When Sissi finds and steals Ulrich's diary, he is blackmailed into being her boyfriend. During a trip to a swimming pool, Jeremie and Yumi have the opportunity to find it. The new electric bus that is being used for the field trip is possessed by XANA, with Odd and Ulrich on board, and starts acting bizarre as a result.
Yumi ends up finding Sissi's diary during this, and uses it to blackmail her into giving up the location of Ulrich's. XANA then turns the bus on Paris's petrol-chemical plant, threatening to blow up a sizable portion of the city. Yumi is sent to Lyoko to help Aelita but she is devirtualized in the process but luckily Odd manages to escape from the bus, leaving him to take Aelita safely to the tower to deactivate it, saving the bus full of students and the petrol-chemical plant.
This episode contains examples of:
- Artistic License – Physics: Odd should have been paralyzed from his jump off the bus onto concrete (or even worse), but he manages to get up and walk away with only a minor shoulder injury.
- Bait-and-Switch: Yumi thinks she has Ulrich's diary at last...only to find out it's Sissi's.
- Blackmail: Ulrich was blackmailed when Sissi threatens to put his diary in the paper. He wrote about Lyoko, as well. This is a part of the B plot.
- Brief Accent Imitation: Yumi makes a high-pitched impression of Sissi, reading off one of her diary entries over the phone to her.
- Early-Installment Weirdness: The team is surprisingly nonchalant about the fact that Ulrich writes in his diary about Lyoko, considering how angry they would be in later seasons if someone accidentally leaked Lyoko.
- Homage: XANA's hijacking of the new bus which it sends it on a collision course with a chemical plant, is eerily similar to the plot of the hit 90's film Speed, though unlike the mad bomber (whose bus was destroyed), XANA's bus stops just seconds before it could collide with the plant, but much like the film, no one is killed.
- Haunted Technology: XANA takes control of the bus in an attempt to ram it into a chemical plant and dispose of Odd and Ulrich in the process. However, Odd gets away to help Aelita on Lyoko.
- Out-Gambitted: Yumi recovers Ulrich's journal by finding Sissi's diary and threatening her with it.
- There's No Kill like Overkill: For the second time this season, X.A.N.A's plot is to ram an electric bus into a Petrol-Chemical plant, which much like the nuclear reactor plot from two episodes ago, would have destroyed most of Paris, France (though the blast radius would have been far smaller compared to the nuclear meltdown scenario from the previous episode), though it still would have killed a bunch of people aside from Ulrich.
- You're Insane!: Aelita calls Odd "out of [his] mind" when she finds they are running toward an edge in the middle of a tornado with a MegaTank in it.
