XANA gains the ability to go back in time and our heroes discover this power also makes him stronger, to the point where he can now control human beings. After XANA possesses Sissi, the heroes realize they must take action quickly.
Watch Now:AmazoniTunesAelita receives a necklace which she believes is from Jeremy but is actually a poisoned gift from XANA. She puts it on and becomes powerless to resist the urge to go to Lyoko where XANA's trap awaits her.
Watch Now:iTunesXANA possesses the school nurse during the annual Kadic physical fitness tests and she kidnaps Aelita. In order to prevent her from turning Aelita over to the Scyphozoa, Jeremy activates a tower of his own, but XANA is ready for them.
Watch Now:AmazonAfter an epic battle, William reappears at school, but his unusual behavior has attracted the attention of Sissi, editor of the school paper. William, who is clearly still under XANA's control, kidnaps Aelita, taking her back to Lyoko.
Watch Now:AmazoniTunesAfter Jeremie fails zet again to materialize Aelita, a student Taelia arrives at school that looks exactly like her. Jeremie is convinced that it must be her. The others aren't quite as convinced, but Jeremie insists that the materialization process must have caused her to lose her memory. X.A.N.A. possesses the samurai armor that Yumi brought to school and sets it on the group to chase them.
Watch Now:iTunesFamous director James Finson announces that he plans to make a movie in the city, using the factory as their primary location. Ulrich tries to convince Finson that making a movie there would be a bad idea. X.A.N.A. possesses the alien monster prop and uses it to capture Ulrich and Sissi and use them as bait for the others.
Watch Now:AmazoniTunesAfter Jeremie and Ulrich paint funny graffiti of Jim on aschool wall, Sissi overhears him talking about X.A.N.A. She gets her father to let her stay there during the vacation so she can discover the group's secret. X.A.N.A. takes the opportunity to possess several barrels full of poison and turns the poison into a deadly, living gas.
Watch Now:iTunesWhen a vicious dragon steals the food reserves from a group of dwarves, Gwizdo and Lian Chu take the case. But when they run into unexpected problems, the dwarves decide to turn our heroes into lunch.
In class, Susan teaches the class about nitrous oxide, more commonly known as laughing gas, and its effects. It can be dangerous if not neutralized by water quickly. During a school production of Romeo and Juliet, X.A.N.A. possesses the laughing gas in the science room and uses it to attack the gang so they would laugh themselves to death.
XANA tries to destroy all of the surface sectors on Lyoko -- the only way for our heroes to access Sector 5. They need Jeremy's help getting directly into Sector 5, but he's busy running for election to the Academic Council, against Odd!
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