In Lyoko's Ice Sector, two Hornets circle around an activated tower. Meanwhile, Odd, Ulrich, and Jeremie are in Mrs. Hertz's class, listening to her lecture on neutrons. She asks the class what happens when two neutrons collide and Herb raises his hand.
Suddenly, everyone's cell phone rings simultaneously. The students answer the call, only to find out no one is on the line. Sternly, Mrs. Hertz orders Sissi, the principal's daughter, to recite school policy on cell phones. Speaking in a monotonous voice, she says: "All mobile phones have got to be turned off before entering the classroom, under penalty of having them confiscated". Immediately, Mrs. Hertz orders the students to turn in their cell phones, just as the bell rings. Reluctantly, the students put their phones on her desk and walk out.
In the hallway, Yumi runs up to Odd, Ulrich, and Jeremie, telling them that all the cell phones went off in her class. Suspicious, Jeremie leaves to check if XANA is involved. Ulrich notes that without their cell phones, XANA will have a major advantage.
Sissi and her gang walk up to them. Sissi tells them that she's organizing a meeting, regarding the cell phone confiscations and asks if they're with her. Much to Sissi's surprise, Yumi agrees to it. Sissi then tells her to go to the Auditorium after lunch.
In the Factory, Jeremie establishes a connection with Aelita, who is sitting within a tower. He asks her if she's detected anything strange on Lyoko. Aelita tells him no, but says she will feel around for pulsations. After terminating the link, Jeremie starts scanning each tower to check for XANA.
In the Cafeteria, Odd quietly converses with Yumi about taking back their phones discreetly. Yumi dismisses it as stealing. On the other side of the Cafeteria, Principal Delmas, Mrs. Hertz, and Jim are also having lunch. Mr. Delmas tells Jim and Mrs. Hertz that he won't be returning the phones anytime soon, saying they were warned before. He tells Jim to disable the School Antenna, which would cut off cell phone service on campus.
Back at Odd, Yumi, and Ulrich's table, they are still debating whether or not to take back their cell phones. Ulrich tells them that they have no choice, considering what would happen should XANA attack and they can't be in contact. Yumi turns around to look at the administrative staff, and when she turns back, Ulrich and Odd are gone.
In the Administrative Building, Odd and Ulrich sneak into the teacher's lounge. Ulrich keeps watch in the hall, while Odd tries to pick the lock on Mrs. Hertz's locker. With a click, the lock is broken and Odd sees the cell phones inside. Unfortunately, he suddenly hears Ulrich say hi to Gilles Fumet, a teacher. Immediately, Odd ducks under the table in the middle of the room as the teacher walks in. He sees the man's legs walk up to the table. A pen rolls off the table and onto the floor, definitely a bad thing if the man looks down there. Luckily for Odd, Fumet feels around with his feet and slides the pen out, picking it up without looking. The teacher then leaves the room, allowing Odd to get up and gather a few cell phones.
In Jeremie's room, Yumi and Jeremie are still watching the screen, looking for activated towers. Odd comes in and drops three cell phones on the bed. They take their phones, but on them is the Eye of XANA.
Yumi leaves to go to Sissi's meeting as the three boys go to the School Antenna to check for network problems. They come up to the roof to see Jim about to disconnect the antenna. Suddenly, he is electrocuted and falls, but Odd and Ulrich grab him and drag his unconscious body back up. Odd and Ulrich take Jim to the Infirmary, but Jeremie stays behind with an EM detector to look for problems.
Yolanda Perraudin walks into her Infirmary and is shocked to see Jim lying on a bed. Odd, who is standing next to him, tells the nurse that Jim's a live wire.
On a rooftop, Jeremie finds a stronger electromagnetic field in the direction of the dish atop the nearby TV station tower. In the Auditorium, people are signing Sissi's petition as Yumi walks in. As she is about to sign it, Principal Delmas and Mrs. Hertz walk in, demanding to know what's going on. Sissi confronts her father, showing him the petition. Mr. Delmas responds, saying that students don't make the rules, and that Mrs. Hertz's locker was opened by someone to take several phones. Jeremie appears in the window, telling Yumi to meet him outside. Yumi runs out of the building as Sissi rallies her protesters in a walk-out of school.
In Jeremie's room, Jeremie explains to his friends that XANA used the School Antenna to plug into the television dish on top of the PAJH television building. In doing so, XANA jammed the frequencies and set off everyone's phone. He adds that from the TV dish, XANA can take control of a military satellite.
Jeremie finds an activated tower, as Aelita pops up on the screen and reports an activated tower in the Ice Barrier sector. They leave to go to the Factory, but Kiwi manages to escape and follow them, undetected. Outside, Sissi is preparing her followers, wielding signs, for a protest. She comes up with the line: "No more phones? No more school!".
Jeremie and the others come outside, where Yumi tells them she will stay to look out for a XANA attack. The boys then leave without her. Seeing Yumi ditching her responsibilities to the effort, Sissi tells her to join the ranks. With a toothy grin, Yumi walks over.
