At the beginning of the story, Odd is listening to very obnoxious music whilst Ulrich is studying for an exam (the music titled "Glad when You're Bad"). He claims nobody knows who wrote it. After Odd starts urging Ulrich to listen to the music too, Ulrich leaves and goes to Jeremie's dorm, where Jeremie is working on a robot. Odd continues listening to the music but suddenly faints on his bed as Kiwi jumps around, barking.
Ulrich ends up sleeping in Jeremie's room, but constantly wakes up during the night because Jeremie, it appears, talks in his sleep about Aelita, much to his embarassment and Aelita's happiness. In the morning they attend class, and when Odd doesn't show up for his exam, they go and try to found out what happened to him. They find him grinning and yet unconscious and transport him to the Infirmary.
The Nurse finds out Odd's pulse is dangerously low, and transports him to the hospital, and Ulrich and Jeremie go too. Meanwhile, Sissi faints from her music, and Yumi barely makes it to the Factory. Pretty soon the whole school is unconscious, and XANA even attacks the nurse.
Meanwhile, Jeremie converses with Aelita about any activated Towers. He and Ulrich make it over to the Factory and meet Yumi there. Ulrich and Yumi go to Lyoko to assist Aelita in the Mountains. They are attacked by a group of Blocks, That managed to freeze Ulrich. Yumi survives and races with Aelita to the Tower. Ulrich sacrifices himself for the two.
Suddenly, the killer music starts playing in the Factory. Jeremie manages to punch in the "return to the past" button before he faints though. Ulrich, who also died, goes unconscious, but before Paris (and soon the entire world) dies, Aelita deactivates the Tower and everything goes back to the day before the exam. This time, Odd downloads a different tune called "Under My Cover" by R.U. Clegmatic, which he claims is a song "a machine" would have written. Whom Odd is referring to is XANA.
This episode contains examples of:
- Brown Note: The song "Glad When You're Bad", which XANA made and uploaded to the internet to induce a coma into people.
- Glasgow Grin: Xana's music gives Odd and other people infected with his song a rather horrid one.
- Heroic Willpower: Jeremie wills himself to crawl over to the computer and type in commands for the return trip. Once done, he finally gives in to the coma.
- Let's Get Dangerous!: "Who said I would be alone?" Ulrich to Yumi, about ready to slice some Bloks.
- Jerkass Has a Point: In the beginning of the episode Ulrich isn’t to be angry with Odd or call selfish for being obnoxious while listening to music while he was trying to for an exam, especially since he is currently not doing well in his classes at the time.
- Missing Mission Control: Courtesy of XANA playing the song in the lab via pipes, Jeremie is also affected by the song, though he holds on for quite a long time in comparison to other characters by focusing on typing in co-ordinates for the return trip. Amusingly, as soon as he's done so, he just flops on his chair as if it finally took hold.
- My God, What Have I Done?: Ulrich has one when he realizes that Odd is in a coma. He shows regret enough to go into the ambulance and follow Odd to the hospital. Then when he is told to go to Lyoko after what XANA had done, he tells Odd that "We'll [he and Jeremie] get you out of this. I swear we will" in a very vengeful voice.
- No-Sell: Jeremie tries to get away from the "Music = Coma" situation by unplugging the speaker. However, XANA plays it over the pipes, weakening him.
- Once an Episode: Subverted; Jeremie's "Return to the past, now!" catchphrase isn't heard here, a rare occurrence in the series.
- The Power of Rock: XANA's evil scheme involves distributing music with some subliminal infection. And does so over the internet, meaning it has the potential to be his most far-reaching plan to date.
- Talking in Your Sleep: After a falling out with Odd, Ulrich sleeps in Jeremies room. Part of the reason Ulrich doesn't get much sleep in preparation for a test he's taking is because of Jeremie's fantasies:Ulrich: Well, I'll tell you "how come." (not even bothering with Jeremie's voice) Aelita... Oh, Aelita, you're in my dreams. I can't wait until—Jeremie: (covering his mouth with his hand) She'll hear you!
- The very next shot is the "Travelling to a Lyoko Tower with Aelita inside", in which she's shown smiling, implying she heard everything Ulrich said.
- You're Insane!: Yumi calls Ulrich crazy when he wants her and Aelita to go deactivate the tower while he slices some Bloks.
