GLaDOS - Plot in Portal 2

Portal 2

In Portal 2, GLaDOS initially resumes her role as test monitor. This time, she is more passive aggressive and makes no attempt to hide her contempt and hatred for Chell. However, a plot twist occurs when the bumbling personality core Wheatley convinces Chell to perform a core transfer, allowing him to forcibly take GLaDOS's place as head of the facility. At this point he almost immediately becomes power-mad and decides to test or kill Chell and GLaDOS, throwing the arch-enemies into the bowels of the facility. With no other choice, Chell and GLaDOS — now reduced to a simple core powered by a potato-battery, decide to team up to prevent Wheatley from completely destroying the facility in his incompetence. Chell and GLaDOS are successful in defeating Wheatley; Chell allows GLaDOS to retake her role as head of the facility and GLaDOS saves Chell's life. She then decides to let Chell leave the facility, determining it is too much effort to kill her, and throws out the Companion Cube Chell had from the first game as a parting gift. Portal 2 also reveals background information about GLaDOS. It is disclosed she was created from the personality of Caroline, an assistant to Aperture Science's CEO, Cave Johnson, who left her in charge of the facility via a mind-to-computer transfer after his death. After being dethroned by Wheatley, GLaDOS begins to regain some of her humanity and becomes kinder to Chell. However, at the end of the game GLaDOS apparently chooses to delete this aspect of her personality and return to her sociopathic persona.