The episode opens in the school cafeteria, where Kadic students are excited to learn that Chris Morales, the drummer for the Subdigitals, is coming to campus to visit Jim, his uncle. During an assembly, it is revealed that Chris is also at the school to hold auditions for aspiring young DJs who wish to open for the Subdigitals at their next concert.
A large crowd of students, including Sissi and Odd, arrive at the gym for auditions. Aelita, who enjoys making music, also plans to try out, but is talked into helping Jeremie work on a program for a "virtual ship" instead. Odd, like most other students, does poorly during his audition, leaving him disappointed, and also leaving Chris frustrated over an apparent lack of talent among the students.
While working, Jeremie notices Aelita is distracted and allows her to leave so she can audition. However, when she arrives at the gym, no one is there, and she plays her demo once in the empty gym before leaving. Unbeknownst to her, Chris is right outside the gym on break and hears her song. Aelita's track is immediately his favorite, but when he reenters the gym to discover the DJ's identity, Aelita is already gone. It is then revealed that X.A.N.A. has activated a tower in the Forest Sector. While Chris is alone in the gym, a spectre emerges from the turntable on stage.
When Aelita learns Chris is looking for the "Cinderella" DJ, she rushes to find him. The presumably possessed Chris then knocks Aelita out and takes her to the Factory. Meanwhile, in his dorm, Jeremie is alerted to the activated tower by the Superscan and calls the others to meet in the courtyard. When Aelita does not show, Odd and Ulrich go to look for her on campus while Jeremie and Yumi head over to the Factory.
On their way off campus, Yumi and Jeremie learn of Aelita's kidnapping from Milly and Tamiya, who saw it happen, and Jeremie calls Ulrich to inform him of Chris' possession. However, Ulrich and Odd find Chris talking with Jim, and after realizing that the former's pupils don't have X.A.N.A.'s symbol in them, the two boys deduce that the Chris who kidnapped Aelita is actually a polymorphic clone.
In the Factory, the clone places Aelita into a scanner before reverting back into a spectre and manipulating the interface in the lab to virtualize her onto the Forest Sector. Aelita regains consciousness on Lyoko and finds William with two Krabs advancing on her. Jeremie and Yumi arrive shortly afterward, and Yumi is sent to Lyoko to protect Aelita. Meanwhile, Ulrich and Odd make their way to the Factory, but are stopped by Jim and Chris, who demand to know where they are going. Having no choice in the matter, Ulrich agrees to take them with Odd to the Factory.
On Lyoko, Yumi faces off with William and Aelita runs off while pursued by Krabs. In the lab, the Polymorphic Clone reappears and attacks Jeremie. When Odd, Ulrich, Jim, and the real Chris arrive in the lab, Chris and Jim begin fighting the clone while Jeremie sends Odd and Ulrich to Lyoko.
Meanwhile, Aelita attempts to escape the Krabs using her wings, but is shot down, and has to be saved from the Digital Sea by Jeremie, who programs her an Overwing. Yumi and William continue to battle as Odd and Ulrich arrive. Odd engages the Krabs while Ulrich goes to help Yumi.
Ulrich arrives just after Yumi is devirtualized by William, and takes her place battling him. William then summons his Black Manta to attempt to overwhelm Ulrich, but Odd arrives, having defeated the Krabs, and begins to help out Ulrich. Aelita then reaches the tower and deactivates it. Defeated, William returns to the Digital Sea.
In the lab, the polymorphic clone disappears, and Jim demands an explanation from Jeremie. However, Jeremie performs a return to the past to erase Jim, Chris, Milly, and Tamyia's memories.
Back at campus, just before the auditions, Chris arrives at Jeremie's dorm as he and Aelita start work on the virtual ship. Chris has somehow already gotten hold of Aelita's demo track and wants to talk to her about opening for the Subdigitals. When she asks where he got it, Chris tells her it was given to him by one of her friends. The "friend" is implied to be Jeremie as he smiles after them.
- The original French name for this episode is Première partie.
- In this episode, it is revealed that the Subsonics' name has been changed to the Subdigitals by the record company.
- Early in the episode, Jeremie refers to the program he and Aelita are working on as a "virtual ship". This is the first reference to the Skidbladnir.
- This is the only episode where William is shown using his Second View ability.
- This is also the only episode to feature a Manta appearing in the Forest Sector.
- At the start of the episode, Yumi expresses confusion over who the Subdigitals are, despite claiming to be a big fan of them in Season 2.
- When X.A.N.A. Chris returns, he is no longer wearing sunglasses.
- When Yumi, Ulrich, and Odd are in the scanners, they appear to be wearing their new season four outfits even though these attires are not supposed to be revealed until Maiden Voyage.
- When Yumi is being virtualized, Jeremie says "Scanner, Yumi" before "Transfer, Yumi". This is incorrect.
- It is also worth noting that Jeremie made the same mistake when he was virtualizing Aelita in A Bad Turn.
- In some shots in the lab, the Holomap shows that Sector Five is the only sector on Lyoko that has been recreated even though Jeremie restored all of the other four sectors by this point.