Ulrich returns to his dorm room after a morning shower to find Odd in an excitable mood. The two then discuss Odd's plan to ask out Azra Ürgüp, a girl in their class. However, as Odd readies himself to go to breakfast, he accidentally knocks a hand mirror off a table and breaks it. Ulrich informs Odd of the superstitious notion that breaking a mirror causes seven years of bad luck, but Odd does not believe in superstitions, and on the contrary claims to feel empowered and optimistic. However, as soon as he opens the door to leave the room, Jim appears and gives him eight hours of detention for a prank he did not commit. When Odd tries to defend himself by naming Herb and Nicholas, as the real culprits, Jim gives him four hours of detention, this time for "selling out [his] classmates".
Once in the cafeteria, Odd's bad luck continues as the kitchen is out of his favorite foods. At a table, the other Lyoko Warriors discuss returning to the American military base and destroying its supercomputer, which they plan to do that night. When Azra arrives in the cafeteria, Odd approaches her and asks her on a date under the pretense of learning Turkish, her native language. However, Nicholas and Herb interject and confront Odd about selling them out to Jim. Azra, unimpressed with Odd, calls him a budala before walking away, which Jeremie then reveals that it is the Turkish word for "numbskull" (which is incorrect).
Some time later, the gang sets off to the Factory, where Aelita, Odd, Ulrich, and Yumi are virtualized onto Lyoko, and use the Skid to travel to the Desert Replika. After the group discusses superstitions, Jeremie sends Yumi and Odd to the military base. However, Odd's translation fails for the first time, and Ulrich is then sent in his place. Jeremie then detects an activated tower on the Replika, and Aelita and Odd exit to Skid to deactivate it.
At the military base, X.A.N.A. uses the activated tower to send Kankrelats to Earth, which attack Ulrich and Yumi. After a short battle, the pair escapes into the underground area of the base, where they find the assembly line that Ulrich and Aelita discovered on their last trip. On the Replika, Odd's avatar begins to experience bugs as he and Aelita are confronted by a swarm of Hornets. In the subsequent battle, Odd performs well until his avatar glitches again, after which he loses consciousness and is devirtualized.
In the assembly room, Yumi accesses a control terminal to look for information on what X.A.N.A. is manufacturing. Meanwhile, Aelita is chased through a canyon by the remaining Hornets on her way to the tower. As she approaches the tower, she too is affected by the bug, causing her to crash the Overwing. As Yumi deduces the assembly line is making "motherboards and electronic implants", she and Ulrich are attacked once again by the Kankrelats. Jeremie begins directing them to the supercomputer, which he calls the "super calculator", until he discovers William has arrived on the Replika to attack the defenseless Skid.
Yumi agrees to return to the Replika and intercept William while Ulrich continues on through the base. Meanwhile, Aelita is affected by the bug a second time and is devirtualized before reaching the tower. When Ulrich arrives at the super calculator room, he finds it infested with Kankrelats and retreats. Meanwhile, Yumi duels with William in front of the Skid and defeats him. However, before she can be translated back to the base, she is affected by the bug as well and is devirtualized.
In the lab, Jeremie finally discovers the glitches are being caused by a mandelbug, but does not know how to fix the problem. Meanwhile, on the Replika, two Tarantulas arrive at the Skid's tower and begin attacking the ship. After Jeremie informs Ulrich of his dire situation, he decides to take on the Kankrelats in the super calculator room in a last ditch effort to complete the mission. In an impressive performance, Ulrich manages to defeat all the monsters and destroy the super calculator before the bug devirtualizes him. The mission a success, Jeremie uses a new remote piloting program to fly the Skid out of the vanishing Replika and back to Lyoko.
That night at dinner, Odd trips in the cafeteria and spills his food, after which he finally admits to being jinxed. However, Aelita asserts that luck can change at any time, and when Odd notices Azra has accidentally left her cell phone in the cafeteria, he takes it in the hope that returning it to her will convince her to go on a date. Later, in the dormitory building, Odd receives a text message asking him to meet the phone's owner in the courtyard. However, when Odd arrives, it is revealed the phone belongs to Jim, much to Odd's confusion and disappointment.
- The original French name for this episode is Superstition.
- This episode marks the final appearance of the Hornets.
- This episode also marks the last time in the entire series where Yumi uses her Telekinesis.
- A mandelbug is the name of a real-world software bug that behaves similarly to the one described in the episode.
- It is never stated when or how Jeremie fixed the mandelbug since the problem is never mentioned again after this episode.
- At the beginning of the episode, Jeremie tells Odd that the Turkish word "budala" means "numbskull". However, "budala" is Turkish for the word "fool". The real Turkish word for "numbskull" is "mankafa".
- After Ulrich is sent to the base in Odd's stead, he informs Yumi that Odd is "stuck on Lyoko". However, Odd is stuck on the Desert Replika, not Lyoko.
- When the Replika is disappearing at the end of the episode, the tower Jeremie activated is seen glowing red instead of green.
The original episode summary can be found here.