The boys arrive at the manhole cover in the Park, but they find Kiwi following them. Jeremie comments: "Incredible. For a dog, he's as stubborn as a mule." They then climb down into the Sewer, with Kiwi.
Jeremie starts up the computer interface in the Lab as Odd and Ulrich enter the Scanners. Jeremie then virtualizes them into the Ice Barrier sector, near Aelita, whilst he starts looking for military satellites XANA may hack into.
Meanwhile, Sissi's protesters are having a sit-out in front of the Administrative Building, shouting: "No more phones? No more school!".
Jeremie hacks into a military database and finds an entry for a satellite, called U4-66, which is armed with a destructive laser beam. Jeremie knows that XANA wouldn't fire on the Factory, because he would be destroying himself. However, Yumi isn't there and can be the laser's target. Unfortunately, her phone was confiscated and they can't contact her. Jeremie then realizes that he can send Kiwi as a messenger.
Principal Delmas comes out of his office and demands the protesters stop their strike. Kiwi comes up to Yumi, with a note attached to its collar. Seeing this, Principal Delmas drags Yumi and Kiwi back into his office. Immediately, she becomes a martyr to the others, who chant: "Free Yumi!".
On Lyoko, the three are informed the activated tower is across a narrow bridge. Unfortunately, it is guarded by several Hornets. Jeremie warns them of the Hornet's poison, which will kill off their life points. Odd wonders why the Hornets aren't firing. Jeremie replies, saying the Hornets are to keep them there until XANA takes control of the satellite. Odd then fires the first shot, but misses. A Hornet squirts poison, but misses, just inches from Aelita.
In his office, Principal Delmas is yelling at Yumi. Yumi, takes the note from Kiwi's collar, reads it, and runs out, telling him that everyone has to evacuate. Mr. Delmas just lies down in his chair and sighs. On Lyoko, ponds of poison seperate the Team Lyoko from the Hornets. Odd decides to distract the Hornets while Ulrich and Aelita run towards the tower. He runs past the Hornets, who follow him. He loses 70 life points to the lasers and poison as Aelita and Ulrich run across the narrow ice bridge.
In the Lab, Jeremie finds out that XANA has just taken over the military satellite. Yumi runs out of the Administrative Building, where Sissi asks why she got out. Making up an excuse to get everyone off campus, Yumi tells her that they have to bolster their movement and recruit people off-campus. This surprises Sissi, who had apparently never thought to take her protest so far. Agreeing, she rallies the others and they begin to march towards the school gates.
Jeremie watches live telemetry on his computer screen of the laser's targeting lock. The screen shows the targeting crosshairs zooming into France, then a suburb of Paris, then to the city block Kadic is on.
As the protesters approach the gates, Principal Delmas shows up and blocks them, forbidding them to leave the grounds.
On Lyoko, Ulrich and Aelita reach the specified location, but there is no activated tower in sight. Odd is devirtualized by laser fire from the Hornets, which then fly off towards the other two. Ulrich and Aelita jump off a plateau, onto a ledge. Here, the Hornets catch up and start firing. While Aelita makes her way down, Ulrich uses Triplicate and fights the Hornets.
In the Lab, Jeremie sees the targeting crosshairs lock onto a person's head. Infrared imaging confirms it's Yumi. Odd comes up to the Lab, when Jeremie warns him that the satellite laser is locked onto Yumi.
At the school gates, Yumi pleads with the principal to let everyone off-campus. Principal Delmas then suspends Yumi for a month and tells her and her dog to get off campus immediately. He then orders the other students back to their classrooms, effectively quashing the protest "Bring Back Mobiles!". Odd runs out of the Park, shouting that the satellite is after her. She then runs off to catch up with him.
On Lyoko, Ulrich stabs a Hornet, but he's still losing the fight. One of his clones is hit and disappears, while the real one is hit and falls from the ledge. Aelita dodges laser fire, noticing a waterfall near her.
Meanwhile, Odd and Yumi dive out of the way as a laser bolt streaks down from space and blows up the ground. In its wake is a massive crater. Seeing the smoldering crater in the distance, Principal Delmas orders the evacuation of the school.
Aelita decides to look behind the waterfall, finding the tower surrounded by water.
Meanwhile, Odd and Yumi are hiding under some trees. To get to the Boiler Room and to the Factory, they have to run across the track. They run, but the laser has already been fired. Aelita deactivates the tower, stopping the laser bolt, just inches from Yumi's head. Jeremie then activates a time reversion, sending everyone back to the beginning of the day.
Odd, Ulrich, and Yumi put signs on the windows of the Cafeteria. Sissi comes out and reads the poster: "Official School Policy Reminder To All Students: All moblie phones not turned off before entering the classroom will be immediately confiscated." She dismisses them as teacher's pets and walks away.
- The original French name for this episode is the same as the English.
- This episode shows the location of the show, France.
- This is the second time Kiwi was caught.