Enjoying their normal lives, Jeremy Belpois, Ulrich Stern, Odd Della Robbia, Yumi Ishiyama and Aelita Schaeffer soon discover that there is trouble still brewing at Kadic Academy. Even worse, the five best friends discover that their old and greatest virtual enemy - the evil, sentient and autonomous artificial intelligence/multi-agent system XANA - is somehow back and even stronger and more dangerous than ever before, as a highly evolved and modified version of itself. XANA now wants to take back its power - source codes that were implanted in the electromagnetic parts of the bodies of Aelita, Odd, Ulrich, and Yumi during the time of its supposed "destruction" in order to gain control over the world network once again. The war against XANA is far from over, and the five Lyoko Warriors are back in action.