The Enfield Haunting (2015)

S2E18 Vertigo

After returning from the Carthage Region, Jeremie is confident he has the information needed to develop a cure for Aelita's virus. While they focus on this, Odd, Ulrich, and Yumi head to a rock climbing competition. Odd easily outpaces Hervé, but William taunts Ulrich into joining the race, even though he seems hesitant. During the competition, Ulrich becomes dizzy and tumbles, prompting Yumi to realize he must be suffering from vertigo. Embarrassed, he quickly leaves the scene. Back with Jeremie, he successfully creates an anti-virus for Aelita, but when applied, it initially works before causing her to turn invisible. To make matters worse, she can't access the towers on Lyoko, leaving her unable to stop Xana's latest threat: a pack of wolves targeting Odd, Ulrich, and Yumi.