After finally defeating XANA, our heroes gather again to shut down the super computer, but find it hard to put an end to their lives of adventure. They may not have a choice though, when Sissi reveals their secret to the school headmaster.
In the ultimate battle against XANA, our heroes work with Franz Hopper to destroy the evil super computer forever. But first they must face everything XANA can throw at them, and Franz Hopper sacrifices himself to save the warriors.
Our heroes return to Siberia to free William from XANA's clutches, but first they must defeat the Kolossus and an army of robots. They better hurry too, because William's parents are visiting and his clone won't fool them for long.
Odd and Yumi travel to polar Siberia on a mission, only to be confronted by William who has been sent by XANA to stop them. Meanwhile, Ulrich and Aelita confront XANA's latest creature, the massive Kolossus.
XANA uses the school's cell phone antenna to spread a virus causing phone users to become evil zombies, including Odd's parents, who are visiting. Our heroes travel through Lyoko to the mountains to stop the virus and reverse its effects.
Aelita's secret past is in danger of being revealed when Sissi gets a hold of an old photo of Aelita with Franz Hopper. Meanwhile, Jeremy needs the picture because of the mathematical formulas written on the blackboard in the background.
XANA kidnaps Aelita just before her big night deejaying at the Subdigitals' concert. While her friends battle to save her in the virtual world, Odd is busy looking for an extra ticket that he promised to a girl he wants to impress.
Jeremy's cousin Patrick visits and problems arise when Patrick lets Herve look at Jeremy's computer. Our heroes' mission is soon compromised and Aelita's fake identity is uncovered. Only a trip back in time can fix this situation.
Yumi and Odd travel into outer space on a mission to destroy a newly-discovered super computer with a dangerous defense system. Meanwhile, Yumi's family cares for Odd's dog during a surprise dorm inspection at school.
Odd's dog Kiwi is banished to the factory after another incident at the dorm. Meanwhile, XANA takes control of Jeremy's robot dog, Kiwi2 and turns it into an attack dog, so Aelita travels into Lyoko to deactivate the tower controlling it.
The beautiful new exchange student is very interested in Odd and he attempts to woo her by showing her the super computer. But when she touches the computer, it creates a series of problems with disastrous results for those in Lyoko.
Jeremy wins a ride in the back of a military jet fighter, but when XANA takes control of the jet's computer - and its missiles, our heroes must defeat the super computer in the virtual world before the plane and its weapons hit the school.
Odd breaks a mirror, causing bad luck to follow him everywhere, including Lyoko. As the heroes make another trip to the desert, they hope the bad luck is behind them when face off against an army of XANA's Kankrelats.
While everyone is gone for the winter holidays, Aelita stays behind to watch for XANA. But she receives a message from her long-lost father inviting her to join him in the virtual world, and she accepts, realizing too late that it's a trap.
Our heroes travel to the desert to destroy a hidden super computer but their trip is cut short when the real William arrives in the computer lab. Meanwhile, Jeremy tries to prevent William's clone from being discovered by Milly and Tamiya.
Odd takes his dog into Lyoko and ends up with uncontrollable dog behaviors in the virtual world. While Jeremy tries to separate them, Yumi battles a real world motorcycle gang possessed by XANA and Ulrich and Aelita battle William in Lyoko.
Code Lyoko Season Three
Code Lyoko Season Two
Code Lyoko Season One
Code Lyoko Season Four