Code Lyoko

After an unexplained incident on Lyoko ends up devirtualizing Yumi without any cause, she is taken to the infirmary. After waking up, she attacks Yolanda and continues to act weird throughout the day, wanting to go to Lyoko with everyone else. Jeremie won't let them, though, because he wants to know just what caused her devirtualization. Meanwhile, on Lyoko, Aelita finds several Roachters guarding an orange sphere, which she calls a Guardian, and informs Jeremie.