Code Lyoko centers on four children who travel to the virtual world of Lyoko to battle against a sentient artificial intelligence named XANA, with a virtual human called Aelita.

Jérémie, Aelita, Yumi, Ulrich, Odd and William return to their daily lives as students of Kadic College. But XANA, the multi-agent program that had become their mortal enemy and that they had managed to destroy in their previous adventures, reappears. The Lyoko Warriors reactivate the supercomputer in order to return to Lyoko, discover the reasons for this reappearance and put an end to it before the Earth is threatened again.