A highly malevolent and rogue artificial intelligence (also referred to as a multi-agent system) named X.A.N.A., bent on world domination, has taken over the quantum supercomputer in charge of the virtual reality/world of Lyoko. If the group is able to get Aelita to the activated tower(s) out of the more than forty scattered about four of Lyoko's five tropical regions, she can neutralize Xana's violently destructive attack on the real world; then the supercomputer can reverse time to just before the attack, leaving no one except the group to remember any of the events that transpired. To complicate the situation, they must do this while ensuring that their classmates and teachers are not killed (because going back in time cannot return those killed by X.A.N.A. to life), and deal with the various personality clashes they have with them at the same time.