Portal 2 storyline

This article describes the Portal 2 storyline, chapter by chapter.

Portal 2 almost directly follows the events of Portal from Chell's perspective, although being set thousands of days after the events of Portal.

Prologue
Fifty days after the events of Portal, Chell is reawakened by an unidentified announcer. In compliance with state and federal regulations, Chell is instructed to perform a mandatory physical and mental wellness exercise. Chell is then instructed to return to bed.

Chapter 1: The Courtesy Call
Set thousands of days after Portal. The announcer wakes Chell up once more, and tells her that she has been in suspension for "99999-" only to meet Wheatley and helps him escape with her. The original Portal chambers are reintroduced, only damaged and with plant overgrowth sprawling along the walls. They are guided by the same announcer, using pre-recorded messages.

At the end, GLaDOS is accidentally reawakened and starts building new test chambers.

Chapter 2: The Cold Boot
GLaDOS introduces new tests. They primarily include Thermal Discouragement Beams and Aerial Faith Plates.

Chapter 3: The Return
Chell is put through more tests. The Hard Light Bridge and turrets are introduced.

Meanwhile, Wheatley formulates a plan to escape. GLaDOS spouts out information regarding the building, as well as attempting to trick Chell once more. GLaDOS also mentions of finding two people with Chell's last name, coincidentally a man and a woman.

Chapter 4: The Surprise
Chell is given a "surprise" as hinted by GLaDOS, which is the absence of one.

Meanwhile, GLaDOS once again attempts to make Chell stop by making her feel bad, especially now GLaDOS decides to include Chell's unknown parents into their conversations.

Chapter 5: The Escape
Before GLaDOS can kill Chell, she and Wheatley escape. They eventually sabotage GLaDOS's turret and neurotoxin manufacturing facilities. Chell and Wheatley force a core transfer on GLaDOS so that Wheatley can take control of the facility so they can both escape.

However, Wheatley becomes enraged when GLaDOS tells him that he did nothing and that Chell did all the work. He then traps GLaDOS in a potato battery. Afterwards, GLaDOS explains that the scientists of Aperture science created Wheatley mainly to slow GLaDOS down before the morality core was created to stop her from killing the humans. He was made to produce bad ideas. GLaDOS takes it too far and calls him a moron, prompting him to throw GLaDOS into the lift with Chell and smash on it with his fist, screaming "COULD A MORON SMASH YOU INTO THIS PIT?!", until it breaks and goes into freefall, deep into the bowels of Aperture Laboratories.

Chapter 6: The Fall
Chell and GLaDOS fall down into Cave Johnson's old test areas, back when Aperture Laboratories was instead known as Aperture Science Innovators, and get separated from each other. She is guided by pre-recorded messages by Cave Johnson and occasionally, his assistant, Caroline.

Chambers in here involve the Repulsion Gel and the first design of boxes, buttons and switches.

Chapter 7: The Reunion
Chell managed to find GLaDOS being eaten by a crow. With no other choice, Chell installs (stabs) GLaDOS onto her Portal Gun and continues through the Johnson-era test chambers with the AI in tow.

As she listens to more of Cave Johnson's recordings, GLaDOS recovers the long-suppressed part of her personality based on Johnson's faithful assistant Caroline.

Chapter 8: The Itch
Chell and GLaDOS return near the surface to Wheatley's redesigned Aperture Laboratories. Wheatley has taken control, but in his incompetence has failed to maintain the facility's nuclear reactors which are now in meltdown. Instead of properly maintaining the facility, Wheatley has been busy with his own creations such as the cube-turret hybrid popularly known as "Franken-cubes" and "CubeTurrets".

GLaDOS attempts to destroy Wheatley with a logical paradox, but fails due to Wheatley's already-poor grasp of logic. The mad AI forces Chell to go through his own ineptly designed test chambers, followed by more lethal chambers stolen from GLaDOS' collection.

Chapter 9: The Part Where He Kills You
After several tests, Wheatley finds out about the Cooperative Testing Initiative and takes it upon himself to kill the two. Chell manages to escape thanks to her skill with the portal device and a timely splatter of Conversion Gel.

As they make their way through the maintenance areas, the two come across a cache of un-incinerated corrupt personality cores. GLaDOS makes a plan to force another core transfer in order to return back to her original body, as well as making a deal to release Chell once they do so. Upon reaching Wheatley's chamber, a battle ensues. Chell redirects bombs to Wheatley as GLaDOS delivers corrupt cores. After attaching three cores, Chell increases Wheatley's corruption to one hundred percent. A core transfer takes place but results in another stalemate. Chell reaches for the Substitute Stalemate button, but Wheatley expected this and placed bombs as booby-traps.

Chell gets thrown across the room as the reactor meltdown enters its final phase, shaking the chamber apart. A full Moon appears through a breach in the roof, allowing Chell to shoot a portal at its surface (Cave Johnson said prior that lunar dust was an excellent portal-conducting surface). The vacuum of space sucks Chell, Wheatley, and the Space Core through, as Chell hangs onto Wheatley's tethered core to survive. Unseen, GLaDOS successfully performs the core transfer and stabilizes the reactors. She knocks Wheatley out into space and drags Chell back to safety before closing the portal.

Trivia

 * This chapter is only given a full name when it is reached; before that it is only known as "The Part Where...".

Chapter 10: The Credits
Chell wakes up in an elevator, as GLaDOS tells her that "being Caroline" taught her a valuable lesson. She originally considered killing Chell for what she has done to her, but instead decides to transport her outside of Aperture and demands that she "never return", for the sake of not bothering her again. There the co-op bots make an appearance with GLaDOS.

The elevator rises and Chell meets singing turrets along the way. Finally reaching the surface, Chell gets thrown out of the elevator, into the fields. Unexpectedly, the Companion Cube makes an appearance, getting thrown out of the outhouse looking partially burned.

Co-op campaign
The co-op campaign is set after the events of Portal 2. In it, two testing androids of the Cooperative Testing Initiative carry out a series of tests in 4 different chapters, each consisting of at least 10 test chambers. At the end of each chapter, GLaDOS sends the androids outside of the testing chambers and into the facility itself, claiming their help is needed to retrieve several Compact Discs "innocently" left lying around by the humans. In reality, she appears to be using the androids to help her gain control of the facility. After each out-of-chamber task, both androids are self-destructed.

After finishing the 4th set of test chambers GLaDOS instructs the two androids to help her find human test subjects trapped somewhere in the facility. After a series of obstacles outside the facility, including inside several old Aperture Science Innovators test chambers, the androids find and unlock a massive vault door leading to a huge chamber housing hundreds of human test subjects suspended in individual stasis chambers. GLaDOS then self-destructs both androids and the credits roll, showing GLaDOS scanning the identities of the test subjects and making remarks about them, both positive and negative. Though in the end it turns out she is just talking about one test subject.