A/N: Based on the story created by foeri. Read & Review!

After the battle with Mandark, things went back to normal. Blossom and Dexter spent more time together with experimenting. Since Bubbles joined the Eds, Eddy's businesses are unusually successful. Buttercup has almost finished her training at the Xiaolin Temple. However, their relationship is not on top. One day was a normal day of class in school. Blossom was attentive like Dexter, ready to take notes, Bubbles balanced her school supplies, Buttercup looked bored, Mandy had a deep scowl at her desk, Mac was ready for the lessons, Double D was excited to learn, Ed was writing notes on his dangling tongue, and Eddy was leaning back lazily.

'Powerpuff Girls!' the sharp voice of the principal called over the intercom. 'Into my office NOW!'

Blossom looked curious, Buttercup looked annoyed, and a book landed on Bubbles's head.

"Oh, boy..." Buttercup narrowed her eyes.

The Girls went to the principal's office, passing the animal secretary on their way into his office door. "Good morning, Mrs. Warthog!"

The warthog woman merely glanced at them on their way.

"Thank you for coming, Girls," Principal Pixiefrog looked to the sisters as they sat in chairs in front of his desk. "There is a very serious problem I'd like to talk to you about. Have you got any idea how much it costs to fix the roof every time when you use that as a door? And of course, the insurer doesn't pay. So now, I've decided to forbid you from flying in school. You must use the door like everybody else. Nevertheless, I'd like to-" he was cut off as he answered the ringing phone. "Yes, Mayor? They are right here. All right, I'll send them," he then hung up and looked back to the students who were superheroes. "The Mayor asked you to visit a scene at US Robotics Headquarters, but please, don't break the roof."

The Girls flew through the window instead as they were ready to spring into action.

"Note to myself: Next time, I tell them to prohibition that concerns to windows too," Pixiefrog muttered to himself, then pushed on his call button. "Mrs. Warthog, call the insurer! The eagle has landed."

"Again?" Mrs. Warthog groaned through the call system.

A few miles away, the Girls made it to their destination and landed, ready to fight any crime if necessary.

"Good morning, Powerpuff Girls," a robot greeted them. "My name is Larry 3000, I am the personal computer here. I called you. Thank you for coming so fast, come this way." he went to lead them.

"What happened, Larry?" Blossom asked.

"Our dearest scientist, the head and founder of the company, the creator of the three laws and my master, Professor Moshimo has committed suicide this dawn."

Blossom saw the fallen scientist and cringed. "Ugh, not a pleasant sight!"

The Professor was shown behind some police tape and was on top of a puddle of his own blood as twin red-headed girls who looked young, but older than the Girls, and had lab coats.

"This is Susan and Mary Test," Larry introduced. "They will answer questions in what follows."

"I still don't believe it!" Susan hissed, looking more angry than her twin sister.

"How did it happen?" Blossom asked.

"He jumped out of his office on the 36th floor."

"We'd like to see his office if it's possible."

"Sure, no problem, follow us."

The Test twins led the Girls with them to the professor's office as requested.

"This place is freaking me out." Bubbles whimpered.

"What are you looking for?" Mary asked.

"I don't know, maybe nothing, it's just a procedure." Blossom answered honestly and curiously.

"I say something stinks here." Buttercup folded her arms.

"How well did you know the professor?" Blossom asked the super genius twins.

"Quite well," Mary answered. "We used to work together."

"We were his assistants for two years now." Susan added.

"Was he suspected to suicide?" Blossom asked.

"I'd never thought of that," Mary had a tear roll down her cheek. "He was working on a big shot that could change the world forever."

"He invented some kind of new domestic robot to make our lives easier," Susan frowned. "He was a genius."

"Girls!" Blossom called to her sisters. "Did you find anything?"

"Nothing." Bubbles replied.

"It wasn't suicide." Buttercup added.

"Buttercup, don't read something into the case," Blossom folded her arms to her. "By the way, what's your evidence for what you state?"

Buttercup picked up a chair, then hit it against the window, but the chair bounced against it to show it was still glass and not an open window. "It's shatter-proof glass. I don't think an old man like him could break it so easily."

"You're right!" Blossom understood that now. "Who was here for the last time?"

"No one was here for a week now, except him." Susan informed.

"We'd like to see the security cameras."

"Of course."

"Or maybe, the murderer is still here." Buttercup looked grave.

"Oh, please!" Blossom rolled her eyes. "Don't tell me that you're thinking what I think you're thinking what you think."

