SPOILERS AHEAD!
YOU HAVE BEEN WARNED!
Overview
First hinted in the update made to Portal in March 2010 as part of the Portal ARG, it was announced on March 5, 2010 to be released in fall 2010,[5] but was later announced on June 9, 2010, as delayed until an unspecified date in 2011,[6] until it was said to be released on February 9, 2011.[7] This date was again delayed to April 19.[8] Portal 2 was previewed in the twelve-page cover story of the April 2010 issue of Game Informer, revealing some plot details and new gameplay features.[9] It was also confirmed that GLaDOS was indeed still alive, and would return as the main antagonist.[10] In addition, Game Informer and other sources confirmed a co-op mode for up to two players with its own separate campaign.[10] The co-op campaign was said to have separate credits and would take place after the single-player story.[11][12] Valve was also scheduled to unveil the Portal 2 World Premiere on June 14, at their E3 2010 press conference,[13] but later canceled the showing of Portal 2 on the 14th through a humorous e-mail, to be replaced with a "surprise". The game was shown in the form of a demo at Valve's own booth instead,[14] and on June 15, the first Portal 2 trailer was shown during the Sony press conference, with the "surprise" apparently being its release on the PlayStation 3 console, which was originally not the case.
Chapter 1: The Courtesy Call
Fifty days after she is put in stasis, Chell is awakened by an unidentified announcer. In compliance with "state and federal regulations," Chell is instructed to perform a mandatory physical and mental wellness exercise which is used to teach the player the standard controls. Chell is then instructed to return to bed. Between 50 and 50,000 years later (the exact time is never made clear), Chell is awakened again. During this second awakening, the announcer glitches saying that they "have been in suspension for..." followed by a glitched message repeating nines. Afterwards, Chell meets Wheatley for the first time. Chell learns that the facility's reserve power has been lost and is instructed to prepare for reactor core meltdown. Wheatley, fearing he will be blamed by "management" for the incident, plans to escape. He smashes the chamber through a wall and tells Chell to look for "a gun that makes holes." The Aperture Science facility is overgrown and badly damaged. During the escape attempt GLaDOS is accidentally reawakened by Wheatley, who is separated from Chell and GLaDOS promptly resumes forcing Chell to complete test chambers. The test chambers and Central AI chamber are the same from Portal, albeit heavily damaged and decrepit.
Chapter 2: The Cold Boot
Chapter 2: The Cold Boot
<>GLaDOS introduces new tests. They primarily include Thermal Discouragement Beams and Aerial Faith Plates. This chapter includes GLaDOS' Test Chambers 1 to 8. Test chamber 1 is the first chamber to use the Thermal Discouragement Beam alongside with portals. GLaDOS claims to need to start the facility back up while she performs the test, and then tells Chell to pace herself because of a numerous amount of tests. Test chamber 2 introduces Discouragement Redirection Cubes as well as the ability of the cubes to press buttons alsongside of redirecting lasers. Upon completing the test, GLaDOS tells Chell that the test said that "she was a horrible person". Test chamber 3 introduces Discouragement Redirection Cubes alongside with portals to complete the test, alongside with being the first chamber to use 2 lasers. After the test, GLaDOS congratulates Chell on "beating the odds" and not being extremely skinny after emerging from suspension. Test chamber 4 introduces the ability for lasers to activate moving platforms, as well as the feature of Chell needing to jump over the beam so that she doesn't get pushed off of the platform. Before the test, GLaDOS clears away some fallen panels that block the way and tells Chell to go slowly. At the end, GLaDOS tells Chell that she "doesn't have to go that slowly." Test chamber 5 introduces the Aerial Faith Plates. In this chamber, Chell needs to time her jumping on a Faith Plate to the cube bouncing on a Faith Plate so that she gets the cube. Test chamber 6 introduces "Advanced Aerial Faith Plates", which is a conjunction of Faith Plates and portals to get Chell to a button and to maneuver the cube to the button. GLaDOS indirectly calls Chell "smelly garbage standing around and being useless", which she apologizes for (sarcastically) at the end of the test. Test chamber 7 is the only chamber in the game to have the Companion Cube, which is not as heavily stressed upon as in Portal. In fact, GlaDOS fizzles the cube several times before she lets Chell use it to solve the test. The chamber requires Chell to fling to activate a door. The testchamber also has a broken emancipation grill, which means that Chell can smuggle the Companion Cube into the exit. If Chell does this, then GLaDOS fizzles the cube. Test chamber 8 introduces the concept of fizzlers mid-level, in which Chell has to portal through a small gap and use a redirection cube to shoot a laser through a fizzler. GLaDOS mocks Chell once again before leaving, saying that the turbines have broken down. It is the last chamber of the chapter.
