William has joined the gang of Lyoko warriors. He can’t wait to go into his first combat to take on XANA and the virtual monsters! The others try to curb his enthusiasm: XANA is a far more dangerous adversary that William can imagine. At that, each of them returns to manage their academic demands. But quickly XANA goes on an attack to wipe out Lyoko once and for all. For one reason or another, Jeremy, Odd, Ulrich and Yumi all find themselves unable to leave Kadic Academy.
Only William and Aelita are able to go to Lyoko to fight against XANA, and so they do. But once William arrives in Sector 5, he lets his bravado get the better of him and ignores Aelita’s advice. As a result, the pair is separated and XANA is able to take possession of the boy. When Yumi, Ulrich and Odd finally make their way to Sector 5, they find themselves pitted against William who has become the super-powerful general of XANA’s army. They must fight against him to spare the Heart of Lyoko from certain destruction… can they do it before it’s too late?
This episode contains examples of:
- Abusive Parents: Ulrich's emotionally abusive father comes to Kadic to berate him about his poor grades, not seeming to care if there's a reason for it and simply assumes his son is lazy and hangs out with the wrong people. Ulrich takes it... until he begins accusing his friends of being a bad influence and he should stop seeing them. At that, Ulrich snaps that his dad hasn't even met them and doesn't even know him as they haven't even talked in a year. He then leaves, declaring that he's done listening to his dad.
- Back Stab: How William devirtualizes Yumi.
- The Bad Guy Wins: XANA is finally able to destroy the core of Lyoko.
- BFS: Willaims' sword is about as big as himself.
- Cool Sword: Williams' giant sword is able to parry laser fire.
- Contrived Coincidence: Jérémie, Ulrich, Odd and Yumi are all preoccupied when XANA attacks the Core of Lyoko, forcing Aelita and the inexperienced William to go alone, with no one to guide them from the computer lab. This allows Aelita and William to be separated and William to be possessed by the Scyphozoa.
- Curb-Stomp Battle: Zigzagged. On Sector 5, William defeats various Creepers effortlessly, however, he's no match for the Scyphozoa. Once under XANA's control, he devirtualizes all the other Lyoko warriors with ease.
- Demonic Possession: William gets taken over by XANA, and becomes a very formidable foe.
- Fetal Position Rebirth: William, after destroying the core of Lyoko, complete with Crucified Hero Shot when he comes out of the position.
- Friend-or-Idol Decision: Samantha doesn't tell Odd that Ulrich left a message for him (a coded message about XANA's attack), so that that the two of them can spend more time together. When Odd does find out Sam hid this from him, he's not happy, and reluctantly leaves her, telling Sam that the thing he has to do is simply more important.
- Hope Spot: A program that Aelita started on the supercomputer finds Franz Hopper on Lyoko and Jérémie tries to materialize him but the core of Lyoko is destroyed before that happens.
- Leeroy Jenkins: William got too caught up in battling XANA's monsters, ignoring Aelita's warnings, and thought he could take on the Scyphozoa. This ends up getting him possessed by XANA.
- Naïve Newcomer: Played for Drama. William blows off Jérémie and Aelita's warnings about how serious fighting is on Lyoko and carelessly disregards them saying how dangerous the Scyphozoa is, treating it all like a video game. This attitude gets him possessed by XANA.
- Opportunistic Bastard: XANA seems to have gotten the idea for possessing William when the gang all talk about it, and he adjusts his other plans accordingly.
- One-Hit Kill: William devirtualizes Aelita, Odd and Yumi with a single hit. The only Lyoko warrior capable of offering any resistance is Ulrich but even he is devirtualized with one hit after William blows his saber out of his hand.
- "Ray of Hope" Ending: The end of this episode marks XANA's biggest victory. His goal is to destroy Lyoko so that nothing can undo his attacks on humanity. At the end of the episode, he not only succeeds but makes William his slave. But, when all hope seems lost, the heroes get a message from Hopper again, hinting that he may have a solution. (In the next season, it is shown that Jeremie is able to use what Hopper sends him to rebuild Lyoko.)
- Sixth Ranger Traitor: William, although not willingly, ends up defeating the Lyoko Warriors one by one.
- Subverted Catchphrase: When Jim tells Ulrich and Odd about how he was a roller derby champion back in the 70's.Ulrich: Oh, what a shame that you would rather not talk about it.
Jim: Actually, I'd be glad to talk about it, but I don't have the time! - The Juggernaut: XANA!William easily defeats the rest of the Lyoko Warriors.
- The Bus Came Back: Two characters who previously appeared once in Season 1 reappear: Ulrich's father, who appeared in Zero Gravity Zone, and Odd's love interest Samantha Knight, who appeared in Rock Bottom.
- Wham Episode: Appropriately for a season finale:
- William officially joins the group, and goes to Lyoko for the first time, making him the first person other than the original five (and Franz Hopper) to be virtualized onto Lyoko.
- Ulrich's father and Odd's love interest Samantha return after both only appeared once in season 1.
- William is possessed by the Scyphozoa, manages to defeat all of the other Lyoko Warriors, and XANA is finally able to destroy Lyoko.
- Wham Line: At the end of the episode, when it looks like the Lyoko Warriors have lost everything: Jérémie reveals that he received a message over the internet, from Franz Hopper.Jérémie: I just received a coded message... a message directly from the Internet, and it's signed-
Aelita: Who? Tell us Jérémie!
Jérémie: "Franz Hopper".
