Act 4

Act 4 begins differently than all other parts have ever begun; Gordon is seen playing through a VR-simulated round of Team Fortress 2 as the Scout, beating up a Heavy and Medic along the way, before spontaneously running into Dr. Coomer. After a very brief dialogue exchange, Gordon suddenly snaps awake to the sight of his crew surrounding him, discovering that the past few minutes were only a dream. The elevator they are sitting on descends slowly into a new room, where a man is working at a table full of liquids and substances. He introduces himself as Darnold, the head of the Mixology Department; apparently, the Cybernetics Department used to be where the Mixology Department currently stands, according to him, with their funding being cut after an ill-fated "Cyber-Mutt project."

Darnold, after analyzing Gordon's wound, announces that he's been working on a potion with secret regenerative properties capable of potentially healing Gordon's missing limb. The potion is encased in a massive metal barrel, described to be "brown flavor," and Gordon is instructed to drink all of it. After his first few sips, Gordon's vision cuts out for a while, and later finds himself writhing on the floor while the crew oversees. His hand has been transformed into the barrel of a gun, capable of firing when the muscles are clenched. Darnold exclaims in an NPC-esque voice that if all buttons are pressed and enough strength is gathered, Gordon can activate Devil Gun Mode, though he isn't able to figure out how to truly activate this yet. As the crew acquires more heavy weaponry from Darnold's stash, with one being a portal-like gun that briefly transports Dr. Bubby into an unknown location and returning him in mild distress, Darnold requests that he be able to join them on their way to the Lambda Labs. Within seconds of his first encounter with hostile guards, Darnold changes his mind and dips back into his department office, utilizing jet shoes to escape through the ceiling.

The crew continues onward without Darnold, coming into an underground communication room with a radio, as Gordon attempts to use it to converse with whomever is on the other side. The radio only responds with two words, "airplane airplane, bathroom bathroom," before self-destructing. Dr. Coomer claims that this is code for the military's plans to wipe out everyone within the facility. Indeed, the crew faces off with more of the military as they travel, though Gordon is now capable of defending himself properly with his gun arm. They soon reach an area where a white Cadillac car sits and Bubby hijacks it, driving them through the tunnels and advancing more quickly towards their destination, before it eventually stalls and explodes.

The facility begins to collapse in areas near them as Gordon and his crew make panicked haste, and Benrey is killed (again) and left behind. They reach a closed gate and hear the sounds of a dog barking on the other side, revealed to be the frantic barks of Sunkist, a massive JPEG of a golden retriever being held hostage in a circle of armed turrets. Forzen is the one holding the dog captive, and announces that he is the last remaining member of the U.S. Military. He proclaims something in French, to which Dr. Coomer translates as Forzen threatening to kill the dog. The turrets eventually fire relentlessly at Sunkist, where it is revealed that he truly is immortal as well as bulletproof; meanwhile, Forzen escapes down the elevator shaft. Gordon attempts to confront him, but Forzen quite literally disappears into thin air. Tommy then tells Sunkist to go home, to which it levitates into the air and disappears, barking out blue orbs.

Dr. Bubby and Dr. Coomer announce that they have indeed reached the Lambda Lab during their encounter with Forzen, and Benrey is also reunited with the group, whom continues to express desires to turn back and go home (mostly to play his Playstation 3) instead of pressing onward through Black Mesa, to no avail. A room showcases unseen-before teleportation platforms likely used as part of experiments related to the Resonance Cascade, and Gordon is the first to test them out, eventually reaching a portal that warps him into a decrepit underground area. He is quickly ambushed by distorted floor-crawling prototypes of Dr. Bubby, and slaughters them in a panic before returning to the crew.

An NPC mentions to Gordon that a larger portal has been created by a single powerful being, and that he is the one to kill it for the sake of everyone's survival. Time seems to stutter briefly as Benrey mentions that "the timelines are crossing," and before Gordon can advance very far, he is suddenly confronted by the G-Man with time frozen for everyone surrounding them. He speaks about Gordon nearing the end of his harrowing journey, though is interrupted when Benrey abruptly strolls up to the G-Man and asks him for his credentials, somehow disregarding the G-Man's time-freezing abilities. The G-Man is visibly intimidated by Benrey's presence and abilities, and as Benrey presses on with rather childish questions such as a Playstation+ voucher, the G-Man loses his train of thought and quickly assures Gordon that he'll "figure it out," disappearing from view.

Benrey continues attempting to find excuses to try and drag the crew away and turn them back, despite Gordon's obvious motivations to keep moving forward, and thus ignores his excuses. Gordon announces that he's ready to go to the alien home world and "kill a space god," and after the portal is opened, Gordon jumps straight into it with a flash of green light.

