The episode begins as Odd and Aelita weave through the trees of the Forest Sector on the Overboard. As they are being pursued by a swarm of Hornets, Odd uses his agility and the trees to evade them at the very last moment to make the monsters crash into them, which Aelita believes is "insanity" to do so, but Odd just says it's more fun to destroy monsters in that way. Suddenly, another Hornet is destroyed by a passing Tessen Fan, which returns to Yumi, who is flying alongside them on the Overwing. On the ground, Ulrich is being followed by two other Hornets. He hits the brakes on the Overbike and slashes them with his katana. Another Hornet swoops in and destroys the Overboard, forcing Aelita and Odd to jump and land not far from the activated tower. Odd stays behind to fight off an incoming squadron of Hornets while Aelita runs to the tower. Aelita hops across tree trunks to get to the tower on the small island surrounded by a pond, but the Scyphozoa is blocking her way. Yumi then swoops in on the Overwing and slices off the Scyphozoa's tentacles, allowig Aelita to deactivate the tower. After a successful mission, Jeremie announces to the group that he is starting up a return in time. The others ask why, seeing as X.A.N.A. hasn't even attacked Earth yet and return trips are known to strengthen the latter. Jeremie answers by saying he knows what he's doing and activates the program anyway.
At school, Aelita, Odd, Ulrich, and Yumi stand by the vending machine. They talk about Jeremie's increasing arrogance. Jeremie walks over to the vending machine and they ask where he was. Jeremie cockily responds, "In my room, why? Is there a law against it?" Then, the bell rings and everyone goes to class.
In Mrs. Meyer's class, Jeremie daydreams of walking in a white hallway that is being covered by darkness. Disoriented, Jeremie asks Mrs. Meyer if he can go to the infirmary. At lunch, Odd, Ulrich, Yumi, and Aelita realize that Jeremie missed both History and Gym class. Aelita leaves the cafeteria to go look for him. She walks into Jeremie's room, finding him typing away at his computer. Jeremie berates her, telling her that he's been working on Aelita's antivirus, which is very important to him and to her. But when Jeremie is about to confess something to Aelita, the Superscan detects an activated tower and Jeremie declares, "You see?! I told you X.A.N.A. never takes a break!"
At the cafeteria, Yumi gets a call from Jeremie, who tells her that X.A.N.A. has launched another attack. As they get up to leave, one of the cafeteria workers, Rosa, tells them to sit down and starts throwing plates at them. Yumi quickly deduces that she has been possessed by X.A.N.A.. The three duck below their table and Yumi tells them to cover her as she will try to sneak out to the Factory. Odd and Ulrich get up and start throwing plates at Rosa to cover Yumi's escape. Yumi gets to the Factory and she and Aelita are both virtualized onto Lyoko's Mountain Sector.
The girls see the activated tower, but eighteen Kankrelats are blocking the path. As they hide behind a boulder, Jeremie brings up the Overwing. At the cafeteria, Rosa has picked up a food cart and is about to hurl it at the boys. On Lyoko, Yumi uses her Telekinesis to toss a giant rock over several Kankrelats and uses the Overwing to drop off Aelita at the activated tower. Aelita deactivates it and Rosa drops the food cart and collapses. Odd tells Jeremie on the phone, "Jeremie, I think this calls for a return to the past. Don't you?" Jeremie then activates the return in time again. At the vending machine, the gang wonders why Jeremie hasn't come yet. They go to his room, only to see him lying unconscious on the floor.
At the infirmary, Jeremie appears to be in a coma, but is dreaming. In his mind, Jeremie is walking along a white hall as darkness from behind him races forward. He tries to outrun it, but it overtakes him, leaving only the white light in the distance. Aelita and Odd go to the Factory while Yumi and Ulrich go to Jeremie's room to look for clues. Ulrich comically says that he hasn't found anything except the fact that Jeremie still wears underwear with kangaroos printed on them. On Jeremie's computer, Yumi tries to access a file called "My Journal", but it's restricted. At the Factory, Aelita can't find anything wrong with the returns to the past. She then gets a call from Ulrich, telling her to come back to Jeremie's room.
