Portal 2 is set many years after the end of Portal. Chell is still in Aperture and she still wishes to escape. GLaDOS rises from the dead while new characters are introduced such as the Personality Sphere Wheatley and Aperture's founder Cave Johnson.
Chell has awoken from stasis after many years. She must navigate the now-dilapidated Aperture Science Enrichment Center with the portal gun while the facility is rebuilt by the reactivated GLaDOS, an artificially intelligent computer. The storyline introduces new characters, including: Wheatley (Stephen Merchant) and Cave Johnson (J. K. Simmons). Ellen McLain reprised the role of GLaDOS.
The first act of the game reprises the same concept as the first with Chell having to pass all of GLaDOS' tests while the second act has GLaDOS and Chell teaming up against Wheatley who has taken control of the facility. The game ends with GLaDOS taking control of Aperture and finally letting Chell go.