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 (presumed to be Chell's birth parents). This chapter includes GLaDOS' Test Chambers 9 to 17.
Chapter 4: The Surprise
Chell is given a "surprise" as hinted by GLaDOS, which is the complete absence of one, except for a puff of confetti. 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. She decides to "call" Chell's parents, only to fake a voicemail message saying that her parents don't love her. This chapter includes GLaDOS' Test Chambers 18 to 21 out of 22 total. (Wheatley breaks in at 21.)
Chapter 5: The Escape
Before GLaDOS can kill Chell, she and Wheatley escape. GlaDOS attempts to lure Chell to her death by leading her into a misleadingly easy test chamber. If the player chooses to enter, the walls will close in and GlaDOS will activate the neurotoxin, killing them. Otherwise, the escape will continue as normal. They eventually sabotage GLaDOS' turret and neurotoxin manufacturing facilities before confronting GLaDOS. Chell and Wheatley force a core transfer on GLaDOS so that Wheatley can take control of the facility and he and Chell can escape. GLaDOS' head is abandoned on the floor, and Wheatley—manically happy with his newfound competence—activates the lift to let Chell leave. Unknown to he or Chell, however, the body which affords Wheatley this competence is fully instilled with a will and a set of goals of its own, and as its programming aggressively subsumes Wheatley's better nature, he becomes reluctant to leave it. Uncertain what he is feeling, he projects the source of this uncertainty onto Chell; he asks why "(they) have to leave right now" after "(he) did all this." Wheatley's mood is darkened further when GLaDOS speaks up, stating that he never did any work at all. She spitefully praises Chell to Wheatley, and his insecurities—hinted at before—blossom into egotism. He attempts to assert his superiority over GLaDOS—by isolating her personality to a miniature core dependent on a potato battery for power—and resentfully berates the mute Chell for "bossing him around." As he continues his tirade, GLaDOS realizes that she has met him before. She recalls her distant past, where Aperture Science created Wheatley with the express purpose of impairing GLaDOS with self-destructively stupid ideas. Finding herself once again incapacitated by Wheatley, GLaDOS bitterly abuses him as "the moron they built to make (her) an idiot." Wheatley is humiliated and furious. He throws GLaDOS into the lift with Chell and beats the lift into the floor of the control room, until—unexpectedly—it detaches from its station, and plunges into the bowels of Aperture Laboratories.
Chapter 6: The Fall
Chell and GLaDOS fall down the disused length of what clearly used to be a much larger elevator shaft. At fully four kilometers deep, the fall gives the two plenty of time to come to terms with their new situation in regards to each other. GLaDOS is unenthusiastic about their chances of surviving their trip underneath the laboratories; she herself is unaware of how far down Aperture Science really goes and has no idea what to expect. Chell's fall is finally broken by layers of planking, lain down at some time in the past, either because the area was abandoned, or it was to stop debris from injuring anyone below the mouth of the shaft. The wood is rotten and soft, and the rest of the impact is absorbed by Chell's long-fall boots, leaving her concussed but, fortunately, not fatally injured. After a short space of time, Chell regains consciousness, and is greeted with the inexplicable sight of GLaDOS being menaced by a large crow. A long splinter of metal from the casing of the elevator has speared GLaDOS potato—and has prevented it from smashing on the packed gravel floor—but it has also brought the potato to the notice of the crow. The crow abducts the potato, with the AI still attached to it, and flies off. Chell is left alone to wander Test Shaft 9 from the 1950's, back when Aperture Laboratories was instead known as Aperture Science Innovators. Chell is guided by pre-recorded messages by Cave Johnson (the former CEO of Aperture Science) and occasionally, his assistant, Caroline. Chell activates the flow of the Repulsion Gel, and begins testing in the first Enrichment Sphere, where the Repulsion Gel, the first design of boxes, buttons and switches is shown. She makes it through the 1950's testing track, and heads up to the 1970's one.
