Code Lyoko (2003)

Episode Overview

After William joins the team, a chain of events leaves him and Aelita as the only defenders of Lyoko's core. During William's inaugural mission, Xana seizes control of him using the Scyphozoa, turning him into the leader of a vast army targeting the core. Despite their relentless attempts, the group fails to prevent the possessed William from obliterating the core, which not only disables the supercomputer but also transforms William into a darker, Xana-infused version of himself. Later, at the Hermitage, as the team grapples with their situation, Jeremie unexpectedly receives a coded message from the internet, sent by the enigmatic Franz Hopper, who has somehow survived Lyoko's destruction.