night, and he got a bit nervous. Not that he has anything to worry about, because Casey has way too many morals to ever be involved with me, her step-brother.

Why does that girl always have to follow the rules?

"So what's for breakfast?" I asked hungrily, and my Dad slid a bowl of cereal next to me.

"Mom, I really want to visit some museums today. Can we?"

This was Casey. Obviously, because who else would it be?

"Sure, hun. If you can talk the guys into it."

Looking from Nora to Casey, I scoffed. Did they seriously think I was going to a museum?

"I'm fine with anything you want to do, dear," my Dad whispered, pecking Nora on the cheek.

The one fault with my Dad? He was a huge pushover.

"Well there's no way Edwin and I are going to a museum," I spat, mockery in my voice.

"Come on, Edwin! It'll be fun! Think of all the people who will be there. Maybe you can pick up a few tips on how to make money."

"Nice try, Liz. Edwin's not going to cave, and neither am I."

"You know, Edwin," Casey spoke, a smirk on her face. Did she get that from me? "A lot of hot girls go to museums to look for intellectual guys like you."

"I'm in!" Edwin agreed, and I turned to him in shock.

"Sellout."

"What? They know my weakness."

Punching my little brother in the arm, I turned to Casey with a determined look in my eyes.

"Well, I'm out. And I always get my way. So, we're not going."

"Actually, we are," Casey spoke. "You lost the bet. Therefore, you have to do whatever I say. I say, we're going to the museum. So you have to go along with it."

"Fine!" I spat back. "But this isn't over, McDonald!"

"Of course it isn't, Venturi."

The sexy way she said my name sent shivers up my spine, and I looked away quickly, coughing a few times to regain my composure. Luckily, Casey seemed not to notice.

"When do we have to go?" I asked angrily.

"Actually, now. The first museum opens at ten, and it's an hour away. I want to get there before the lunch crowd piles in."

"Casey, we don't have to rush," Nora reminded her. "We have all day."

"But there are four museums we need to check out, plus a few historical landmarks I've marked along the way. Call the taxi service, George!"

The rest of the morning, as well as most of the day, ceases to recollect in my memory. The museums were boring, as I knew they would be, but I couldn't help but smile at the excited look on Casey's face every time she passed a painting or artifact she really liked.

Of course, if I seemed interested, I had to listen to a twenty minute description of the history behind the piece, which wasn't really worth it. So, I made sure to look away every time Casey turned toward me, just to be sure I could avoid the lectures.

Lunch was fantastic, as usual, but I'll eat anything. The whole time I ate my meal, however, I couldn't help but watch Casey twirl her spaghetti into a tight little knot on her fork. Then she'd lift it to her mouth, some of it would fall off, and she'd slurp it through her lips so fast that no one would notice.

Except me.

I'm pretty sure Casey didn't pick up on the way my face grew hot as I watched her eat, wishing with all my might that I could be that spaghetti.

I would have to make sure Nora and Dad stopped at more Italian restaurants on this trip.

The rest of the day went by with more monuments, art galleries, and complete nonsense. I wondered whether the family even knew what the definition of a vacation was, but then again, who was I to complain? Having Casey along for the ride was good enough for me.

Speaking of the ride, it was now half past five, and we were on our way to a nice little restaurant for dinner.

The first taxi, carrying the 'rents, Liz and Ed, made a sharp left turn. Our taxi, carrying Casey, Marti and I, had no choice but to follow.

Marti was sitting on the outside, because she had been feeling pretty sick and needed to be near the window. That left Casey and me, pressed tightly against each other in a tiny cab as it swerved across the street.

As we made the turn I tried my best not to squish her, but it was pretty difficult. As our arms brushed up against each other, I felt the heat in my body rising out of control.

Casey had an MP3 player on her lap, and as the car swerved, it fell between her legs.

Great. Just one more reason for Casey McDonald to completely turn me on.

The car straightened itself out, and I leaned away as quickly as I could, trying to regain my normal breathing. It wasn't working very well.

"You alright?" Casey asked. "You look like you're burning up. Maybe you caught what Marti has."

"Nah, I'm fine," I struggled through clenched teeth, reaching up to feel my face. It was like a sauna up there. "I'm sure Marti's stomach is just a little upset because of all the ice cream she ate earlier."

"They gave you free refills after two chocolate sundaes!" Marti sighed, obviously regretting her gluttony.

"That doesn't mean you're supposed to eat five of them, Marti," Casey lectured, and Marti nodded.

"Lesson learned, Casey. Could you please open the window a little wider? That turn made me feel a little weird."

"You're not the only one," I mumbled, but luckily Casey didn't hear.

My high-strung hormones were getting a teensy bit out of control, and I had to find a way to calm down or I would most definitely lose it.

Unfortunately, the entire world must be against me today.

The restaurant we ate at was offering a special deal tonight. On none other than spaghetti and meatballs.

Just great.

"But Mom, I already had spaghetti today," Casey persisted as her mother told her what to order.

"I know, honey. But this vacation is expensive enough as it is, and we can use any method of saving money that's offered to us!"

"But I'm sick of spaghetti," Casey sighed.

"Come on Nora. Casey's already had spaghetti today. Why don't you let her get something else?"

As the entire family turned in confusion toward me, I hid my face behind my menu and pretended it was no big deal. Derek Venturi defends Casey McDonald all the time!

"Okay, Case. You can order something else tonight."

Sighing in relief, I managed to control my raging desires for the rest of dinner and most of the night.

I repeat. Most.

The real trouble came when I was climbing into bed next to Casey later that night. After the strange appearance of her old room the other night, plus an anonymous call that Casey received on her cell phone at ten o'clock, she was positive that her room was haunted.

And trust me, I wasn't complaining.

"You know, that call was probably Julio," I suggested as she fluffed her pillow. "You gave him your number, didn't you?"

"Maybe," Casey sighed, sliding beneath the covers. "But why would he tell me to 'beware the full moon tomorrow night?' That doesn't make any sense."

"The guy never makes any sense," I reminded her, settling in with the hope of actually getting some sleep tonight. Not that I was betting on it.

"You're probably right. 'Night, Der."

"Night, Case."

And then, I waited. I practically held my breath as I watched her fall asleep, a peaceful smile on her face. She was having a good dream, and she obviously didn't want it to end.

But what was she dreaming about?

"I love you, you know," she whispered, and for a second I thought that she might have been awake. But the quiet snore that followed those words proved it to be false hope.

"Derek," Casey moaned in her sleep, and my body went rigid. Maybe listening to her dreams was a bad idea. I might start having one of my own, and that would most definitely not be a good thing while Casey was in bed beside me.

Keep it under control, D.

"Derek," Casey whispered in a pleading voice so soft that I had to lean my head over hers in order to hear her. "Will you kiss me?"

And that was when I lost it. Just like when I had confessed my love for her, my mouth seemed to take total control over my mind.

I found myself leaning closer to Casey, my head bent towards her and my hands placed on either side of her body for support.

This shouldn't be happening, I tried to remind myself. Yet I just couldn't seem to stop.

As my lips gently touched hers, I felt a tingling sensation that sent my body into overdrive. Knowing that Casey was still asleep, I managed to control the rest of me while my lips brushed over hers again.

At that moment, we were the only two people in the universe.

Nothing else mattered. Not the family, not our friends, not even our morals. I knew it was wrong to be kissing her, with her completely unaware, yet I didn't care about right or wrong anymore.

Casey McDonald was going to be mine, and there was nothing anybody could do about it.

And that was when, shocked and confused, Casey opened her eyes.