Odd decides to start a music band with his friends. But Jeremy can't play, so they try to hire a drummer. In the end, the best drummer they can find is Nicholas (Sissi's blond-haired crony). As the group argues over whether or not to let Nicholas join the band (Ulrich and Yumi: Pro-Nicholas. Odd: Anti-Nicholas, Pro-Naomi), Jeremie alerts them that XANA is planning to overload a pylon and send this massive electric current through the telephone wires to blow up a nuclear power plant. Just in the nick of time, Aelita, Ulrich, and Odd stop XANA's plan. At the end of the episode, Odd gives in and allows Nicholas to be the drummer of his rock band.

The day starts off when two girls are talking about Ulrich and then Sissi goes and interrupts and tells the girls that Ulrich is hiding his affections for her. Later, Odd, and Ulrich pull a prank on Sissi, giving her a txt message about a ""true love"". While the prank is being set, people in the town are experiencing difficulties due to a strange virus, now 2 trains are going on a collision course and one of the trains has highly toxic chemicals which can kill the town's population. Yumi cannot contact Ulrich and Odd because they shut off their mobiles. The prank is being set and Sissi opens a shed which happens to be Kiwi (Odd's dog)in there and jump om Sissy. Then Od gets in trouble after bringing Kiwi on the campus. Yumi finds the 2 and try to go to the factory, but Odd is stopped by Jim and is carried over to the principal. Now to help Aelida fix Xana, they will need everyone in the group, where is Odd when you need him?

Ulrich and Jeremy are doing graffiti on a wall on campus while Kiwi wakes up Jim. When Jim passes Ulrich and Jeremy, Ulrich gets away, but Jeremy just stays there and gets I'm trouble and has to stay in the campus over vacation. Sissy is being suspicious of Jeremy and thinks that he wanted to get in trouble. She asks her father to stay over the campus over her vacation, while she sorta spies on Jeremy. Jim is telling Jeremy to wash off the graffiti, then leaves while Jeremy gives Sissy the sponge and tells her (while mimicking Jim) to wash off the paint and later once again gets in trouble with Jeremy. Meanwhile, Xana has attacked again, this time spilling two toxic chemicals creating hazardous smoke. Sissy claims that she saw the smoke with arms and bumps into Jim who later finds the smoke after not believing in Jeremy and go into a small room where there is no vent and if they try to open the door, they can die. How will Yumi, Aelita, and Odd save the world and how will Ulrick find

Ulrich is fussing over a mysterious letter found slipped under his door one night... a love letter signed by Yumi! Meanwhile, XANA infects a hive of bees and is using it to attack our heroes. Ulrich struggles with his feelings and how to tell Yumi how he feels about her; that is, if he can figure it out himself, and saving the day from XANA in an episode of life and death.

A student named Milly seeks the comfort of her teddy bear after being embarrassed and ostracized due to her young age by Sissi, the school's bully/diva. Milly believes that her teddy is the only one that she can turn to for comfort and support. A corrupted super computer known as X.A.N.A. enters the real world by possessing the bear. In a quest to strike and destroy his enemies, the X.A.N.A infected teddy bear increases to an enormous size. No one is safe as this monstrosity creates a path of destruction.

Sissi has found something very special and dear to Ulrich, his diary! Unfortunately the diary contains some information on X.A.N.A. and Lyoko. Sissi decides to use this as a means of blackmail to get with Ulrich. Later Odd, Ulrich, Sissi, and some of the other students are going to a pool, the bus that their riding in is X.A.N.A.'s next target. He wants to ram the bus into a chemical plant. Now the team must head to Lyoko to help Aelita get to the tower to save the students and the rest of the city.

Jeremie mysteriously loses contact with Aelita. The same day, a new student named Taelia (who looks alot like Aelita) arrives at school. Jeremie is convinced that Taelia is Aelita devirtualized, but the others aren't too sure. Meanwhile, XANA posseses an ancient samurai armor that Yumi brought for a project and goes out to kill Jeremie and the others. Jeremie heads to the lab, taking Taelia with him, hoping that she'll get over her ""amnesia"" and remember that she is Aelita. But what happens when Jeremie discovers that he wrong?

After a quick game of soccer, Yumi heads home for the night, but Odd and Ulrich head in for dinner, and Jeremie is already there. He decides to check on Aelita, and Yumi ends up following him instead. But, while scarfing the desserts the others left behind, he and Ulrich get caught up in a shocking Xana trap. Not only is the lunchroom electrified, the roof may fall in at any time. Even the combined power of the eight kids trapped inside - including Odd, Ulrich, and Sissy - can only delay Xana for a short time. Will Yumi be able to get Aelita to the tower before the room becomes a final resting place for our heroes?

