Aelita has a nightmare, one which has been recurring ever since she was materialized on Earth a few days ago.
Jeremie does some investigating on the Internet about The Hermitage, and after a night of hacking, finds the deed to the house, signed by Franz Hopper. He also finds that there used to be a science teacher at Kadic with the same name, and wonders if they're the same person. Ulrich thinks it's likely, but Jeremie wants to be sure, and suggests checking Kadic's archives. Jeremie further suggests a connection between the Hermitage and the equipment in the Factory, and Lyoko too.
Aelita goes to the bathroom for a shower, only to find a long queue outside. It turns out that Sissi is occupying the bathroom and making everyone wait, which apparently happens a lot at Kadic. Sissi notices Aelita and tells her that with such a long queue, she might be waiting for a few hours, but adds that upstairs there are showers with no girls at all.
Aelita goes upstairs to the shower room, but it turns out that Sissi has played a cruel trick on her; it is the boys' shower room. Ulrich and Odd gently escort her out, and find Sissi, Herb, and Nicholas there, watching. Ulrich gets angry at Sissi for playing such a trick on Aelita, when she knows fully well that Aelita will easily fall for such things. Sissi doesn't appear to care. To make things worse, Jim tells Aelita off for trying to enter the boys' shower room.
Aelita meets Yumi and tells her about the recurring nightmares. Yumi assures her that it's just because she's not used to living on Earth; she's only been here for less than a week.
Jeremie sneaks into a room to check Kadic's archives, while Ulrich and Odd keep watch. He finds a document signed by the teacher Franz Hopper and compares the signature with the one on the deed to the Hermitage; they match, proving that they are the same person.
Jeremie, Odd, and Ulrich visit the Hermitage. Jeremie discovers a few history books on a shelf, including one about Carthage, which he knows a little about because they learned about it in school the previous year. Jeremie takes the book about Carthage.
At Kadic, Aelita is on her own in the cafeteria, trying to get lunch, but is unfamiliar with the workings of a cafeteria. Behind her, people waiting in line are getting impatient, and complain at her. She gets uncomfortable and gives up. For a moment she is relieved as she sees Yumi, but when she notices that Yumi is interested in William at her table, she gives up trying to get lunch and goes outside.
She meets Sissi outside the entrance, who starts being unkind to Aelita again, suggesting that she return up north. Aelita, distressed, tells Sissi that at least she'd feel at home there, and runs away into the trees.
In class, Mrs. Hertz notices that Aelita is not present, alerting Jeremie, Ulrich, and Odd to this too. Sissi tells them that Aelita has gone back to Canada, and recounts their last exchange. Jeremie pretends to be ill and asks to go to the Infirmary; Ulrich and Odd accompany him.
Jeremie quickly figures out exactly where Aelita must have gone; she has returned to Lyoko. They all race to the Factory with Yumi.
On Lyoko, Aelita has virtualized herself into the Forest, but finds herself under attack by Blocks.
Jeremie sends Ulrich, Odd, and Yumi to Lyoko, where they find themselves under separate attack. They battle, trying to get to Aelita, but encounter heavy resistance. Jeremie sends them their Vehicles.
Unexpectedly, a white orb with the Eye of XANA on it appears out of nowhere and engulfs Aelita. Jeremie loses touch with her; she has completely disappeared from his detectors. Yumi panics, fearing that Aelita has been killed by her attackers, but Jeremie thinks it isn't that. He finds that she has disappeared from the sector, and has actually disappeared completely from Lyoko.
Aelita leaves the orb, and finds herself in a blue, spherical room. An opening appears in the wall and she walks through it to explore, but is harassed by slug-like monsters called Creepers. She encounters a huge monster with many tentacles - the Scyphozoa.
The remaining three on Lyoko continue to be attacked as Jeremie figures out what has happened. Jeremie discovers a fifth sector of Lyoko, one that they didn't know about before. It is named Carthage. Figuring that Aelita must be there, he tries to figure out how to get there, and finds he needs a code.
Ulrich tells Jeremie to hurry up, as the attack on Lyoko is getting fierce. Jeremie guesses that the code is related to the historical Carthage, and looks in the book he took from the Hermitage for words that might be the code. After trying many and failing, he thinks about it logically. He wants to get into Carthage, and to do that, he has to conquer it. He finds the name of the person who conquered Carthage, and enters it as the code: SCIPIO.
The white orb appears again on Lyoko, making the attackers back away. It engulfs Ulrich, Odd, and Yumi, and carries them through the forest at high speed, to a white void where many of the wires that run through the forest converge.
The orb travels through a dizzying arrangement of moving walls and arrives in what appears to be the same room Aelita arrived in. The three leave the orb and go to search for Aelita. They find her being attacked by the Scyphozoa, which Jeremie finds is stealing her memories. They attack it until it releases her.
