Lyoko is a parallel universe to Earth. Odd, Urich, Yumi, and Jeremie found Lyoko in an old empty building. When Jeremie sent Odd, Ulrich, and Yumi into Lyoko, they found Aelita and XANA. XANA is trying to destroy the world. There are 40 towers in Lyoko and when XANA activates one the gang has to find it while battling monsters and trying to keep Aelita safe. When they find the tower Aelita must deactivate it, as she is the only one who can. Jeremie is trying to materialize Aelita (bring her to Earth) so they can shut Lyoko down. If Aelita is in Lyoko when they try to shut it down she will die.