Jeremy works tirelessly to materialize Aelita into the real world and stop attacks caused by X. A. N. A. Jeremy is aided by his three friends Odd Della Robbia, Ulrich Stern, and Yumi Ishiyama, who are virtualized into Lyoko in order to save both worlds from the sinister virtual entity. They achieve this by escorting Aelita to various towers on Lyoko, which serve as interface terminals between Lyoko and Earth, and having her deactivate the one that X. A. N. A. is using to access the real world. Once the tower is deactivated, Jeremy is able to launch a "Return to the Past" program, which sends anyone scanned into the Supercomputer's memory back in time, whilst retaining memory of the other timeline, to undo any damage caused by X. A. N. A. (the only exception of this are any deaths caused by the attack, which would carry over even with the time reversion). In "Code: Earth," Aelita is finally materialized, but the group discovers that X. A. N. A. had planted a virus inside of her that will kill her if the Supercomputer is deactivated. They realize that they cannot destroy X. A. N. A. completely, or Aelita will be destroyed along with it.