Buttercup glanced at her in return.

"Oh, boy..." Blossom mumbled. "Look, it's impossible. A robot could not kill a person. It's against the three laws. That's why they were created."

"I know that, but there's a law someone will break that once." Buttercup gathered.

"What laws?" Bubbles asked clueless.

"Law 1: A robot may not injure a human being or through inaction allow a human being to come to harm." Mary recited.

"Law 2: A robot must obey any orders given to it by human beings, except where such orders would conflict with the first law." Susan added.

"Law 3: A robot must protect it's own existence as long as such protection does not conflict with the first or second law." Mary then finished.

"Oh, I've got it," Bubbles now understood. "Then, Blossom's right."

"Don't be so naive, Bubbles," Buttercup crossed her arms. "However, I still think you're wrong."

There was a pile of garbage with screws and sprockets. There was a blue toy-sized robot with red eyes. It came to life suddenly and flew off with its rocket powered feet.

"GET IT!" Buttercup yelled as the robot went off.

Buttercup flew after the robot as it flew all around town. It tried to blast her with its laser eyes, but Buttercup dodged and laser blasted back. Buttercup and the robot fought, but it caused buildings to catch on fire. Buttercup kept dodging, saw an empty baby carriage and got it out of the way to pound this robot, though it caught her after transforming once she got a car to use as a shield.

"BUTTERCUP!" a voice snapped.

Buttercup fell and hit the road hard.

"BUTTERCUP!" the voice continued, now being familiar.

"What?" Buttercup stood up, rubbing her head, to see her sisters folding their arms, glaring down at her.

"What the heck are you doing!?" Blossom snapped at her. "You are running half the city while chasing a toy!"

"NO! I was following the suspect like you should too!"

Blossom looked at Buttercup like she was crazy, did she really think a toy caused all this trouble? "What suspect? What are you talking about? That's just a stupid toy! There's nothing inside, just wires and circuits, the whole thing is controlled by processors and computers, and articial intelligence, it cannot kill!"

"Well, it's a very interactive toy," Buttercup still refused to let Blossom win this argument, she should know, her life was threatened and not her bossy leader sister's. "As I observed, it was armed, and turned into a killer Terminator thing."

"This adorable little robot?" Bubbles scooped up the killer 'toy' in her arms, feeling like a nurturing mother like with anything helpless and defenseless in her eyes. "I don't think it could hurt anyone."

"You'd be surprised." Buttercup scoffed.

"Once again, Buttercup, a robot cannot kill." Blossom turned her back, still folding her arms.

"Then why did it run away?" Buttercup challenged.

The Test twins came to the scene.

"I think we can answer that question." Mary said.

"US Robotics cares for its latest inventions," Susan began to explain. "The built-in stealing-proof systems could be easily noticed escaping in a high-tech robot like that."

"See, that's the answer." Blossom narrowed her eyes to Buttercup, satisfied that she was right.

"And what about the transformation?" Buttercup asked, still angry that she wasn't believed.

"Well, it can't." Mary replied.

"Well, I've seen up close that it can!" Buttercup retorted.

"Impossible," Susan spoke then. "We don't accept military projects like that. Moshimo was a pacifist."

"DON'T TOY WITH ME!" Buttercup waved her arms in frustration. "I know what I saw! I didn't destroy the city, that goddamned robot did! Also, it is the killer!"

"Buttercup, calm down, it wasn't suicide," Blossom tried to coax. "That's a fact, but forget the robot."

"Who are you with, Bubbles?" Buttercup asked, she hoped her other sister was at least on her side, this was really aggravating for her.

"Umm..." Bubbles tried to think, but she wasn't sure just who to side with on this one, but she had a possible idea. "I think we should examine every opinion and maybe ask for some specialists' help too."

"So much for teamwork," Buttercup snorted, then flew away in a huff, abandoning her sisters. "I'm leavin'."

"And what should we do with Robotboy?" Bubbles asked as she was still carrying the little toy-sized robot who actually caused a lot of damage. "Can we keep him?"

"Unfortunately no, we must take it back to the company," Susan declined. "It's a secret."

"Okay, we'll keep in contact," Blossom waved to the Test twins. "Inform us if you find something," she then looked back to her blue sister. "Bubbles, let's go back and investigate!"

Bubbles and Blossom then flew off together.

"Do you think Buttercup might be right?" Mary asked her sister.

"Well... If she is, that would be a very, very, very serious problem." Susan thought out loud as she scratched her chin.