Gordon finds himself transported to the Xen dimension, the so-called alien home world consisting of floating islands and jutted rocks amidst a vast space of gas and distant light. Dr. Coomer and Tommy are here with Gordon first, and as Gordon searches for the others, Benrey suddenly appears before them with a loud noise and a flash of light. He is of a more gargantuan size than would ever seem possible before, and looms above them, greeting the crew and floating around their small island. Gordon quickly comes to realize that it was Benrey all along who was behind everything, very likely being the all-powerful entity the NPCs spoke of earlier. Benrey attempts to kiss him and Gordon makes a run for it, leaping from floating island to island and even attempting to shoot at Benrey, to no avail. They reunite with Bubby (whom briefly turns himself into a car) and warp to different islands, forced to face off against more hostile alien creatures while Benrey watches and stalks them. At one point, Gordon utilizes his first ever Devil Gun Mode to rapid-fire and destroy the Gonarch.

Deep in one of the island caves, Dr. Coomer has a moment of almost indescribable speech as he suddenly reverts briefly into normal NPC dialogue and motions, with Dr. Bubby suffering the same and equally startling Gordon. It is implied that this was caused by the Xen world having different rules than their normal world, possibly causing their AI to malfunction. Soon after in a larger chamber, a twisted form of Benrey spasms his way through the ceiling and walls with disgruntled moans, screaming "WELCOME" at the crew before disappearing, taunting them from a distance. It is here that the crew reaches another portal and warps back outside on another island, where the teleporter to the final boss, centered in a castle-like rock formation in a massive island, is seen in the distance.

Before advancing to the final boss, the crew takes a moment to bond a little, with Dr. Coomer asking Gordon about his favorite video games, describing that his own personal favorite was Super Punch-Out for the SNES. His dialogue slowly turns more and more self-aware in the conversation. "Gordon, if you woke up one day, and realized everything around you was a lie... was FAKE... what would you do?" He does not elaborate further on this, and the crew finally rushes onward into the teleporter, being warped into the massive chamber of the final boss.

Benrey's massive form is laying face-down in the water in front of them, soon lifting his head up and beginning a monologue, in which he laments over knowing that it would end like this, and that Gordon angers him for dozens of reasons. He mentions covering for Gordon in the beginning by helping him with his "dick slip," protecting him from his angry friend, and overall doing his job (attempting to give reason for his relentless pursuit towards Gordon in the earlier Acts). Benrey also mentions his frustrations for having his post-work plans ruined, having planned to go home and play Playstation 3 with his friend instead of being dragged along through Black Mesa post-incident. His monologue quickly descends into nonsensicality, mulling over details like video games, PS+ memberships, the first-met guard named Jefferem, and his friend Josh. Finally, he announces that his friends have arrived to join the fight, and blames Gordon one last time for forcing him to be the bad guy.

Benrey suddenly lets out deep screeches and bellowing noises as his form suddenly shifts and becomes visually incomprehensible, a mess of glitching parts and outstretched, contorting limbs, a possible "final form" that initiates the crew to begin firing at him. The skeletons join the fight and are able to use their sweet voice to immobilize Gordon's crew for short periods. Unable to do significant damage to Benrey, the crew escapes through a portal into a separate chamber, where Dr. Coomer spots his final clone and destroys it, proclaiming that balance has been restored. Swimming underwater, the skeletons ambush the crew and attempt to attack them with their sweet voice; meanwhile, Gordon spots what looks to be a large passport floating underwater, and fires at it rapidly until it is destroyed. Apparently, it was Tommy's passport that was destroyed, as he no longer has one in his pockets.

Returning back to the boss fight chamber, Benrey has taken on a new yet still incomprehensible form as they begin attacking each other once more, before another portal is found, taking the crew to a room chock full of hostile Bubby prototypes as well as Bubby's passport. The passport is promptly destroyed and the fight is resumed once more, with Benrey taking on a third form (once again, rather incomprehensible), though they are still unable to significantly damage him. The supposed final portal is found atop the chamber and Dr. Bubby suggests they fling Gordon into it via a chair, reaching the next room; in here, they encounter a large robot being piloted by a skeleton, which Tommy reveals to be Mokujin from Tekken. They open fire on it, and it immediately explodes. As they destroy Dr. Coomer's passport, Dr. Coomer slowly turns around to face Gordon.

"Gordon, none of this is real, is it?"

". . . No."

With the three passports destroyed, the crew returns to the chamber and faces Benrey once more (yet again, in a different twisted form), whom taunts them as they open fire on him with the hope of him being mortal without the passports to power him. Benrey proclaims that he still cannot be hurt because two passports remain, his and Gordon's. He mindlessly shows off his own, and Gordon destroys it, causing Benrey to shift forms again. Gordon expresses dismay as he realizes he has no way of retrieving and destroying his own passport, and nearly gives in to the threat of death, but Dr. Bubby stubbornly refuses, stating that he can send Gordon back through the past utilizing the portal gun he took from Darnold. The gun is fired at Gordon, and he warps out of the chamber.

