It's time for class physicals at Kadic Academy. The various students in the building are discussing their various problems, such as Herb's acne, Juilen's near-sightedness, or Odd's scrawniness. Julien is trying to memorize the eye chart to avoid getting glasses. Odd still refers to himself as svelte. Sissi talks to Ulrich about how her medical record is perfect. Jeremie is talking to Aelita about her lack of any medical record or vaccinations. He's worried that they'll learn she isn't completely human. She's sure everything will be fine, saying that Jeremie seems to find her human enough. The nurse calls in Jeremie, Julien and Odd to start.
In the nurse’s office, Yolanda does little more than confirm what each already knew. Odd is indeed scrawny and Julien is not only near-sighted, but has a bad memory on top of it. Aelita and Sissi are next. Sissi finds out that she's five pounds overweight, not that she'll accept it as true. Aelita asks about her missing medical record, which Yolanda assures her won't be a problem. Meanwhile, Jeremie's computer picks up an activated tower. He has Ulrich wait for Aelita while he and Odd head to the factory. Yolanda is XANA's target and is possessed by XANA's ghost. A scream from Sissi alerts Ulrich to this, but Yolanda has already left with Aelita.
At the factory, Jeremie is informed of Yolanda's possession. He locks down the elevator to slow her down. Seeing as how they can't deactivate the tower, he has a new idea to try out. He's going to make his own ghost to possess one of his friends. That way, they can fight on the same terms.
On the factory floor, Yolanda arrives with Aelita. She finds the elevator disabled and heads for the access corridor. Ulrich shows up to delay her. XANA's victims always get stronger with each possession, and today is no exception. Yolanda has the ability to form energy into concentrated spheres to attack her enemies with. Ulrich isn't much of a match for the attacks.
Back in the lab, Jeremie starts his test by activating a tower in the mountain region. His activated tower is green instead of red like XANA's. He uses his own ghost to possess Odd. Unlike XANA's victims, Odd is in complete control.
Back on the factory floor, Aelita has managed to get away from Yolanda. She's trapped at the entrance to the corridor. Yolanda eventually knocks out Ulrich and heads back to get Aelita. As she does, Odd comes out from the corridor and attacks her. Both are evenly matched. Odd plays for time while Aelita and Ulrich escape.
In the depths of the factory, Yolanda and Odd fight to see who is better. Odd seems to do better at first, using the abilities he just got as if he'd always had them. Yolanda is eventually sent into the water by a blast from Odd.
After being sent to Lyoko's forest region, the others head for the tower on their trademark vehicles. Along the way, they encounter a couple of Krabes. Ulrich slices one down the middle and Yumi takes care of the other. A Kankrelat shows up to attack Ulrich and lands a hit. It's destroyed just as quickly.
Back in the factory, Odd starts to lose his powers. He calls Jeremie to find out why. Jeremie isn't quite sure, but not too surprised either. As Odd continues fighting, Jeremie loses control of the tower he activated to XANA. The effects translate to Odd, who loses all of his powers from the possession. Instead of controlling Odd, XANA is just going to pump all of his energy until it kills him. Powerless, Odd is forced to run, losing his cell phone to Yolanda along the way.
On Lyoko, the group is informed of Odd's situation. Aelita and Yumi head to the mountains. Ulrich stays behind to guard the other tower. A Krabe is there, but it's easily destroyed by Ulrich. Three more Kankrelats arrive to join the fight. Ulrich uses his Overbike to wipe out all three in a single hit.
In the mountain region, XANA has made the entire region invisible. All that can be seen is the fog. Similarly, his monsters are protected by the same effect. An unknown number of Hornets take out Yumi's vehicle, causing both her and Aelita to plummet. Guided by Jeremie, they're able to catch a ledge. He continues to guide them across the unseen landscape. Eventually, they get close to the tower. This is when the invisible Hornets come back for round two. Yumi covers Aelita as she heads to the tower. The Hornets manage to force Yumi off the edge, but she grabs on just before falling.
Back in the factory, Odd is eventually knocked out by Yolanda. Knowing that he'll die anyway, she heads back to the corridor. Aelita manages to shut down the tower just before he dies.
Back on Lyoko, the landscape and monsters reappear. There was ground under Yumi the whole time, it seems. The two Hornets, now visible, are destroyed by her. Jeremie brings up the overboard and they head back to the first tower.
In the forest, Ulrich has triplicated himself and is dealing with a Block, a Krabe and three Kankrelats. The Block is the first to go. The Krab goes next. Alone, the three Kankrelats are no match for Ulrich. His two clones take out two in a flash. They torture the third by kicking it into the air before removing it. Aelita and Yumi arrive as he fuses himself into one person again. When Yumi asks where the monsters went, Ulrich just asks "What monsters?"
Back in the lab, Yolanda arrives to cause trouble. Odd arrives, too, but isn't any match for her. Both Jeremie and Odd are about to get blasted when Aelita shuts the tower off. Yolanda's possession subsides and she collapses.
Back at the school, Sissi is trying to explain what happened, making sure to include the weird stuff in her story. Neither the principal nor Jim believes her. The whole story reminds Jim of when he used to work in a psychiatric hospital. As always, he'd rather not talk about it. The others show up with Yolanda so Sissi doesn't seem quite as crazy. Yolanda remembers nothing and believes Aelita's story of how she went out to get some air through the window. As the others walk off, Sissi demands an explanation. Odd wards her off by commenting her on her extra five pounds. Sissi is still in denial about it. Odd tries to tell her that no one's perfect, to which she responds by pointing out his scrawniness. Odd still insists he's svelte, getting a good laugh from the others. The episode ends on that.
This episode contains examples of:
- Alpha Bitch: Sissi is concerned by Yolanda's assessment of her weight being 5 pounds more than normal, and gets made fun of by the gang because of this.
- Alternate Identity Amnesia: Yolanda gets amnesia after XANA leaves her body, much to the relief of Jeremie and the crew.
- Body Surf: XANA does this once again, but this time with the school doctor; Yolanda. This is a comparatively sloppy attempt to kidnap Aelita compared to previous attempts, and it makes XANA seem desperate more than anything.
- Cell Phones Are Useless: Two cellphones die in this episode; Ulrich's and Odd's.
- Continuity Nod: Aelita notes than this isn't the first time XANA has made the terrain disappear.
- Elevator Failure: Jeremie uses the Super computer to intentionally refuse the elevators' call when XANA attempts to call for it.
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Hollywood Pudgy: Sissi is revealed to be 5 pounds overweight, despite looking the same as she usually is. Aelita outright lampshades this and the rest of the gang follows through with fat jokes at Sissi's expense. - Insistent Terminology: Odd insists he's not scrawny, he's svelte.
- Out-Gambitted: XANA wises up to Jeremie's specter tricks, and takes over his activated tower to drain Odd of his life force.
- Power Echoes: Odd's voice and XANA's grunts.
- Running Gag: The whole story of Yolanda getting posessed reminds Jim of when he used to work in a psychiatric hospital. As always, he'd rather not talk about it.
- Shock and Awe: Present and Accounted for when XANA!Yolanda fights Odd.
- Shout-Out: To Street Fighter; Odd does the "Hadouken" move to project an energy ball.
- Start X to Stop X: Jeremie, for the first time, activates a tower in order to make Odd be as immortal as XANA is.
- Superpowers For A Day: Odd asks to be the test subject to "Jerimification", which digitises Odd for a short time, essentially making him as immortal as XANA is.
- The Worf Effect: For once, weaponized against XANA; Odd turns into a superpowered specter to fight XANA Yolanda. At his peak power levels, Odd fights very well against her.
