After the tower was deactivated the group was devirtualized leaving Katrina on Lyoko all by herself. Ulrich was happy to finally be reunited with his sister after being apart for five years but was saddened to leave her alone on a virtual world.

"Do you think Code Earth will work on Nina?" Ulrich asked. Jeremy shook his head.

"Code Earth was designed specifically for Aelita. I would have to reprogram it using Katrina's DNA, but even then, it most likely wouldn't work. There are too many bugs in the program. She could wind up lost forever" Jeremie explained. Ulrich didn't like the sound of that. It was bad enough that she disappeared in the first place. Now there was a possible chance she might disappear forever. Ulrich balled his hands into a fist in frustration.

"It's okay Ulrich. We'll find a way to get Katrina back" Yumi reassured him placing her hand on his shoulder. Later that day, they all went to class. Jeremie, Ulrich, and Odd were in Miss Hertz's class. Ulrich was too distracted by the situation with his sister to pay attention to the lesson.

"Ulrich!" Miss. Hertz called on him.

"Huh?" He responded coming out of his daze.

"What's the answer to the question on the board?" She asked. Ulrich examined the question on the board. After some thought he couldn't come up with an answer.

"Uh...I don't know" He said giving up.

"Well maybe if you paid attention you would know" She stated sternly with a slight glare. She went back to teaching as she explained the answer to the question on the board.

"Hey, no need to be so glum. Jeremie said he was going to re-work the program later after school" Odd whispered to him.

"Uh huh" He responded not really paying attention. The bell rang dismissing the class. Ulrich went straight to his dorm not in the mood to be around other people. They just let him be for now. Odd and Jeremie went to the cafeteria to meet up with Yumi and Aelita, who were already sitting at the table eating their lunch. They got their food and sat down at their table.

"Where's Ulrich?" Yumi asked.

"He decided to go sulk alone" Odd replied.

"I guess he's really close to his sister since he's so upset" Aelita commented.

"Yeah he seemed so happy to finally see her again after being apart for five years" Yumi chimed.

"If I manage to get a hold of a sample of Katrina's DNA, I should be able to re-program Code Earth to work devirtualize her." Jeremie mentioned.

"How are we going to do that? It's not like Ulrich could just go home and find something in her room that would have any of Katrina's DNA on it" Odd commented.

"Wait, isn't Katrina's DNA already in the computer? Why can't we use that?" Aelita questioned remembering seeing Katrina's DNA sequence on the screen the other day.

"I might be able to use it if it's not corrupted by a virus, I'd like to get a backup sample just in case. If I use the same program I used to materialize Aelita's DNA, I should have no problem materializing a sample of Katrina's" He explained.

"So, are we going to head to the factory?" Yumi questioned.

"No not yet. I'll let you guys know once I'm done" Jeremie said. He finished his lunch and got up from the table. He threw out his garbage and headed to his dorm. Aelita met up with him after she finished.

The two were in Jeremie's dorm trying to figure out a way to materialize Katrina. Jeremie sat at his computer while Aelita sat on Jeremie's bed with the laptop. Jeremie tried to contact Katrina using the same method he used when Aelita was in her situation. Soon enough Katrina's face popped up on his screen.

"Hi, you must be Jeremie. It's nice to put face to voice" Katrina greeted with a soft smile.

"You know, you look nothing like Ulrich" Jeremie commented.

"Thanks for the compliment." She responded. Aelita placed the laptop down on the bed and got up from the bed walking over to the computer.

"How close were you and Ulrich before you got stuck on Lyoko?" Aelita asked.

"Well we had a typical sibling relationship. We fought a lot of little things, but for the most part we got along fine" She answered.

"Do you remember how you got stuck on Lyoko?" Jeremie asked. Katrina shook her head.

"No before I got here, I was an intern at a computer lab that was funded by the government" She told him.

"Do you remember who was in charge of the lab?" He asked. Katrina shrugged her shoulders.

"I'm not too sure, but I think his name was Dr. Franz Hopper or something" She replied. Both Jeremie and Aelita seemed surprised by this. Katrina used to work with Aelita's father.

"Well we just got our answer. Franz Hopper is the one who created Lyoko" Jeremie told her.

"He's also my father" Aelita mentioned.

"Oh, you're the daughter Dr. Hopper used to talk about. He mentioned that his goal was to create a world where he could keep his family safe" Katrina stated.

"Anyways, we're going to try and find a way to rematerialize you back on Earth. We need a favor from you though" Jeremie told her.

"What is it?" She asked.

"I need you to go to Sector Five and retrieve some data for me" Jeremie stated.

"Sector Five? I've never heard of that sector before. I only know of Forest, Desert, Ice, and Mountain sectors" She commented.

"Maybe I should go to Lyoko and take her there" Aelita suggested looking at Jeremie.

"It would be too risky for you to go by yourself" He noted.

"Excuse me, but I think I'm more than capable of acting as someone's escort" Katrina commented feeling offended.

"Well if you lose all your life points, you'll disappear forever" Jeremie mentioned.

"Yes, I'm well aware of that" Katrina commented.

"We could at least bring Ulrich. He's been acting all depressed since our last trip to Lyoko" Aelita then suggested.

"Ulrich is always like that though. I haven't seen my brother in a good mood since he started middle school" Katrina mentioned. "My father is partially to blame though if I were to be honest. He's always so hard on Ulrich especially when it comes to academics. If Ulrich got so much as a C on his report card, he was grounded, and I usually would be the one stuck tutoring him and if I refused, I would also get punished" She continued.

"That explains why he's so reluctant to go home" Aelita chimed.

"Anyways, I guess we could wait for Ulrich. I mean since I don't exactly know what to do in this Sector Five area it would make sense to have someone else there as back up" Katrina stated.

"Alright then, well do this tomorrow. I'll let Ulrich know what's going on" Jeremie stated.

"Okay, I'm gonna go, I think I hear some movement outside. I'm gonna go check it out" Katrina said before ending the video transmission.

"Do you think Ulrich is going to be up for it?" Aelita questioned.

"It involves his sister, so I don't see why not" He responded. Jeremie went back to re-coding the program after Aelita said her goodbyes and left for the night.