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 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 tells him how he can never figure his relationship with Yumi out and asks if they were 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. Saying that he wouldn't consider himself a "rebel" he's just "really rebellious", admitting 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. At the academy, Jeremie gets to his laptop in time just 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 that Jeremie would call Yumi himself. Jeremie calls Yumi as William continues to flirt with her, causing her to take off to join the others.
Aelita is eventually lead to a house known as the Hermitage. There, she has even more visions and is attacked by X.A.N.A..
Once the others arrive to find her, they learn that X.A.N.A. has possessed the house and uses the variety of objects in it to attack them. During the attack and evading X.A.N.A's attacks them, they find Aelita unconscious in a sauna down in the basement. Just as they get to Aelita who becomes conscious, she warns them that it was a trap just as 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 a vision of a passageway that leads to the sewers. Her theory is proven correct, surprising Odd that she knew about it.
While inside the boiler room, Ulrich questions Yumi's relationship with William, who insists he is only a friend as they slowly begin to pass out from the heat. Aelita and Odd come across trouble getting to the tower, but finally succeed in deactivating the tower, and Jeremie launches a return to the past just before Ulrich and Yumi 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" while looking at Ulrich is watching Yumi say goodbye to William from the corner of his eye but looks away just as she approaches the group. Jeremie then tells Aelita he got a gift for her, showing her a gift wrapped tiny box. Aelita opens it to see a pink cell phone.
- 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.