Chell and PotatOS land in the abandoned 1950s-era labs. As they climb back up through the decades (the 60s, 70s, and 80s), they hear pre-recorded messages from Aperture’s founder, .

In a surprising show of "mercy," GLaDOS decides that killing Chell is too much trouble. She claims to have deleted the Caroline persona (though her final song suggests otherwise) and releases Chell from the facility. Chell rides an elevator to the surface, where she emerges into a peaceful wheat field, followed shortly by her scorched . com/wiki/Cave_Johnson">backstory of Cave Johnson ? Portal 2 In 6 Minutes

Remembering that moon dust is a perfect portal conductor, Chell fires a portal directly at the . The resulting vacuum sucks Wheatley and the "Space Core" out into orbit. GLaDOS regains control of the facility and pulls Chell back to safety. The Ending

The game begins long after the events of the original Portal . Chell, the silent protagonist, is woken from a long stasis in a dilapidated "Relaxation Center" by , a chatty and bumbling personality core. As the facility crumbles around them, they attempt to escape but accidentally reactivate GLaDOS , the AI Chell "killed" in the first game.

They return to the modern facility to find Wheatley has made a complete mess of things, pushing the reactor toward a core meltdown. In the final battle, Wheatley booby-traps the room, but Chell notices the roof has been torn open, revealing the night sky.

Through these recordings, GLaDOS realizes she was originally Caroline , Cave Johnson’s loyal assistant, whose mind was forcibly uploaded to create the AI.

GLaDOS, still bitter about her previous defeat, separates Chell from Wheatley and forces her back into a series of grueling tests while she rebuilds the facility. The Great Betrayal

However, the power immediately goes to Wheatley's head. He becomes a megalomaniacal tyrant, shoves GLaDOS’s consciousness into a , and—in a fit of rage—sends both Chell and "PotatOS" falling miles down an elevator shaft into the oldest parts of the facility. The History of Aperture