While on her first science field trip with the rest of the gang, Aelita begins to experience mysterious visions that draw her to an abandoned house called the Hermitage. In nervous preparation to reveal to Yumi how he feels about her, Ulrich becomes a little jealous when he sees her hanging around a new student named William. Written by Nicky

Haunted by a recurring nightmare and having a difficult time adjusting to her new life in the real world, Aelita decides to return to Lyoko. Meanwhile, Jeremie does some background research on the hermitage, and discovers a connection between it and Kadic. As the gang continues to search for answers to their many questions, a new mystery appears out of nowhere. Written by MattB

After a couple of late nights, Yumi's parents start to get suspicious and she is forced to sit out the battles on Lyoko for a while. Odd, Ulrich, and Aelita return to Sector Five to search for more information on Aelita's anti-virus program. Written by Logan82

The gang is forced to continuously relive a day after X.A.N.A. is able to take control of the time-traveling mechanism. Meanwhile, Sissi attempts to blackmail Jeremie with a recording that she made of him conversing with Aelita about her true identity. Written by MattB

Aelita begins to experience her recurring nightmare while she's still awake, which leads to further investigation of the hermitage. As they continue to uncover more clues to this growing mystery in Lyoko, a deadlier X.A.N.A. infiltrates the group in order to get to Aelita. Written by MattB

In Aelita's room, she is having yet another bad dream. The man in red leaves a present outside her door. This gift from this stranger on Valentine's Day makes Aelita happy and Jeremie jealous. Meanwhile, Jim has caught the strange man. It turns out that he's been possessed by XANA. At the same time, gifts from Sissi and William place Ulrich and Yumi in a similar and awkward position. Things are not what they appear to be. Written by MattB

After repairing William's turntables and showing some mixing skills, Aelita is invited to DJ at Kadic's techno dance party. Spending her time in preparation for this event results in an argument between Aelita and Jeremie over what is important in life. Meanwhile, X.A.N.A. uses the school dance to stealthily go after Aelita. Written by MattB

In preparation for another trip to Carthage, Yumi is attacked by the Scipizoa and drained of a vital component needed for materialization into the real world. Now Yumi is stranded in Lyoko as the gang races against time to find a way to bring her back before X.A.N.A.'s next attack. Despite Jeremie's objections, Aelilta decides to sacrifice herself in order to save Yumi. Meanwhile, to prevent Yumi from getting in trouble with her parents and the Kadic administration, Sissi agrees to pose as her for the school pictures. Written by MattB

Yumi reveals to her friends that there is a possibility that she might have to go back to Japan as a result of her father losing his job. The thought of Yumi no longer being around proves to be too much for Ulrich. He decides to risk making X.A.N.A. stronger and his friendship with the rest of the group to prevent this from happening. Written by MattB

Using the concept of marabounta and some of Franz Hopper's research, Jeremie creates a program to search and destroy X.A.N.A.'s monsters. It appears to be a success until it targets Aelita and all of Lyoko for elimination. Meanwhile, Ulrich embarrasses himself while trying to upstage William for Yumi's attention. Written by MattB

The battery which powers the super-computer is running out of fuel, so XANA possesses a criminal to steal some uranium. Although our heroes want to stop him, they are forced to help XANA since Aelita's survival is also at risk!

After XANA's attack, Jeremie insists on a return trip, regardless of the fact that XANA didn't even cause any damage. When questioned, he gets defensive and angry, insisting that it's necessary. Further questioning on the matter leads to the same result. After the next return trip, Jeremie is found unconscious in his room. Yumi and Ulrich go searching through Jeremie's room to see what they can find about Jeremie's problem. Upon decoding a video diary that is stored on his computer, they learn that he had been using the return trips to increase his own intelligence. When he's about to be taken to the hospital, XANA attacks, possessing the ambulance and driving it towards the river with Yumi with him. Now the others have to save Jeremie and deactivate the tower without Jeremie's help.

Ulrich and William battle to impress Yumi during Drivers Ed at school, but they must find a way to put aside their differences and work together when XANA unleashes an army of Krabes in the real world.

XANA uses Kiwi the dog to spread a virus which turns people into zombies. As panic spreads everywhere, our heroes find a way to escape and get to the factory, in order to deactivate the tower before it's too late!

After XANA possesses Jean-Pierre and kidnaps Odd and Yumi, he gives Jeremie an ultimatum: deliver Aelita to the Scyphozoa or sacrifice Odd and Yumi. However, Jeremie and Aelita go to Sissi for help after being questioned by the police. Sissi agrees to be temporarily part of the group to help save her father and stop XANA.

After another successful mission on Lyoko, our heroes rematerialize, but the program has malfunctioned and switched Yumi and Odd's bodies. It seems funny at first, until they realize if not reversed, they could both disintegrate for good.

Love fever and jealousies have taken over the academy and threaten to separate our heroes forever. But even when they discover it's XANA's evil plan, can they overcome their jealousy in time to save Aelita from the Scyphozoa's clutches?

After a trip to Sector Five, 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.

XANA takes control of the weather and sends temperatures plummeting so low that any outdoor exposure could cause breathing problems. Our heroes must come up with a plan to get to the factory and enter Lyoko to thwart their enemy.

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 Sector Five, determined to discover the source of the visions.

During the school physicals, XANA possesses the school nurse, Yolanda, 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 in the Mountain Region, XANA makes everything invisible. Now the group has to deactivate not only the original tower, but the tower that is draining Odd's life energy.

After hearing strange noises, Sissi conducts a sÃfance at the school. XANA takes advantage of this and sends out a ghost, sending panic across the campus. Our heroes know this is the work of XANA, but can they deactivate the tower in time?

Jeremie discovers five activated towers and gathers the group to take care of them. However, when they arrive at the factory, they find a man at the interface, deactivating the towers as if it were a simple matter to do so. When questioned, the man claims that he's none other than Franz Hopper. However, something seems off about this convenient arrival. Franz says that the scanners cause cell degeneration, and blames it and the destruction of his diary on Jeremie. With everyone except Aelita angry at him, Jeremie calls his father and asks to be withdrawn from Kadic in favor of a school for gifted students - but after he hangs up, while pondering his dilemma, he realizes that there is something inherently wrong with Franz's explanation.

During a short film made by Odd and starring Sissi, Sissi seems to be possessed by a ghost. She does not act as expected, however. Instead, she starts speaking in some strange language, focusing on Jeremie as she does. She is taken to the infirmary as a result. Later on, she walks into Jeremie's room and writes some code on a piece of paper. Jeremie translates the code, revealing a message stating a desire to help. Sissi is sent to the hospital after this, forcing Odd and Yumi to go there and collect her. On a trip to Lyoko, Aelita and Ulrich discover a white tower. XANA isn't happy about the tower, and sends Megatanks to shut it down forcibly. At the same time, it activates a tower and possesses a nurse at the hospital to do the same to Sissi. Odd and Yumi are able to prevent the nurse from doing so. They bring Sissi to the factory to finish the message she started earlier. She manages to type most of it out before XANA succeeds in shutting down the white tower. After XANA's tower is...

After the retrieval of vital information from the fifth sector, the gang returns to Lyoko so that Aelita and Jeremie can decode Franz Hopper's diary. X.A.N.A. sees this as a perfect opportunity to deceive the group and sabotage the mission. Written by MattB

With the end of the year school dance approaching, the gang sets out on a final mission to retrieve a vital component needed to cure Aelita. Tormented by the startling revelations concerning Franz Hopper and the origins of Lyoko, a troubled Aelita takes drastic action to finally rid the world of X.A.N.A. Written by MattB