X.A.N.A. is wearing the heroes down, causing problems for Yumi when the principal says he will expel her if she's absent again. Jeremie stays up late to find a way to virtualize the four Lyoko warriors into Carthage. But things take a turn for the worst when X.A.N.A. sends a specter with Jeremie's likeness and has it to eliminate Jeremie once and for all. It takes his place at Kadic, but Odd is warned by the real Jeremie about the deception.
Yumi, Aelita and Odd are later virtualized by the genius they think is Jeremie, but ends up bugging up Yumi and Odd, so that the Scypozoa will possess Aelita and have her wipe out the fourth and last region; thus preventing the warriors from stopping X.A.N.A.
While being handed back papers in Mr. Fumet's class, Jeremie does not do as well as usual, and Ulrich receives the worst grade in the class. Meanwhile, in the principle's office, Yumi is reprimanded for frequently being tardy and absent from class, and is threatened with expulsion if she truants again.
That night, the Lyoko Warriors convene at the Factory, where they discuss the toll fighting X.A.N.A. is putting on their personal lives. Aelita suggests recruiting another person into the group and proposes asking William, but Yumi still refuses to trust him. Jeremie advises they talk in the morning, and the others leave the Factory. Jeremie, however, stays up late working in the Lab and falls asleep at the keyboard. The Superscan signals that a tower has been activated, but Jeremie sleeps through the alert, and only wakes up in time to be attacked by a spectre.
The next morning, Jeremie returns to campus and announces that he has found a way to virtualize Aelita, Ulrich, Odd, and Yumi onto Carthage, and tries in vein to get them to truant and come to the Factory. Unbeknownst to everyone, the Jeremie at school is a Polymorphic Clone, and the real Jeremie was thrown into the Seine River. Meanwhile, the real Jeremie manages to swim to safety and returns to the Factory.
In Ms. Hertz's class, Odd is caught cheating on an exam, and Jeremie is asked to escort him to the principle's office. While in the hallway, Odd gets a call from the real Jeremie telling him about the clone. The clone subsequently attacks Odd and knocks him unconscious. Meanwhile, Yumi is in a photography class, where she and William are sent into the darkroom alone. While she is in the darkroom, Jeremie calls her and explains the situation before asking her to gather Odd, Ulrich, and Aelita. William, wanting to impress Yumi, promises to cover for her and allows her to escape out a window.
Yumi finds Odd in the hall and revives him before calling Aelita, who is still in Ms. Hertz's class taking the exam. After Ulrich refuses to go with her, opting to stay to try and get a decent grade, Aelita joins Yumi and Odd, and the three of them travel to the Factory together. Meanwhile, the clone returns to the Factory and attacks the real Jeremie. In the resulting struggle, the real Jeremie is thrown down the elevator shaft, and the clone assumes his place at the interface.
Aelita, Odd, and Yumi arrive at the Factory, and the clone convinces them it is the real Jeremie. However, once they are sent to Lyoko, the clone reveals itself to them and begins tampering with Yumi and Odd's avatars. The Scyphozoa and four Kankrelats then appear, and Yumi and Odd discover the clone has made them entirely intangible. With Odd and Yumi unable to stop it, the Scyphozoa captures Aelita and possesses her. Meanwhile, Ulrich finishes his test and travels to the Factory.
The real Jeremie is revealed to have survived his fall, and uses an emergency ladder to climb back into the Lab. Ulrich arrives in the Lab a short time later and begins fighting the clone while the real Jeremie debugs Odd and Yumi's avatars. Once they are tangible again, Odd and Yumi chase after Aelita, who is heading for a way tower to destroy the Mountain Sector.
Ulrich begins losing the fight against the clone. On Lyoko, Odd stops to confront the four Kankrelats while Yumi continues to pursue Aelita, and he manages to defeat one before being devirtualized. Yumi fails to prevent Aelita from entering the the way tower, and once inside, Aelita inputs the X.A.N.A. Code. The Mountain Sector vanishes, and Jeremie manually devirtualizes Yumi and Aelita before they fall into the Digital Sea. The activated tower vanishes as well, causing the Jeremie clone to disappear.
The Lyoko Warriors reconvene in the Lab, and Jeremie announces he really has found a way to send them all the Sector Five. Yumi finally admits the group needs another member, and agrees to ask William. Later that day, she explains Lyoko, X.A.N.A., and the Supercomputer to him, and he agrees to join.
- The original French name for this episode is Surmenage, which translates to Overwork in English.
- This episode and the one preceding it, Triple Trouble, are very similarly named in the English version of the series. It is unknown whether or not this was intentional.
- Near the beginning of the episode, William confesses to Yumi that he is having recurring dreams related to the events five episodes prior, making this the only known instance where the Time Reversion program is not entirely effective for unknown reasons.
- While Yumi and Odd's avatars are bugged, Yumi is hit with a laser from a Kankrelat, despite it having just been established that she and Odd were intangible and immune to laser fire.
- While taking his exam, Odd is initially shown holding a pen. However, in the next shot, he is shown holding a pencil.
|Code Lyoko: Season 3|
| Straight to Heart | Lyoko Minus One | Tidal Wave | False Lead | Aelita | The Pretender | The Secret | Temporary Insanity | Sabotage | Nobody in Particular|
Triple Trouble | Double Trouble | Final Round
|Season 1 · Season 2 · Season 3 · Season 4 · Code Lyoko Evolution|