After a trip to Sector Five, Jeremie believes he has the data necessary to cure Aelita's virus. While Jeremie and Aelita work on the cure, Ulrich, Yumi and Odd attend a rock climbing contest in the gymnasium. It is seen that despite Ulrich's hestitation, his friend still drag him toward the gymnasium.
The contest starts with Herb versus Odd, results Odd's victory. William later challenges Ulrich despite his obvious reluctance. Not wanting to be humiliated in front of his friends, especially Yumi, Ulrich accepts the challenge. Just as his friends push him to keep going, Ulrich gets dizzy and fall afterwards, which makes Yumi realizes that he must have vertigo - a symptom that makes the patients feel the world or them-self is spinning. Ulrich runs away with embarrassment.
Meanwhile, Jeremie finds an anti-virus program and gives it to Aelita. Despite some problem with the application, it seems to work when Aelita remains safely. However, a bug in the program causes her to turn invisible right after Jeremie announces the good news to Yumi and Odd.
Back to Ulrich's escape from the gymnasium, Yumi and Odd found him sitting and sulking in the woods. They try to cheer him up with the news from Jeremie, but the conversation is interrupted by a possessed pack of wolves, which are from X.A.N.A.'s latest attack. The three run away with horror and face a rock cliff. While the other two climb up successfully, Ulrich, once again, faces his vertigo but still manages to reach the top thanks to Yumi. Sooner than expected, a wolf appears in front of their faces three seconds later. The wolf pushes Ulrich and makes him fall. He later on discover that the wolves are just illusions and announce it to Odd and Yumi. However, after getting rid off the illusions, some of the wolves are still alive.
Aelita insists Jeremie to deliver her back Lyoko to deactivate the tower. after they receive a phone call from Yumi. When she arrives, it occurs that the mentioned error in the anti-virus program blocks Aelita from entering any tower in Lyoko, resulting her inabillity to prevent 's X.A.N.A.'s attack. Aelita later faces a Scyphozoa and easily freezes the creature.
After hearing Jeremie's request for Aelita's aid, Ulrich orders Yumi and Odd to help Aelita while he fights the wolves by himself. After tries kicking them with a stick, Ulrich runs toward the city to seek for help. He contacts Jeremie and gets a sudden attack from the back by a wolf, which is seen by Jeremie through his computer screens.
Meanwhile, Yumi and Odd are transferred to Lyoko and seek for the tower, but are blocked by a Megatank. Yumi got devirtualized while Odd manages to defeat the creature. For Aelita, after the Scyphozoa, she encounters the Hornets and runs away. Accidentally, she returns to the spot where she freezes the Scyphozoa. The creature unleashes itself in front of a horrified Aelita, and hornets reach her from the back. While Aelita is literally hung up, Odd reaches her spot, and escape from the hornets by swimming under water. He frees Aelita from the Scyphozoa by his Laser Arrows.
Jeremie still work on his anti-virus program with Yumi along his side, and both of them saw Ulrich collapse inside the factory. Yumi attempts to help Ulrich, but the anti-virus program is stopped at the same time, so Jeremie stops her. Eventually Aelita deactivates the tower and Jeremie uses Return to the Past.
Back to the day before, while William mocks Ulrich for being dizzy, Ulrich revenges by announcing William's fear of spider and calls him Spiderman.
- The original French name for this episode is Vertige.
- Chronologically, this episode takes place after both Temptation and A Bad Turn, however it was aired before either.
- It is also revealed that William is afraid of spiders.
- Odd makes a reference to Fantastic Four when he compares Aelita's invisibillity to Sue.
- Yumi says "Konnichiwa" in her cell phone's voice mail message when she would have actually said "moshi moshi" as in the Japanese language they use that phrase to answer the phone.
The original summary can be found here.