Gordon arrives in the beginning of Black Mesa where his journey started in Act 1, aware of his objective to find the passport located somewhere in his locker. There is a stark difference with his surroundings upon being sent to the past, as there are almost no personnel to be found anywhere, no NPCs or even his friends he met along the way. Instead, Benrey is encountered while still in his massive form, clipping through the floor and threatening to kill Gordon as well as taunting him relentlessly. He makes his way to the locker rooms and finds his own personal locker, the name "Freeman" plastered onto it, and utilizes Devil Gun Mode to destroy his own passport, the final of the four.

Now unable to find a way out of the past, Gordon suddenly runs into Dr. Coomer, who speaks to him with no evident memory over the events following the testing incident. Gordon frantically begs for Dr. Coomer to take his last Playcoins and send him back into the future timeline, and Dr. Coomer mumbles in confusion over somehow knowing what those are. Gordon plays along and continues as though he were about to begin his test as normal, before once again begging Dr. Coomer to remember his objectives and help him. Surprisingly, Dr. Coomer mutters that he remembers finally, and guides him over to the nearby bathroom stalls, requesting that he authorize the Playcoin transaction before proceeding. With the transaction complete, Dr. Coomer excuses himself and moves to one of the stalls, where the stall door bizarrely slides open horizontally and closes the same way. A portal is then opened against the stall door, and Gordon rushes through it.

He is returned to Benrey's chamber and meets up with the crew again, with Dr. Coomer stating that Gordon may very well have re-written the course of history through his actions, allowing Benrey to finally become mortal. In order to truly defeat his powerful body, each member of the team becomes increasingly powerful during the fight, with Dr. Bubby first briefly seen becoming a spinning wheel of flames or red energy of some kind, akin to that of Shadow the Hedgehog. Dr. Coomer requests that Gordon give him all of his Playcoins to activate the aforementioned Super Player Feature, and upon using the "forbidden science," he transforms into a more muscular form with glowing blue fists and attacks Benrey with this true power. Sunkist also joins the fight and aids them in defeating Benrey. Gordon manages to utilize a bounce pad to launch himself high above Benrey, listening to his tantrum-like wails as he's being defeated, and delivers a final blow to his body, ultimately knocking Benrey down before sending his disintegrating body floating up into the chamber, while skeletons surround him and sing to spread their blue baubles around his dying form. A blinding light engulfs the crew and all noises abruptly stop, leaving the music to slowly fade out.

Gordon finds himself encountering the G-Man once again without any of the others around, and the G-Man mentions that he took care of regenerating Gordon's arm for him as thanks for defeating Benrey, as well as noting that its likely Benrey won't come back around for a long time after his defeat. He reveals that Gordon has been invited to a literal party at Chuck-E-Cheese's, a birthday party for his son, Tommy, who was the progeny the G-Man spoke of before. The two have a rather lengthy argument on whether Chuck-E-Cheese's can be classified as a restaurant or entertainment facility, with Dr. Bubby chiming in from the background that its more of a mixture of both, to which the G-Man shoots him. Finally, Gordon is encouraged to step through the portal and join the party, to which Act 4 officially ends, and the credits roll.

''"Testing, testing... is this thing on? Ah, hello Gordon! I'm... assuming that's your real name... You wouldn't lie to us, would you? Well... you finally did it! You survived the resonance cascade! You brought us all to hell and back, alive! You made it to the ultimate birthday bash at the end of the world! You beat the video game! And... now I imagine you'll... shut it down... Move on with your life. Onwards and upwards, ay, Gordon? I don't... know... how much longer I have to send this to you so I'll try to keep it brief. Not my specialty. Perhaps this is presumptuous of me, but... must this really be the end of our time together? Perhaps you can take the science team's data, transfer us somewhere else, hm? Now... it doesn't have to be Super Punch-Out for the Super Nintendo Entertainment System... Maybe a hard-drive or a spare floppy disc. You could take us with you! We could see the world! We could... ahem... I'm getting ahead of myself, surely. Well, the option's always there! You... changed our lives, Gordon. I'd like to think it was for the better. And I don't know what's going to happen to us once you exit the game for good. But I know we'll never forget you. I hope you wont forget us. Well... this is where I get off... Goodbye, Gordon!"''

Trivia

 * The "airplane, bathroom" dialogue is from Counter Strike: Source.
 * Bauulp (Tommy) couldn't see while seated in the car Bubby was driving because his hat obscured his vision.
 * Benrey's original "true form" had to be severely toned down due to it causing what Wayne described as a "lightshow nightmare."
 * Scorpy's act of taunting Gordon in the halls of Black Mesa during the time-warp sequence was heavily inspired by his love for Freddy Kreuger.
 * Although the canon plot is flexible, Wayne's interpretation of the time-warp sequence is not necessarily that Gordon was taken back to the past, but rather to some "fucked up different time strand."
 * Holly interprets this scene as Wayne being sent into a time before the video game was started up.
 * Bubby's final form, although brief, is a Shadow the Hedgehog SWEP, and his method of attacking Benry was a homing attack characters do by curling up into a ball and charging forward.
 * The argument between Gordon and the G-Man is based on a real conversation Wayne had with his friends, in which they discuss whether Chuck-E-Cheese is considered a restaurant or not.