Kilobyte pays Lord Fear a visit. In exchange for Fear's assistance defeating Ace Lightning and furthering his plans to conquer the mortal world, he gives him an upgrade. Meanwhile, Chuck and Mark decide to find out what Kilobyte is up to, alone.
One day at school Mark Hollander encounters a mysterious girl he knows nothing about. She says that he can trust him but can he really? She also claims that she is a part of the war between Lord Fear and Ace Lightning. Can Mark trust her? Also what is the secret that Lord Fear wants from her so badly.
Mark faces the prospect of returning to school and Ace tries to convince Fear that they need to work together in order to defeat Kilobyte.
Aelita and the TD Lyoko Warriors believed that they were the only ones battling evil on the digital plane but when a boy named Mark Hollander arrives in France he unintentionally brings with him forces beyond anything they have seen before that force them into a battle that could light up the skies of the Earth and threaten all of humanity.
Kilobyte is nearing escape from the game and Rick is struggling to keep him contained; the programmer needs the help of a superhero to keep him there.
Set after the second season. Chuck searches to bring Lady Illusion back from the game, Lord Fear and Ace try and settle a score, and Ace lets out they've all just come from a video game designed to entertain mortal children.
This time, Hollander had gone too far.
Raven reflects on how it all went wrong.