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
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, . Portale 2
Wheatley eventually helps Chell escape the test chambers. Together, they sabotage GLaDOS's turret and neurotoxin production lines. They confront her in the central control room and perform a "core transfer," replacing GLaDOS with Wheatley. GLaDOS, still bitter about her previous defeat, separates
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. Wheatley eventually helps Chell escape the test chambers