Aelita manages to bypass the restrictions on Jeremie's "My Journal" file, revealing six video clips. She clicks on the first one, bringing up a video log of Jeremie. In it, Jeremie explains that he decoded another part of Franz Hopper's diary, finding a way to exponentially increase his intelligence, using the unfathomable power of the return trips. He then shows a Neuronal Headset, which he uses for this. Then, Aelita accesses yesterday's log entry. In it, Jeremie says that his mental and physical health is deteriorating every time he uses the headset, but he is unwilling to stop, so close to success. Odd, Ulrich, and Aelita go to the Factory while Yumi goes to make sure that X.A.N.A. doesn't attack Jeremie.
Outside the Administration Building, Jeremie is put into an ambulance. One of X.A.N.A.'s ghosts enters the ambulance and starts it up just after the driver exits the vehicle to sign a few papers for the principal. Yumi gets there, just in time to see the renegade ambulance drive off. She starts pursuing the ambulance on a bike. At the Factory, Ulrich, Aelita, and Odd arrive to Lyoko's Ice Sector. They start running towards the activated tower. Yumi almost reaches the ambulance's door, but the ambulance speeds ahead, leaving Yumi behind. She rides her bike down a stairway and catches up with the ambulance. She opens the door and gets in, calling out to an unconscious Jeremie. In Jeremie's mind, Yumi's voice brings Jeremie out of the dark hallway and he wakes up. They plan on stopping the ambulance before they get off. Unfortunately for them, the ambulance is speeding toward the river.
Meanwhile, on Lyoko, a group of five Tarantulas confronts the Lyoko Warriors. Ulrich comes up with a plan. They fire around the monsters, causing cracks to appear in the ice. The cracks widen into fissures, with water between them. The ice breaks apart and most of the Tarantulas drown, leaving two out of five left. In the ambulance, Jeremie smashes the window with an oxygen tank and Yumi gets into the driver's seat. Unfortunately, nothing in there is working. The ambulance crashes through the security railing and plunges into the river.
Ulrich is devirtualized by a laser bolt and heads up to the lab. Odd causes a Tarantula to slip off its ice piece and drown, but is devirtualized by the remaining Tarantula. In the lab, Ulrich responds to a desperate call by Yumi, who tells him that the ambulance is sinking. Aelita uses her Creativity to make an ice arch that spans the icy water. She slides across it and enters the activated tower, deactivating it. In the ambulance, water is seeping in. The only thing that will save them now is another return trip. Following Jeremie's instructions, Ulrich initiates a return to the past.
The group goes to Jeremie's room to see him smashing his headset. He tells them that most of the calculations he made were wrong. Jeremie admits that Franz Hopper's discoveries are out of his league and he'd better be careful the next time he tries out one of Hopper's experiments.
- The original French name for this episode is Tentation.
- This episode, despite being numbered as 38, and chronologically taking place before episodes 39-49, it aired considerably later than all of them. It aired in conjunction with episode 50, Contact.
- When Odd and Ulrich are being attacked in the cafeteria by a possessed Rosa, Ulrich makes a reference to the cartoon Looney Tunes, saying "Now I know what Tweety feels like against Sylvester!"
- This episode was released in book form, but only in French.
- This episode marks the first appearance of Odd’s special ability to materialize a shield.
- Before the first return in time, Odd asked Jeremie if he was sure, but Ulrich's audio card made it seem like he was talking.
- When Ulrich is asked to perform a return to the past, he states that he has no idea how to activate it despite the fact that he successfully launched a return trip three episodes earlier in The Chips Are Down.
- When Yumi and Jeremie are trapped inside the ambulance with Yumi in the driver's seat, she puts on a seatbelt, but when they crash in the water, her seatbelt is off.
|Code Lyoko: Season 2|
|New Order | Uncharted Territory | Exploration | A Great Day | Mister Pück | Saint Valentine's Day | Final Mix | Missing Link | The Chips Are Down | Marabounta | Common Interest | Temptation | A Bad Turn | Attack of the Zombies | Ultimatum | A Fine Mess | X.A.N.A.'s Kiss | Vertigo | Cold War | Déjà Vu | Tip-Top Shape | Is Anybody Out There? | Franz Hopper | Contact | Revelation | The Key|
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