Jeremie uses the Supercomputer's voice synthesizer to convince Mr. Delmas he is William's father, and tells him William has gone overseas to account for his absence from school. Later that day, the Lyoko Warriors relax in the courtyard, and Jeremie and Aelita reveal they have been using data sent to them by Franz Hopper to recreate Lyoko. That evening, the group travels to the Factory, where they succeed in resurrecting Carthage, with Jeremie promising the other Sectors will follow with time. After they leave the Factory for the night, William somehow returns to Earth in a Scanner.
The next day, when the others find William on campus, he claims he does not remember what happened after Lyoko was destroyed, and that he simply woke up in the Scanner Room the night before. While the others are relieved William is safe, Jeremie is curious about how he escaped Lyoko's destruction. Later that evening, Sissi, looking to start more drama under the guise of reporting for the paper, pesters Aelita in her dorm about her (fabricated) backstory before William arrives and demands she leave. Once he and Aelita are alone, it is revealed that William is still under X.A.N.A.'s control. He knocks Aelita unconscious and brings her to the Factory, where he virtualizes both of them onto Sector Five.
Meanwhile, Jeremie learns about William's visit to Aelita's room from Sissi, and begins to suspect foul play. He notifies Ulrich and Yumi to meet at the Factory, but cannot reach Odd. It is then revealed that Jim, convinced Odd is responsible for the news story on Paco, The King Of Disco, is forcing him to learn the dances performed in the film. Because of this, Ulrich is unable to reach Odd.
On Lyoko, Aelita wakes up and manages to escape from William. Ulrich arrives at the Factory, and Jeremie sends him to Lyoko, where he confronts William. However, William demonstrates his new Super Smoke ability and chases after Aelita, leaving Ulrich to battle several Creepers instead. Yumi then arrives at the Factory, and is sent to Lyoko as well.
Meanwhile, it is revealed that many Kadic students enjoy Paco, The King Of Disco, and arrive at Odd's lesson to show their appreciation for Jim. While Jim is distracted, Odd notices Ulrich's missed calls and slips away to the Factory. In Carthage, Aelita is cornered and recaptured by William as Yumi arrives to help Ulrich. In the Celestial Dome, William and Aelita board a Black Manta, and Jeremie deduces William's plan is to dump Aelita into the Digital Sea.
Yumi and Ulrich arrive at the Celestial Dome and give chase on vehicles as Odd finally reaches the Factory and is sent to Lyoko. The Black Manta releases Mines, and Ulrich is devirtualized in an explosion. William, Aelita, and Yumi then exit Sector Five with Odd in tow, entering a vast expense above the Digital Sea where the other Sectors used to be.
After a short aerial battle, William destroys the Overwing and Yumi falls, forcing Odd to devirtualize her before she hits the Digital Sea. William then attempts to dump Aelita, but Odd manages to catch her before destroying the Black Manta. Odd and Aelita return to Carthage as William, his plan foiled, retreats back into the internet.
Some time later, the Lyoko Warriors discuss William's fate and X.A.N.A.'s new strategy of trying to force Aelita into the Digital Sea. They then attend a concert where Jim recreates scenes from Paco, The King Of Disco.
- The original French name for this episode is Renaissance, which translates to Rebirth in English.
- According to Jeremie, he and Aelita recreated Lyoko using data from the message sent by Franz Hopper in Final Round.
- William's new X.A.N.A.-themed avatar debuts in this episode.
- This is the last episode to feature the characters' original Lyoko avatars. Starting with the next episode, Aelita, Odd, Ulrich, and Yumi receive updated avatars.
- This was the last episode to feature Laurent Turner as writer.