NOTE: The following 'timeline' is based on the tv show's airing, not the timeline established in the show. The first episode aired in 2004 so that's the time frame I used to base all this on. Also, I realize that I mentioned in a previous author's note that this takes place in 2008 and Aelita is 14 but my calculations/research were a bit off. Season 4 aired around 2007, so that is when this story is being taken place making Aelita 13 instead of 14. Sorry for the confusion. The science is probably not accurate so go easy on me. I hope it's easy to follow.

-A.A

Katherine traveled up the stairs toward the history room where Odd was. She crossed her arms across her chest, looking around to make sure that she wasn't being followed by any teachers or, more importantly, by Evan. He was too constricting, too overbearing. She made her way past one classroom and past another. Another and another until she was at the end of the hallway. She stood there and looked at the other end of the hallway, drumming her fingertips against her arm as she contemplated her next move. She had two options in her mind, two ideas. After much more consideration. she came down to one. She looked to her right and leaned forward a bit. She reached out and took hold of the handle to the fire alarm. Gripping it tightly, she pulled it and made a beeline for a tight corner, where she could hide for a few moments. She pressed her body against the wall as the loud screeching of the alarm thundered down the hall, and made its way throughout the building. She couldn't move though, she couldn't hold her ears no matter how much they hurt from the loud noises. Katharine watched as the teachers in each room gave clear and concise instructions to their students. Single file line. No talking. Stay with the class. It's the same thing wherever you go, no matter the country, Katharine thought.

"Come on, hurry up," Katherine muttered to herself. She was relieved to see the teachers begin to take their students out of the classroom after she managed to pull the fire alarm a few minutes ago. She watched as they traveled one class by one, each student in a line more or less, and made their way down the stairs, guided by their teacher. She kept to her corner, turning her head so that they wouldn't see her. Was this a little excessive just to get Odd out of class? Maybe, Katharine thought. But, with this new found knowledge she had - courtesy of both Jeremy and Evan - it was either go big or go home. She had more confidence and courage in her to do bigger things, like pull the fire alarm to get her boyfriend out of class. She could have easily gone and created a diversion to get him out, or make an excuse and casually picked him up but she decided against it. He had just gotten into class -which she knew he was late - and it would be suspicious to try and get him out of class, regardless of the excuse. And, they would never suspect Katharine, the straight A transfer student.

And then, pulling her from her thoughts, she caught the glimpse of the blonde hair with a curious purple streak that belonged to Odd. She smiled widely, slightly out of breath from the adrenaline pumping through her veins. She waited some more, as his class made their way down the stairs, just passing by her until he was one of the last. Quickly, she grabbed his wrist and pulling him away from the crowd and near the dark corner of the hallway. She covered his mouth with her palm and and put her finger against her lips, signalling him to be quiet. His eyes seem to soften at the sight of her and a blush ran to her cheeks. The two waited for a moment, and then she pulled him down the stairs to see that the classes had evacuated the building.

"Kat! What are you doing here?" Odd called out to her in a hushed voice. She smiled widely.

"Getting you out," she said, "Aren't I a good partner in crime?" She guided him through the vacant hallways to one of the emergency exits that was practically hidden in the building. They passed through and saw that there were no teachers, no students in sight and made their way to the woods, toward the factory. He stopped her and she looked at him.

"Hey," he said, catching his breath, "What's going on? Shouldn't you be with Evan?" He didn't notice the slight defensiveness in his voice, but it was there and Katharine noticed but she chose to ignore it.

"Something came up," she explained, "Jeremy called and said he figured it out, Odd. He figured out Aelita's theory."

"Really?" The couple looked at each other and Odd could see her eyes were bright and almost a lighter shade of brown as she nodded. But he didn't know if it was excitement or fear that he saw in her eyes. He didn't know if he wanted to ask either. But what he was curious about was Evan. What happened after he left? Not much, he figured, because of the short amount of time it took from arriving to class to the escape. But he still wanted to know.

"So-"

"C'mon, I'm sure everyone is there already," Katharine interrupted and took hold of his hand, intertwining their fingers. He softened once again and forgot about his earlier curiosity. She pulled him along, walking toward their secret path through the underground tunnels.

"Wait," he said with a chuckle, "Did you have to pull the fire alarm, though? I almost had a heart attack when it went off." She giggled and looked back at him as they entered the tunnels and each grabbed a skateboard.

"But it was fun, wasn't it? The thrill of it, don't you feel alive?"

