Code Lyoko Wiki
Code Lyoko Wiki

Virus is the eighth episode of Code Lyoko Evolution and the overall one hundred and third episode of Code Lyoko.


The Lyoko Warriors decide to go on the offensive; Jeremie tests a virus with Aelita. While the brainiac is at the controls on Earth, Aelita tests it in person on Lyoko. She and Jeremie develop a virus capable of penetrating the Core of the Cortex and destroying it, along with X.A.N.A.'s access to the network, and its ability to launch attacks.

Jeremie and Aelita test a blank version of the virus on Lyoko, incapable of damage. The Supercomputer generating the Cortex was based on Lyoko's model, so it is logical that if the virus works on Lyoko, it will work on the Cortex. Unfortunately, the blank version of the virus fails. It reaches the Core and is destroyed.

Jeremie runs into a block. He makes a proposition that not everyone likes: ask for Laura's help, the new student in their class who has already proven her advanced knowledge in computing. Jeremie proposes using her to finish the virus and then launching a return to the past to erase her memory and get her off their backs. The heroes are reluctant, because using Laura like that is not very moral; however, they end up backing Jeremie up because he says he has no way of finishing the virus alone.

The Warriors go to find Laura in the library. Odd steals her tablet to get her to follow them to the factory, which she does. Trapped in the lift, she winds up in Jeremie's lab, flabbergasted and impressed. Briefed by Jeremie, she accepts to help them with the virus if they agree to explain everything to her afterwards. Jeremie avoids the subject and leads Laura to the terminal. She sets to work with disconcerting speed. After a day of work, the virus is ready, tested on Lyoko, and functional.

Laura then asks Jeremie if he will use a jump back in time. The heroes are shocked that she figured out their plan by reading lines of code on the Supercomputer relating to the return to the past program. Jeremie launches the command while Laura shoots him an icy stare.

Returning to that afternoon, everything is back to normal and Laura remembers nothing. The heroes leave for the factory immediately to return to the Cortex and infect it with the virus. Only William stays because he has tutoring. He agrees to meet up with them later.

Unfortunately, Laura begins to have flashbacks and wanders around Kadic in search of answers. While the heroes leave in the Skid and traverse the Network towards the Cortex, Laura asks William worrying questions. After she leaves he warns Jeremie. Aelita is devirtualized to help Jeremie find the problem with the return in time program.

While Laura gets closer to the secret passage in the park with William on her heels, Aelita discovers the problem Laura had caused. She inserted some lines of code into the virus to tamper with the return to the past. Being tested directly on the Core of Lyoko, the program had rendered Laura invulnerable to the return trips.

Odd is at the controls of the Megapod. More accustomed to it than Yumi, he crosses the Cortex without trouble. Arriving in front of the Dome, the heroes are confronted by the Cortex' defense system. A platform turns and Odd falls towards the Digital Sea. Jeremie devirtualizes him just in time. The movement opens the core's entrance and Yumi and Ulrich enter the Dome. At the same time, Laura enters the lab with William, who could do nothing to stop her. The atmosphere is icy between her and Aelita. The Lyoko Warriors wanted to take advantage of her skills, and she simply defended herself.

Ulrich and Yumi make it to the terminal and Jeremie sends the virus. A firewall blocks the program and an alarm sounds. At the factory, Jeremie detects numerous foreign presences. In the Cortex, Ulrich and Yumi do not see anything but hear suspicious noises.

A new creature appears: the Ninja. This virtual entity is of humanoid form and holds twin blades, capable of traveling through solid objects. Looming behind Yumi, one of them devirtualizes her. Ulrich tries to confront them. He charges, but is knocked down and devirtualized by a single Ninja. Severe setbacks.

At the lab, the results are difficult to digest: the virus failed to work. With this and the appearance of the Ninjas, Laura finds it evident that the Supercomputer generating the Cortex has undergone alterations. Therefore, the tests on Lyoko cannot affirm the success of any virus on the Cortex.

In their room, the heroes discuss Laura… but the whole thing happened too quickly. With the team now knowing they cannot get rid of her, they then decide to tell her as little as possible and to only include her when she is really needed. The episode ends with Laura entering Jeremie's room with a satisfied look on her face.


  • The Catalan subtitles can be found here: Virus Catalan Subtitles.
  • The Core of Lyoko no longer has shield layers or contains the holomap image of the four sectors.
  • The Ninjas make their first appearance in the core of the Cortex.
  • Laura is once again able to get past the elevator keypad, likely by using the same hacking method seen in Mrs. Einstein.
  • This is not technically the first time the return to the past has failed to completely erase a person's memories; the episode Double Trouble sees William describing a dream which recalls the supposedly-wiped events of The Secret. The reasons for this incident are unknown, however, whereas the explanation for Laura's retained memories is specifically clarified in this episode.
  • It is interesting to note that the Lyoko Warriors give as their reasoning for getting Laura to help them and then making her forget everything with a time reversion: that the ends justifies the means. This attitude was heavily frowned upon in the previous four seasons, especially Ulrich in The Chips Are Down and Odd in Straight to Heart.


  • While Laura may be able to make an addition to the list of brains to be preserved in their present state while everything else is rewinded, the Supercomputer would still need a way to recognize such brains, by scanning their owners at least once, and Laura never was.