Jeremie has an idea: since X.A.N.A. sends spectres to collect Source Codes from inside the Lyoko Warriors, Jeremie plans to dupe X.A.N.A. by injecting one of his friends with false codes which, instead of giving X.A.N.A. strength, weakens it. Only one problem: the procedure is experimental and therefore dangerous. After a small debate about who’s going to get the codes, Ulrich volunteers so that Yumi won’t have to. She is touched by his gesture.
She and Ulrich virtualize on Lyoko. They stop in front of a tower. Ulrich enters and is injected with the fake codes. After a small, strange reaction from the tower and computer terminal, Ulrich springs out of the tower and plays a little joke on Yumi, pretending to be possessed by X.A.N.A.. After devirtualization, the Lyoko Warriors return to Kadic, finally ready to welcome their first spectre.
This part of the plan goes well: a tower is activated. The spectre walks around Kadic. It runs into Sissi, who begins to complain, until the spectre hypnotizes her to remain silent. Sissi then begins to wander around the grounds looking sleepy. Ulrich and Yumi, warned about the spectre by Jeremie, begin to search for it. Seeing Sissi desensitized, Ulrich believes her to be the spectre and approaches her. He realizes his mistake when he discovers Yumi being hypnotized by the spectre. He saves her. Yumi flees, but the spectre doesn't attack Ulrich. It hypnotizes him and sets off after Yumi.
Ulrich calls Jeremie. Jeremie realizes his mistake: X.A.N.A. was spying on them when they injected Ulrich with the codes, so X.A.N.A. knows about the trap.
William and Aelita, who were at the factory, go to Lyoko first. During this time, Odd tries to reconcile with Samantha. After a short time hiding from some monsters, Aelita and William are forced to make a confrontation. Aelita, cornered by three Bloks, eliminates one but is devirtualized by a second. William fights against Bloks and Krabs combined. He performs some great feats and destroys most of them.
He’s then joined by Odd who had to give Samantha a new excuse so he could come to the factory. X.A.N.A.’s guard is ferocious. After a brief exchange about their respective hopeless love lives, William charges and is devirtualized. Odd is the only one who can enter the tower, which is well-guarded. After some great manoeuvers on the Overboard, Odd manages to break past the wall of monsters and enter the tower. But he doesn’t deactivate it because…
On Earth, Yumi finds it difficult to escape the spectre while Ulrich can’t seem to find them. The little game of hide and seek finishes in the gym. Yumi is hypnotized but Ulrich manages to seize the spectre. It absorbs his fake codes and disintegrates.
The fake codes mission is a success but Jeremie decides not to try it again because it's too much for his friends, especially since X.A.N.A. became wary of the tactic. The day is concluded on a positive note while Odd tries once again to patch things up with Samantha.
- The original French name for this episode is Comment tromper XANA.
- This is the only appearance of the fake codes.
- This episode contains numerous references to the episode Nobody in Particular, in that it sees Ulrich once again volunteering to be Jeremie's 'guinea pig.' He also jokes about his body being possessed by X.A.N.A., something that actually happened in the aforementioned episode.
- Sissi makes her first appearance in the fifth season in this episode. It seems that she hasn't been as much of a pain as Odd has made her out to be when he first mentions her in this episode.
- She now has blonde hair, rather than black hair.
- It is revealed that William hasn't given up in liking Yumi, despite her relationship with Ulrich so far. It is also revealed that Odd finds William's infatuation with her to be hopeless at this point in time.
- After absorbing Ulrich's fake codes, not only does the Spectre disappear but the tower itself deactivates without Odd's input. This implies that X.A.N.A. lost so much power that he was unable to maintain control of the tower.
- While approaching the tower, William seems surprised that X.A.N.A. has been 'expecting' the Lyoko Warriors. This implies he has still not been briefed on the usual way the Lyoko missions play out, since X.A.N.A. always knows that its activated towers are the Lyoko Warriors' primary targets.
|Code Lyoko Evolution|
|X.A.N.A. 2.0 | Cortex | Spectromania | Mrs. Einstein | Rivalry | Suspicions | Countdown | Virus | How to Fool X.A.N.A. | The Warrior Awakens | Rendezvous | Chaos at Kadic | Friday the 13th | Intrusion | The Codeless | Confusion | An Assured Professional Future | Obstinacy | The Trap | Espionage | False Pretenses | Mutiny | Jeremy's Blues | Temporal Paradox | Massacre | Ultimate Mission|
|Season 1 · Season 2 · Season 3 · Season 4 · Evolution|