After discovering Aelita's link to the supercomputer and the inability to shut off the supercomputer that stems from it, Jeremie works hard to find new and better ways to fight X.A.N.A.. To that end, he develops new vehicles for the group. He also develops a new tower-scanning program that instantly detects activated towers, allowing Aelita to live on Earth full time. While on Lyoko using their new vehicles for the first time, they encounter a new creation of monsters X.A.N.A has made, the Tarantula as named by Odd.
While adjusting to her new life, the class takes a trip to the nearby woods for a scientific field trip. Ulrich wants to partner up with Yumi while rehearsing lines to himself as a way to tell her how he feels about her, but she's already partnered up with a new kid named William. He comes from another school, having been expelled from it, inciting jealousy in Ulrich. During the field trip, Aelita and Jeremie partner up. Jeremie is forced to retrieve his laptop to be alerted to a possibly X.A.N.A attack, leaving Aelita in the woods.
Meanwhile, Ulrich is observing and watching Yumi and William on their assignment. Despite Odd's encouragement that Yumi is "crazy about him (Ulrich)", Ulrich himself isn't so sure. Odd remarks how he can never figure out Ulrich's relationship with Yumi out and asks if they're going out together or not. Ulrich says "not really" describing it as "complicated". As he zooms his camera in on Yumi with William, he says that he bets that William "is completely snowing her". During this, William talks with Yumi and saysg that he wouldn't consider himself a "rebel" he's just "a little rebellious". He then admits that he got expelled from his previous school for putting up love letters all over the school ground. Yumi asks him if "love makes him crazy", he says that it makes him "totally insane", inciting a blush from Yumi.
With Jeremie gone, Aelita is frightened by visions of wolves and takes off into the woods in a panic. At the academy, Jeremie gets to his laptop just in time to see an alert that X.A.N.A is attacking. In the woods, he calls Ulrich and Odd to let them know and asks if Yumi is with them. Ulrich says that he would prefer it if Jeremie would call Yumi himself. Jeremie calls Yumi as William continues to flirt with her, causing her to take off to join the others when William isn't paying attention.
Aelita is eventually lead to a house known as the Hermitage. There, she has even more visions - of the house in well kept condition and of a man playing the piano inside - and is attacked by X.A.N.A. as she tries to make sense of the visions.
Once the others arrive to find her, they learn that X.A.N.A. has possessed the house and uses a variety of objects in it to attack them. While the three evade X.A.N.A's attacks them, they realize that he is leading them somewhere and find Aelita unconscious in a sauna in the basement. Just as they get to Aelita, who becomes conscious, she warns them that it's a trap. At that moment, the metal door begins to close in order to trap them all inside and boil them. However, Odd manages to keep the door open long enough for Aelita to escape, but Ulrich and Yumi get trapped inside. Ulrich tells them to get to Lyoko and deactivate the tower, telling them it was their only hope to escape. Aelita and Odd then leave the house, where Aelita has another vision of a passageway that leads to the sewers. Her theory is proven correct, surprising Odd that she knew about it. From there, they make it to the Factory and are soon sent to Lyoko.
While inside the boiler room, Ulrich and Yumi are slowly passing out from the heat. As the intense heat begins to get to them, Ulrich questions Yumi's relationship with William, who insists he is only a friend as they gradually begin to lose conciousness. Aelita and Odd come across trouble getting to the tower, but finally succeed in deactivating the tower. Jeremie launches a return to the past just before Ulrich and Yumi are about to die from the heat.
Back at the school after completing their assignment, Jeremie asks Odd how his assignment with Ulrich went. Odd says it went fine, but that he had to keep dragging Ulrich away from William and Yumi saying, "Going back in time, didn't change anything there". Ulrich, during this, is watching Yumi say goodbye to William from the corner of his eye, but looks away just as she approaches the group.
Jeremie then gives a report about the Hermitage, saying it has gone back to being a regular abandoned house. Aelita comments on the strange visions that she kept having while at the house, and Odd mentions the underground passage that she somehow knew about. As she thinks back to the Hermitage, Aelita says it was like she had already seen the house before like in a dream. Yumi remarks that it's "a new mystery" for them to solve.
Jeremie then tells Aelita that he got a gift for her, showing her a small gift wrapped box. Aelita opens it to see a pink cell phone as Jeremie explains how they can now maintain contact with each other. Aelita happily hugs Jeremie as Odd says that she's "a regular school kid now".
- The original French name for this episode is Nouvelle donne.
- This is the first appearance of the Tarantula.
- First appearance of William.
- First appearance of Franz Hopper (in Aelita's vision and the ending credits).
- First use of the Overwing, the Overboard, and the Overbike.
- Several scenes from season 1 (On Lyoko and Earth) can briefly be seen in season 2's intro.
- This was the first episode of Season 2 released in book form. The book was only released in French.
- Aelita is in her season 2-3 attire when being led out from the house by Franz Hopper.