Portal 2 takes place hundreds of years after the first game. Despite her apparent destruction at the end of Portal, GLaDOS remains functional. The player controls Chell, the same protagonist from Portal; retroactively patched just prior to the sequel's official announcement, the ending of the first game shows Chell being dragged away by an unseen figure with a robotic voice, where she has been placed in stasis over the years.[3] The game will again take place in the Aperture Science Labs, untouched by human hands but overrun by decay and nature.[3] The player will interact with many of the numerous personality cores (which were seen activating in the post-credits scene from Portal), which have become active in the intervening years, using the automated systems of Aperture Science to create their own microcosms within the facility.[3] The cores themselves are unable to move save through overhead rail systems. Chell is awoken by one of these, Wheatley, who has become concerned for the state of decay and seeks to correct it. Wheatley acts as the player's guide during the tutorial and initial stages. Soon, the two are introduced to GLaDOS, who is quick to accuse Chell of murdering her years ago.[3]
Two new characters will be introduced for the two-player cooperative mode, which will have its own unique plot and setting.[6] These two yet-to-be-named characters include a modified turret gun and a personality core; both units are bipedal and equipped with their own portal guns.[3] Though once part of the networked facility, they have become separate entities and are treated to similar abuse by GLaDOS while Chell is being put through a series of complicated test chambers.[3]