Obstinacy

Aelita dreams of her long-lost mother, Anthea. She wakes up and goes to see Jeremy, but finds Laura there with him, both working on the virus to destroy the Cortex. A hurt Aelita leaves, and Laura smugly denies that there was anyone at the door. Jeremy and Laura finish the virus and the group plans to implement it that afternoon, but Odd gets detention and Ulrich sprains his ankle, forcing both of them to opt out. William, Aelita and Yumi go in.
By the time they reach the center of the Cortex, only Aelita remains. She accesses the mainframe and finds a webcam stream of Tyron working in his lab at that very moment. She observes the stream for a minute, telling Jeremy what's going on, then moves to infect the Cortex with the virus. But then she looks up, and sees her mother in the office with Tyron, also working on part of the project. After a moment of confusion, Aelita firmly insists on destroying the Cortex and XANA along with it, but Jeremy and the others unanimously decide to abort the mission for now as there is proof that Aelita's mother is indeed alive and a chance of reuniting her with her daughter. Aelita comes back to Earth, upset about not destroying XANA, but her friends convince her that the risk was worth it. And assure her that if XANA gains too much power, they will destroy it and the Cortex immediately; no questions asked.