Chapter 7: The Reunion
As Chell is trying to find her way into the 70's testing track, she manages to find GLaDOS being eaten by a crow. With no other choice, Chell skewers GLaDOS onto her Portal Gun and continues through the Johnson-era test chambers with the AI in tow. She activates the Propulsion Gel flow and uses both Repulsion and Propulsion Gels to solve the test. Meanwhile, ancient recordings of Cave Johnson's self-confident rambling continue, as he relates anecdotes, argues with his staff, and exhorts the test subjects to keep going. Then, for first time since Chell locates GLaDOS, he addresses the recorded ghost of Caroline, and GLaDOS speaks—blurting out the words "Yes sir, Mr. Johnson!" before she can understand what she is doing. GLaDOS is panic-stricken, and, in her heightened emotional state, overdraws from her fragile potato battery, causing her to hard-shutdown and crashing her system. Chell is again left to traverse the old testing areas alone. As Chell makes her way up the condemned Enrichment Spheres, she activates the flow of a third gel, Conversion Gel. A subdued GLaDOS comes back online, and the two quietly bear witness to the fact, revealed through Cave Johnson's increasingly bleak recordings, that Aperture Science lost money over the years, going from using Olympic stars and astronauts as test subjects to homeless people, and eventually just using their own employees. GLaDOS also feels that she "knows" Caroline, and must've realized she was Caroline 1. The quality of the test chambers falls dramatically as the construction dates advance. Cave Johnson—still making recordings in the past—is now extremely ill from moon rock poisoning. We learn that, and Cave feebly confides in the recordings that he has set all his scientists to the task of storing a human consciousness in a computer. He states that—if he dies before they make it a feasible procedure—that he leaves the entire facility to Caroline and says that she is to be uploaded into the system, instead, whether she wants it or not. Chell connects the last two experimental fluids to the uptake valves located at the twin of the first quarantine hatch, this one located at the top of the condemned section. GLaDOS quietly says goodbye to her old boss. as it is implied that GLaDOS is in reality, Caroline uploaded to the machine, with her old memories suppressed.
Chapter 8: The Itch
Chell and GLaDOS return near the surface to Wheatley's redesigned Enrichment Center, while making the gels available in the Enrichment Center. 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 known as "Frankenturrets" by developer commentary. 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 stolen from GlaDOS' collection. After a few tests, Wheatley's quest for test-induced euphoria forces him into giving Chell more and more dangerous tests. Eventually, he plans to give them both a "surprise".
Chapter 9: The Part Where He Kills You
After several tests, Wheatley finds out about the Cooperative Testing Initiative 2 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. Wheatley attempts to stop them using a series of ill-executed traps, (poorly aimed Crushers, mistakenly using Defective Turrets, lack of forethought, and even trying to talk Chell into killing herself) which do nothing to hamper Chell's progress. 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 timed boss battle ensues. Chell redirects bombs to Wheatley as GLaDOS delivers corrupt cores. After attaching the 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. The Moon appears through a breach in the roof, allowing Chell to shoot a portal at its surface at what is likely the Apollo 17 landing site at Taurus-Littrow (Cave Johnson said prior that lunar dust was an excellent portal-conducting surface). The vacuum of space sucks Chell, Wheatley, the Portal Gun, Rick the Adventure Core, 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. Some time later, Chell wakes up in an elevator, as GLaDOS, ATLAS (Blue) and P-body (Orange) greet her. GLaDOS tells her that "being Caroline" taught her a valuable lesson - that Chell was her best friend. She says she also learned where Caroline lives in her brain, and then promptly claims to have deleted that part. Now back to her usual antagonistic self, GLaDOS concedes that killing Chell has proven to be difficult, and her life was a lot easier before Chell entered it, as well as calling her a "dangerous, mute lunatic". Therefore, she gives Chell her freedom, on the condition that she doesn't come back. As the elevator rises, an army of turrets sing an opera for Chell as she departs. After finally reaching the surface, Chell steps out from the elevator and into a golden wheat field. Suddenly, Chell's Companion Cube from the previous game, covered in soot from the incinerator, flies out of the elevator behind her and the door slams shut. During the credits, GLaDOS sings a song about the events of Portal 2, claiming that while she used to want Chell dead, now she only 'wants her gone'. However, the lyrics of the song hint that GLaDOS' feelings about Chell may be slightly more conflicted than she'd like to admit, and it appears Caroline may still have a place in her mind. After the credits, the picture zooms out and then it's possible to see that the credits were displayed in space on one of the computer monitors used in the observation rooms of various test chambers. Wheatley and the Space Core are floating around. Wheatley then gives a monologue (even though he is interrupted several times by the Space Core), saying that if he could see Chell again, he would apologize for being so bossy and monstrous to her. He then says "the end," and the scene fades into the main menu, where Wheatley and the Space Core are still in space in the background.