After Odd starts urging Ulrich to listen to the music too, an irritated 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 Ulrich is stunned at Odd’s condition. Panicked, he and Jeremie take him to the infirmary. The nurse finds out Odd's pulse is dangerously low, and transports him to the hospital urgently, and Ulrich and Jeremie go too. Meanwhile, Sissi falls unconscious by her music.
In the hospital, the doctors find that his blood pressure is dropping rapidly. Ulrich begins to feel guilty. Jeremie contacts Aelita and explains their situation. He’s still not certain X.A.N.A. has anything to do with it: it can’t attack humans directly. But Aelita warns him that there are pulsations in the Mountain Sector; X.A.N.A. has woken up.
At the school, Yumi sees Sissi unconscious; she was listening the same music as Odd: "Glad When You’re Bad" and the sound makes the Japanese girl feel dizzy. She’s certain: X.A.N.A. has created a new song and attacked human beings through their auditory nerves, relaying it to the brain.
Fleeing the music X.A.N.A. is broadcasting on the radio, Yumi joins Jeremie at the factory and explains to him how she discovered the killer music. Ulrich is already on Lyoko in combat with Bloks. One of the four freezes the teen completely with its special eye. Aelita finds herself alone and flees while waiting for Yumi to arrive.
The Japanese girl lands in the middle of the catastrophe in the Mountain Sector and places herself between Aelita and the Bloks. When Ulrich escapes the ice, they defeat the monsters with their combined efforts. On Earth, X.A.N.A. infects all the electrical equipment to broadcast its infected sounds. Millions of people are already lying unconscious everywhere.
In the lab, the music begins to play. Caught off-guard, Jeremie tries to disconnect the cables to stop the killer music, but it does nothing, the music still keeps playing. In a final effort, Jeremie enters the coordinates and parameters for the return to the past, before falling unconscious on the keyboard.
At the hospital, Odd, the first victim, falls further towards cardiac arrest with the goofy smile still on his lips; his electrocardiogram sounds a critical and fatal beep…
The last obstacle on Lyoko, in order to get to the tower, they need to get past a large number of moving rocks. But Aelita, protected by Yumi, manages to get across. She enters the Lyoko code at the moment when Odd’s life begins to slip away. The return in time engulfs a quiet city, an inanimate school, and a hospital where many bodies lie numb.
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 X.A.N.A..
- The original French name for this episode is Musique mortelle.
- The song that X.A.N.A. created is called "Glad When You're Bad".
- This is Matthew Geczy's favorite episode, according to Lyoko: Decoded.
- Killer Music was included in "Movies, Music, and Mayhem".
- In the Finnish dub, the episode's name is Tappavan Hyvää Musiikkia, which literally translates to Killing Good Music.
|Code Lyoko: Season 1|
|X.A.N.A. Awakens | Teddygozilla | Seeing Is Believing | Holiday in the Fog | Log Book | Big Bug | Cruel Dilemma | Image Problem | End of Take | Satellite | The Girl of the Dreams | Plagued | Swarming Attack | Just in Time | The Trap | Laughing Fit | Claustrophobia | Amnesia | Killer Music | Frontier | The Robots | Zero Gravity Zone | Routine | Rock Bottom? | Ghost Channel | Code: Earth | False Start|
|Season 1 · Season 2 · Season 3 · Season 4 · Code Lyoko Evolution|