The two made their way to the factory and traveled down the elevator to the Supercomputer where the others were waiting. The elevator opened and the couple, with their hands intertwined with one another, saw the other Lyoko Warriors turn to them as they stepped out. Aelita smiled widely and pushed through the group to get to Katherine and put her arms around her, hugging her deeply. Odd stepped away and allowed the two newly found sisters to have a moment. Katherine was shocked at first but soon wrapped her arms around her waist, softly and almost hovering over her waist, careful not to touch.

"I told you," Aelita said softly as the two hugged, "I told you it was true." Katharine didn't say anything and stepped away from Aelita with a soft smile. Aelita looked at her with soft and glistening eyes, a smile across her face. Katherine looked and wondered where the resemblance was, where she could possibly look like Aelita but she saw nothing. Maybe, she thought, it's denial of it all. There was an awkward cough and the sisters looked to see Jeremy smiling awkwardly.

"Uh, c'mon guys. I wanna explain it to everyone," he said shyly. Aelita didn't need an explanation. As long as there was proof that she wasn't crazy and that Katherine was indeed her sister, she would fine and at peace. But Katherine wanted to know, so she walked toward Jeremy and crossed both arms across her chest.

"So," said Ulrich coldly, gesturing to Jeremy and in a similar position to Katherine, "go ahead, genius." Jeremy pushed his glasses up the bridge of his nose and nodded, going to a desk on the other side of the room. He came back with a small black notebook and took a deep breath."Alright, bare with me, guys," he said as he began to flip through the pages of the book. Aelita looked to see that it was her father's secret journal, the one she had found hidden away in the Hermitage. Jeremy looked up and set his eyes on Aelita.

"Aelita, how old are you?"

"13," she answered. Jeremy turned to Katherine, "And how old are you, Katharine?"

"Last time I checked, 15," she replied. Jeremy nodded and began to flip through the pages, "So if Katherine is supposedly the younger sister, how is she the younger sister if she is clearly older than Aelita?"

"You tell us, Einstein," teased Odd.

"Well," Jeremy said, "That's what stumped me. I had no idea how to figure out or how to prove what Aelita was telling me that Katharine was her younger sister. But I figured something out. According to Dr. Hopper, your sister was stuck in Lyoko around 1990 and she was born in 1987, making her three years old at the time. And Katherine was born in 1993, according to her records, so how can the two be the same person? I thought it was impossible. It wasn't long after her disappearance that Dr. Hopper stopped writing in his journal so there wasn't much to go on. I kept thinking that maybe he failed, maybe the child was still on Lyoko. But that was even more impossible," Jeremy said. The group watched on as he explained his findings, almost as if he was talking to himself.

"So, instead of focusing on how to prove that Katherine specifically was this baby, I focused on the possibility of getting that baby back to Earth and the effects it would have. And it was because of this that I came to the conclusion that I'm going to tell you guys now. Hypothetically, if the baby did survive and Dr. Hopper did manage to get her back to Earth, what would happen? Well, the same thing that happened to you, Aelita."

Aelita looked to see that the other members of the Lyoko warriors with their gazes now transfixed on her. She seemed frozen and her eyes widened, but her brows furrowed with confusion.

"What do you mean, Jeremy?"

"I mean, Aelita, what happened to you after you were materialized on Earth?"

"Well," she said, "I assumed life here, posing as Odd's cousin." Jeremy smiled and nodded, a slight blush on his cheeks that was always there whenever he talked to Aelita.

"Exactly! You had to assume to a new life here because you had no files and I wanted to keep you close-"

"You did?" Ulrich teased. Jeremy pushed his glasses up and coughed, tugging on his neck of his turtleneck sweater.

"I meant we wanted to, of course. But that's besides the point, the point is that Aelita had have an entirely different identity not only because her records had her born in the 1980s but because she had lost her memory. She had no recollection of who she was," Jeremy explained, "So, with that being the case, I thought to myself that that is probably what would have happened is said child was rematerialized on Earth. It would have no idea who Dr. Hopper or Aelita was."

"So? What does that have to do with anything?" asked Yumi. Jeremy smiled and continued, flipping to the journal and laying his hand down to save the page.

"It's important because that's where I started, that's where Dr. Hopper would have started. If you finally had your daughter, but she had no memory of anything, what would you do? She didn't know you were her father and she screamed every time she saw you because she thought that you were a stranger and someone who would harm her, what would you do?"

"My father," she paused and looked at Katherine with a somber smile, "Our father, actually, was never the same after that. I don't remember you, when you were a child but around the time you disappeared, every December that I could remember, he would be locked away in his office. Scribbling code and screaming at his computer program like a madman. I think I know what you're saying Jeremy. If you couldn't remember him, he would have been heartbroken, Katherine. He wouldn't have been able to cope it. He might've been angry, he might've been sad or depressed most of all but he always was after my mother disappeared. So, I think he sent her away." Jeremy nodded.