The walls begin to close around them, and Jeremie tells them to hurry back. They return to where the orb dropped them off, and Jeremie calls another orb to return them to the Forest. Aelita enters a tower to devirtualize, while Jeremie materializes the other three directly from Lyoko.
Back on Earth, Aelita apologizes for running away. The others comfort her, letting her know that they understand how difficult it is for her. Sissi comes to gloat, and Aelita surprises everyone by countering with an insult of her own.
This episode contains examples of:
- Alpha Bitch: Sissi gets more ruthless in this season, attempting to expel Aelita just because she's new and not used to the same social conventions. Not helping matters is that Aelita is already friends with Jeremie, Yumi, Odd, and Ulrich, who she already holds respective grudges over (and one unrequited crush on Ulrich).
- Ask a Stupid Question...: While not entirely stupid, Ulrich asks Jeremie where he's going when they and Odd get out of the classroom. Fortunately for Ulrich, Jeremie answers without sarcasm that he's going to the factory to find Aelita.Odd: (seeing one of his buddies running down the hall, having exited the same room) Jeremie, wait! Hey!Ulrich: Where are you going?Jeremie: To the factory!Odd: (worried) You think Aelita's there?Jeremie: She told Sissi she was going back to Canada. I think she meant, "I'm going back to the place where I came from," which means Lyoko!
- Berserk Button: For the first time ever, Sissi shows annoyance at being called her real name, "Élisabeth".
- Continuity Nod: Odd casually mentions his lingering disbelief in how Ulrich actually kissed Sissi once before. Ulrich makes it clear how he doesn't want to be reminded of it and calls it "ancient history".
- The Cracker: Jeremie has to work out the password to access Sector 5, which he correctly deduces is related to the book he found in the Hermitage.
- The Dog Bites Back: After taking crap from Sissi all day, Aelita manages to burn her with a zinger that leaves the rest of the Lyoko Warriors in an uproar.Sissi: A beautiful flower like myself needs to be watered.Aelita: Yes, you never know. You might even sprout a brain.
- Is This What Anger Feels Like?: Sissi makes Aelita flee the school by exploiting her naïveté, getting her into trouble... all because she's a newcomer that's friends with Jeremie and the others. Her driving force is anger, powered by sadness and regret leaving Lyoko, and as Jeremie says to her later, she was right to be confused about all the new emotions she hasn't experienced yet.
- Innocently Insensitive: Yumi accidentally ignores Aelita in the lunchroom, sitting near William, causing her to go away hungry and alone.
- Laser-Guided Amnesia: The Sychphozia is programmed to extract Aelita's memories, and Jeremie later theorizes that XANA is looking for something really specific only Aelita knows, but is also otherwise wiping her mind, hence the need to save her.
- Malevolent Architecture: Carthage, the 5th sector, is introduced in this episode. Near the end of the 3-minute timer, the whole room begins to reconfigure, and the Lyoko Warriors only just make it out without being crushed. It's worth mentioning at this point that Carthage embodies just about every variation of this trope, including crushing traps, bottomless pits and moving platforms. And all this on a timer.
- Mobile Maze: As part of Sector 5's Malevolent Architecture, after the timer finishes, the whole sector has a new layout, meaning a second run will be different.
- New Powers as the Plot Demands:
- Season 1 showed that none of the Lyoko warriors can dematerialize from Lyoko without being killed, with this specifically being an issue in "Image Problem", as Yumi needs to devirtualise, but can't, so she asks Ulrich to kill her. Starting from this episode, it seems that Jeremie has finally worked out how to dematerialize everyone except Aelita on command (who requires going to a tower to dematerialize).
- Aelita can also work the scanners by herself. Considering it's implied she had knowledge when she was a Lyoko denizen anyway, this makes sense.
- Oh, Crap!: Jeremie and the others realize this when Aelita doesn't come to class. The Armor-Piercing Response Sissi gives drives the point into them.Sissi: (to Mrs. Hertz) Well, I do, Ma'am! She went back to Canada!Jeremie: Canada?!Sissi: Yeah! That's what she told me. She even said, "At least I feel at home there."
- Savage Wolves: Aelita has nightmares about them, though at this point, she can't figure out why.
- Sensory Overload: Part of what makes her run away from school and back to Lyoko is her inexperience with eating, Sissi's bullying, Yumi ignoring her (by complete accident), which makes Aelita feel deep regret for leaving, and runs off to Lyoko.
- Unnaturally Looping Location: Sector 5 is made to have rooms that look as identical to each room as possible.
- The Walls Are Closing In: One of the features of Sector 5's hallways.
- Wham Episode: This episode marks the debut of the new sector, Sector 5, and new monsters such as the Creepers and, most notably, the Scyphozoa.
