Jeremie has created a EMP bomb, which can destroy a person possessed by XANA/ Release XANA's control of that person. At Kadic Academy, Sissi comes up to Ulrich, Aelita, and Jeremie, telling him Yumi is with William. Jeremie picks up an activated tower, and tries to leave for the Factory with the others, however, Jim stops them before they can go, telling them to go to class. Principal Delmas goes in the direction of Yumi, Odd, and William. Odd says he has to get to music class with the others, while William states that he's lucky, as he has chemistry. The principal, possessed by Xana, approaches and grabs Yumi and Odd. William objects to this behavior, and tries to stop him, but he throws William into the school. Delmas drags Yumi and Odd to his car, putting them there and closing the doors. Yumi can only call out to William as she and Odd are driven away.
Later, while Nicholas is playing a car racing videogame, he hears from William that the principal has "gone crazy", and tells other people the details about it. In music class, the teacher is playing an instrument, but no one seems to care much. Nicholas then enters the room, telling the teacher about Yumi and Odd's predicament, which Jeremie realizes has to do with XANA. The teacher then goes to see what it is about. XANA text messages Jeremie. The message reads "Aelita at 2 'o clock in the Ice Sector to give herself up to the Scyphozoa. If not, Odd and Yumi will be liquidated." They stand up and try to go, but the music teacher opens the door and orders that everyone sit down immediately. At a warehouse, Yumi and Odd wake up, and he comments that given the temperature, they must be in Siberia. Odd then tries to walk up to the principal, but he gives him a shock, sending Odd back. Back at Kadic, Jim announces that classes are cancelled for the day as the rest of the group try to sneak out. Sissi points out they might be involved, so the police officers try to grab them, forcing the Lyoko Warriors yo run for it, however, only Ulrich makes it into the forest where the sewer cap is located. He gets a skateboard from the wall and grinds a rail as Odd explains to the principal that cold can kill them too. Delmas throws them his jacket to prevent them from freezing to death before the right time.
Meanwhile, Aelita and Jeremie are outside the principal's office, where they discuss with Sissi the entire details of what's happening to pricipal Delmas, while Yumi's cellphone drops from Delmas's jacket. By then, Ulrich is almost at the Factory when Yumi calls him and manages to tell him their rough location before Delmas sees her and destroys their phones. Ulrich then sees the EMP bomb, as Sissi, Jeremie, and Aelita have told Sissi about Lyoko, in hopes of getting her help. By that time, Sissi is called to the office.
Ulrich then sulks a bit because Jeremie hadn't made an instruction manual for the EMP bomb, and pulls switches and presses buttons until the bomb is turned on. At that time, Sissi talks to the officer in charge, and implies his father wanted to detonate a bomb in the school, getting the police to evacuate it. Aelita, Jeremie, and Sissi then run to the factory as Ulrich calls them and Jeremie says there are only 15 minutes left until the ultimatum. At the Factory in the control room, Sissi makes a comment about that she feels like she is in a James Bond movie. They locate the Scyphozoa. Ulrich tries doors at the refrigerator warehouse as the ultimatum is up.
Ulrich then finds them and uses the EMP bomb after Jeremie tells him that the bomb can also simply deactivate anything electronic, breaking XANA's control of Delmas for a bit of time. At the Factory, Sissi knocks out Jeremie in order to virtualize Aelita. She is then chased, as the others are running to the Factory. Aelita then slides down in order to escape from XANA's monsters. One is completely devirtualized from damage as Aelita lands in front of a rock and walks back into the Scyphozoa.
Back in the Factory, Sissi wakes Jeremie up, asking about the Scyphozoa, describing it as a "giant squid" as Yumi and Odd are virtualized. They manage to cut the Scyphozoa's tentacles in time. Odd then shoots laser arrows at it, while outside Ulrich is taking a beating courtesy of the principal. As they go up an ice mountain, Tarantulas materialize, which manage to devirtualize Odd and Yumi. As the principal attacks Sissi and Ulrich, Aelita enters into the tower and deactivates. Afterwards, Ulrich reassures Sissi that her father will be alright, and that everyone will forget about the incident, so Sissi takes the opportunity to kiss him. The Return to the Past then takes place.
Time is reversed to before Sissi insulted them, and after she leaves, Jeremie says "You're still thinking about what happened on the bridge?" Yumi then says "What happened on the BRIDGE?" Aelita also asks the same question. Ulrich says "Nothing". Yumi objects a bit, but Odd says "But nothing really DID happen on the bridge." as Ulrich meets up with Sissi as the bell rings. Aelita tries to tell Yumi "It's just boy stuff" to Yumi, who remains unconvinced.
This episode contains examples of:
- Action Girl: Sissi fends off her father being possessed by XANA for at least a moment.
- Big Word Shout: The beginning of the episode has Odd and Yumi crying for help and William yelling for the possessed principal to stop.
- Blatant Lies:
- Sissi's story of how her father wants to blow up the school helps Aelita and Jeremie get out of the principal's office.
- Yumi isn't convinced that nothing happened on the bridge specifically because Odd and Ulrich refuse to elaborate.
- Hostage for MacGuffin: XANA, to his credit, tries being uncharacteristically reasonable for once, and kidnaps Odd and Yumi and keeps them hostage. In exchange, they are to give him Aelita so he can get what he wants from her.
- Oh, Crap!: Aelita helps Jeremie realize that cell phones are electronic and that his EMP bomb ended up shorting out Ulrich's cell phone.
- No-Sell: Even an EMP can only knock out a XANA-possessed person for about a minute.
- Sesquipedalian Loquaciousness: Jeremie as per usual. This time he uses Techno Babble to explain how an EMP works, much to the annoyance of Odd.
- Say My Name: William and Yumi do this to each other when she and Odd are kidnapped.
- Shock and Awe: XANA-possessed Delmas electrifies Yumi and Odd until Ulrich stops him with Jeremie's EMP. Delmas does it again later against Ulrich and Sissi.
- Took a Level in Badass: Sissi has this happen to her. She's able to fend off her possessed father as he attacks Ulrich.
- Watch Out for That Tree!: In hot pursuit of Ulrich, after Jeremie and Aelita are apprehended, Jim ends up ramming into a tree, collapsing on his back a few seconds later.