"Yes, exactly Aelita. He sent her away but that's where another problem was, well - two problems really."

"What were they?" asked Ulrich.

"First," Jeremy said, "Dr. Hopper wasn't the type of person to leave breadcrumbs, so to speak. He wouldn't have take the child to a local adoption center or hospital where he would have to sign papers in his name. He would've have it so that if anything happened, if the people who took Aelita's mom came back, perhaps, they wouldn't be able to trace her back to him. So, in a sense, he was protecting both Katherine and Aelita and himself." Aelita smiled, thinking of how resourceful and quick witted her father was to have thought of such an elaborate plan.

"And the second problem?" asked Katherine, who remained mainly silent for the most part of the explanation so far. She wanted to listen extremely carefully in order to get every word of information, to process it and try to understand it as Jeremy understood it.

"The second problem, Katherine, was that I didn't know when to look. When as in the year. There was never any definite date that I can go on that said he managed to rematerialize you - uh, the other Katharine, sorry. So I was missing two of the most major pieces of evidence I needed to prove Aelita's theory. The where and the when," Jeremy explained.

"So, how'd you figure it out, genius?" Odd asked.

"It's a lot of trial and error," Jeremy said, "First, I had to figure out the when, the time the daughter was rematerialized and sent away."

"But how do you know she was rematerialized at all?" asked Yumi, "Maybe Dr. Hopper never found her and couldn't figure it out.""You're right, Yumi. I thought about that too. It was when I came to that problem that I had to switch tactics. Instead of being hypothetical, I had to think of Katharine and her past to possibly connect her somehow. So, I had to think of a way to possibly link Aelita and Katherine. But, how would you do it?"

"I'm sure you found a way, Einstein," commented Odd with a smirk. Jeremy chuckled and headed to the Supercomputer. He sat in his chair and began to type quickly on the keyboard.

"You're right, Ulrich. Usually, when you want to see if two people are related, you go to a laboratory and get tests done. But, we don't have that kind of time and honestly, I don't have that kind of patience. So, I found a solution and I can't believe I didn't think about this before! It was staring at me right in the face!"

"What was?" asked Katherine.

"The Supercomputer!" he exclaimed as he typed, "All the answers were here all along and I just didn't use it properly. The Supercomputer keeps record and storage of all of those that enter Lyoko, every single time and every single strand of DNA. And, both Katharine and Aelita have been to Lyoko and share the same power to deactivate the towers. But I didn't compare Aelita's and Katherine's genetic makeup - oh no, that's not nearly as accurate. What I did was I compared and analyzed both genes against Dr. Hopper's. I didn't even realize his genetic makeup was still in the Supercomputer, but it was! We know for a fact that Dr. Hopper is Aelita's father so I focused on Katharine's genetic makeup and compared it to Dr. Hopper's and as Aelita said, I was able to come to the conclusion that he and Katherine are related. And therefore, that Aelita and Katharine are also related, more specifically, they are sisters."

Jeremy seemed exhausted after talking so quickly and for so long, he was out of breath. Aelita let out a squeal of excitement and wrapped her arms around Katharine once again and hugged her tightly. Katharine returned the hug gently, with less enthusiasm and more confusion. Aelita felt as if she was on Cloud Nine, she was ecstatic to know that she wasn't crazy. She knew that she was right. She was finally reunited with her baby sister, with Katherine. But then her brows furrowed and she released Katharine, turning back to Jeremy.

"Wait a minute, Jeremy," she said, "There's still one thing I don't understand. How is Katherine older than me? How did Ulrich's family find her, it seems a bit too coincidental that they found her." Jeremy blushed and rubbed the back of his neck and tugged on his sweater that stuck to his sweaty neck.

"Well, you see, I don't know. There wasn't any more evidence or theories that made any sense to me. Without a when or a where, I can't figure out when Katharine was rematerialized and found her way to Ulrich's aunt's family. So, I came up short. I'm sorry, Aelita." There was an eerie silence that ran through the Lyoko Warriors, an almost depressing and desolate silence because the Einstein hadn't really figured out the rest of the puzzle. He felt disappointed in himself as well. He thought he would solve it, he tried for hours trying to piece together a reasonable theory and back up with evidence but it all fell apart in the end. He even missed a few of his less important classes (with a reasonable excuse) in order to try and brainstorm some more but still, there was nothing.

"I know what happened." Heads shot up at the voice and eyes followed to face the voice. It was Katherine with a shy and nervous smile on her face, "I can fill in a few blanks."