Both Herb & Jeremy are in a robot competition Herb with ""Iron Sissy"", and Jeremy with ""Kiwi 2."" Herb cheats by launching a gear from Sissy to destroy ""Kiwi 2."" Meanwhile, Xana's latest plan, using the factory to built a robot. Ulrich & Yumi get help from Herb in slow down Xana's robot. Jeremy discover that Xana robot had built in the factory and messed with computer that goes to Lyoko. Jeremy fixes the super computer, and Odd helps out Alieta in Lyoko. After the time reboot, Kiwi 2 dodges Herb's gear to win the contest.

Well, it starts off as Yumi wanting to have a party at her house. Of course, Odd jumps into action, and says that he has the Deejay problem all solved, they weren't going to listen to Sissy's music. But, oddly, Jeremy couldn't get a connection with Lyoko. Later, Odd and Ulrich are having sliding contests across the floor, but soon, a picture of the Deejay Odd was getting fell on the floor. Ulrich and Jeremy saw is and they asked who it was. Odd said it wasn't important, and he had some stuff to do. Later, again, Odd saw Samantha, the Deejay he was getting, and obviously, he happened to know her. They got into the Comp. Lab, and Sam wanted to take the most powerful laptop there. Jim went in and saw Odd holding the laptop. He scolded Odd, and he ended up getting out. But, they saw Xana attacking. They went to go and rescue Samantha, as she was still in the lab. Yumi and Jeremy went to the factory. Ulrich and Odd saved Samantha, but when Yumi got to Lyoko, she was materialized as soon as

When the school holds a concert in the gym, William accidentally drops a mixing board for the DJ contest. Odd offers to fix it, and tries to get Jeremie to help. Jeremie is busy, so Aelita offers her help. She easily fixes the device, and finds that she is quite talented in using it. The school is holding its finals, as well, and Odd finds that he is not prepared in the least. Meanwhile, Xana possesses Jim and takes Aelita to the factory in order to deliver her to the Scyphozoa.

During the school physicals, Xana possesses the school nurse, Yolande, and has her kidnap Aelita. The rest of the group beats her to the factory, but has no way to get Aelita from the far more powerful nurse. Having no other choice, Jeremie decides to test out an experiment which will give a person the same powers as one possessed by Xana. To do this, he has to activate a tower like Xana. Jeremie's towers turn green instead of red. Odd volunteers, and is enhanced by a ghost of Jeremie's design. This allows Odd to fight the nurse effectively while the others deactivate the tower. This fortune doesn't last, however. Xana is able to take over Jeremie's tower, reversing the effect of the ghost to drain Odd's energy. And on Lyoko, Xana makes everything invisible. Now the group has to deactivate not only the original tower, but the tower that's draining Odd's energy.

When all the student's cell phone goes off in class, it starts Sissy on a petition to save her cell phone--but it's goes awry when Odd breaks into the school's office's locker to get his, Ulrich, & Yumi's cell phone. It turns out that X.A.N.A. is trying to get out board a highly powerful miltiary satellite in space. X.A.N.A.'s target turns out be our heroes.

Jeremie learns that he has to take a test. If he passes, he'll get transfered to a new school and nobody will be able to stop XANA. Speaking of which, XANA takes control of a pack of rats. The rats attack the school and makes it nearly impossible to move around. Ulrich, Yumi, and Odd get Jim, Sissi, and everyone else to the roof and then proceed to the lab. Ulrich and Odd are virtualized, while Yumi controls the supercomputer. Does the team stand a chance with Jeremie temporarily gone?

After a trip to the Carthage Region, Jeremie believes he has the data necessary to cure Aelita's virus. While the two work on the cure, Odd, Ulrich, and Yumi go to a rock climbing contest. Odd races against Hervé, who is no match for Odd. William then goads Ulrich into racing, despite his obvious reluctance. During the race, Ulrich gets dizzy and falls. Yumi realizes that he must have vertigo. Ulrich, embarrassed, runs off. Meanwhile, Jeremie finds the anti-virus and gives it to Aelita. Despite some problem with the application, it seems to work. However, this does not last. An error in the anti-virus causes her to turn invisible. On top of that, she can't enter the towers on Lyoko, making it impossible for her to stop Xana's latest attack, which is a possessed pack of wolves targeting Odd, Ulrich, and Yumi.

Aelita's visions become a problem once again, but not the same visions as before. This time, she has visions of her and Franz Hopper being chased by government agents. The visions come even when she's awake, causing her to lose consciousness while at the pool. Wanting to know the source of the visions, she heads to the Hermitage to learn more about them. Jeremie discovers that Xana is causing the visions through her link to the supercomputer. During the mission to stop them, Aelita breaks away and heads to The Carthage Region, determined to discover the source of the visions.

After reading about a dead man named Leon Corbe, who died during the construction of Kadic, Sissi decides to hold a séance to communicate with him. She manages to convince Ulrich to attend. During the séance, one of Xana's ghosts appears in the form of a four-armed monster. At first, it seem docile, but quickly gets angry and attacks. Ulrich leaves Sissi with Odd while he goes to tell Jeremie. Jeremie can't find an activated tower, which seems wrong considering the situation. As Jim patrols the hallways, he is picked up by an invisible object. Jeremie, Odd, and Ulrich arrive to spray it with a fire extinguisher, confirming that it's a ghost and implying that the super scan is broken. With the ghost on the loose, the group heads off to the factory. After they arrive, Aelita, Odd, and Yumi head to Lyoko. Odd looks for the tower while the other two head to The Carthage Region to fix the super scan. Meanwhile, Jeremie and Ulrich are left to deal with the ghost.

Xana attacks the Lyoko warriors by possessing a large amount of food. At the same time, he bugs up The Mountain Sector by rising the digital sea, but Odd and Aelita go to Sector 5 to stop him. Xana also mounts an attack on Lyoko's core at the same time.

When Odd complains that he doesn't have any cool powers on Lyoko like his friends, Jeremie designs him a teleportation power. It works, but ends up leaving duplicates of himself in the location he teleported from in The Mountain Sector. After trying it twice, Jeremie devirtualizes Odd to find out what went wrong, accidentally creating three clones. Meanwhile, in the real world, Xana attacks using a mysterious smoke that turns anyone it hits to stone. One of Odd's copies gets turned to stone, so the other two Odds must retrieve him before they become unstable and disappear.

Jeremie is working on the materialization program, and finally gets it. Jeremie wants to matierialize Aelita, but realizes that preparations need to be made. That night, Xana possesses two bulldozers and starts to destroy the factory. Odd and Yumi go into Lyoko where she falls into a virtual black hole. In order to save Yumi's life, Jeremie has to choose between either materializing her or Aelita.

The episode starts with Jeremie still trying to materalize Aelita. He calls the team to the factory to show them his latest development: a strand of her hair that he has materalized into a test tube. Unfortunately, he didn't realize that he pressed one button too many, and thus screwed up Aelita's programming by adding in a whole lot of bugs. The result is that, immediately after she successfully enters the code (LYOKO) into a tower, she will be formatted - as in, deleted. And of course, as Jeremie is trying to literally work out the bugs, Xana attacks by putting out shockwaves to shake things up, putting Odd, the two junior journalists, and Kiwi in danger. But is Jeremie willing to allow Aelita to be deleted in order to save his friends?

After seeing laughing gas in Science class, Team Lyoko has to see it again - working for Xana. While working for Sissy in a school production of Romeo and Juliet, Ulrich and Yumi are overcome by the gas, and both Jeremie and Odd get a bit too much at the factory. Of course, this results in a data transfer error, leaving Odd bearly able to walk, much less fight off Xana's hordes of monsters. With Aelita flying solo and three of the team in critical condition, will the crew literally die laughing?

When Ulrich learns that Yumi might have to go back to Japan because her father lost his job, he can't accept losing her. After hearing the lottery numbers on the radio though, he gets an idea. Using a return trip, he is able to get a ticket with the winning numbers and give it to Mr. and Mrs. Ishiyama. When the others find out, they kick him out of the group until they can figure out what to do. To make matters worse, Xana activates a tower and possesses Nicolas. On top of that, he creates an army of Krabs to guard it.

After a malfunction and a little bug with the regular materialization program, Odd and Yumi are bugged up, ending up in each others' bodies. Even worse, their atoms start splitting after a while due to being dematerialized, even on Lyoko. The gang has to go to Lyoko and fix the problem before Odd and Yumi disintegrate and disappear forever, but it's not easy when Xana tries to stop them.

When Xana hacks into a weapon's manufacturing computer network and leaves a paper trail pointing to Jeremie, government agents arrive at the school looking for him. Then, the whole gang arrive at the factory. When they end up tracking Jeremie to the factory, Xana possesses them for an attack on the supercomputer itself in The Ice Sector, and in The Mountain Sector.