The Master Chief is in a dark room and conversing with a disembodied voice, his armor scored and bloodied on it. The voice asks him how he got there.
Miranda studies the sample they recovered from a Forerunner lab and converses with a biologist, Janine, over how the spores seem to have reactivated. Janine leaves Miranda to work in peace, but it is evident something is not right and she attacks a coworker, stabbing him with a pen in the neck.
Kai leads the SPARTAN-IIIs into battle but half of them don't even make it out of the Condor. They engage a Covenant corvette but are running out of ammo, even though a larger UNSC fleet arrives the odds are not in their favor. The Master Chief has the option of staying wide of the battle to make it to Halo. Parangosky demands him to complete his mission, but he decides to assist the SPARTAN-IIIs. He lands on the ship and clears the path, directing them to evacuate.
Laera and Kessler are imprisoned in a brig and Ackerson ends up next to them. They realize a prisoner - Janine - and a guard are acting strange, and they suddenly sprout tendrils and try to attack them. Ackerson steals a pistol to kill the prisoner but doesn't have enough ammunition for the guard. Soren and Kwan arrive to rescue them, and as they make their way out of the facility they are attacked by more infectees. Kwan is seemingly cornered, but the infectees are suddenly restrained by a vision of the Mother, who reveals the identity of the parasitic aliens: The Flood. The Mother cryptically implies the Flood will try to coerce Kwan without infecting her, and is able to restrain them long enough for Kwan to escape and catch up with the others. Laera realizes she's been infected by the Flood and stays behind, apologizing to Soren for her previous outburst as she shuts the containment door. The others escape on Soren's ship.
The Arbiter's ship is drifting and caught in the Halo gravity well. Makee determines she no longer needs Cortana and smashes her data core as she and the Arbiter evacuate. Parangosky brings Halsey to the command center to try and reason with the Chief but when it's evident he's heading towards the Arbiter's ship to retrieve Cortana she merely gives advice on a good entry point. The Chief arrives and finds Cortana had uploaded herself to the ship's computer, and he manages to download her into his armor as the ship crashes on Halo.
Halsey communicates with Miranda who believes there is a contamination, and inside the command center several personnel start showing signs of the Flood's infection. Halsey manages to squeeze out of the room and put it on lockdown, while Parangosky is last seen jumped by the infected. She reaches Miranda and they discuss this infection, as Halsey realizes it's an entity that existed at the same time as the Forerunners. Miranda then realizes Halsey has been infected, and places her in a cryo-chamber hoping to find a cure, leaving them both sealed in her laboratory as the Flood surround it.
The SPARTAN-IIIs managed to get back to the main fleet, but Perez realizes Kai stayed on the corvette and she drives it into the Covenant assault carrier, destroying it and giving the UNSC much better odds. Chief recovers from the crash on Halo and converses with Cortana, who directs them to a nearby pillar. He confronts Makee and the Arbiter at the front door. In a pitched battle he manages to beat the Arbiter into submission, who accepts his death as penance for his shame.
In the distance, numerous other pillars start emerging from the horizon as well, while UNSC ships from the battle begin landing on Halo. Kai's motionless, yet whole body floats in the wreckage in space. The Chief follows Makee into the structure, but they are separated in the dark.
The voice he was conversing with is a floating machine sphere, a Forerunner Monitor, who mentions that something has awakened because he is there and flies off deeper into the facility.
Tropes:
- Adaptational Karma: Parangosky's canon counterpart got to retire comfortably after the end of the Human-Covenant War despite the horrific acts she committed. This version of the character is consumed by the Flood.
- Admiring the Abomination: Halsey, after getting caught right in the middle of a Flood outbreak and having seen a roomful of people die horrifically (and unbeknownst to her been infected herself), describes the parasite as "beautiful," seeing it as a connection with an ancient civilization, and utterly disregarding the horror unfolding around her. She's even shocked that Miranda wants to get the hell out rather than staying to learn everything possible.
- Anyone Can Die: The body count of major characters in this episode is immense. Kai seemingly dies in a Heroic Sacrifice, though the ending suggests she may still be alive, Laera is infected by the Flood and locks a door behind Soren, Kessler, Kwan, and Ackerson, and remains behind on Onyx, Parangosky is seemingly Devoured by the Horde (or likely simply infected by the Flood), and the Arbiter is slain in a duel with the Master Chief.
- Art Evolution: The Flood in the original games is high on the Body Horror, with characters mutating in front of you into a barely recognizable form with grotesque fungal bulbs and tentacles replacing their limbs. To portray this in live action would either be prohibitively costly CGI or an absurd number of practical monster puppets, so the show relies a little more on blue Tainted Veins, jerky movements, and more sedate uses of makeup for sweat and skin lesions, though specific individuals do display fungal mutations and explosive tentacle growths. This changes the aggressively infectious Flood in the games into something that needs just a little more time for the infection to take shape. While this is at odds with their depiction in the games it is fairly faithful to the greater lore as the initial victims are from Flood spores, whereas further mutations create Infection forms (the mobile fungal parasites seen in the games) which supercharge the assimilation and we are only a few hours into the outbreak.
- Asshole Victim: Parangosky finally pays the price for war when she's left by Halsey to die at the Flood's hands (though considering Halsey was infected after a tangle with one infectee, it's not as though Halsey could have saved her regardless). After what she pulled with Reach and the Spartans, she thoroughly deserved it.
- Badass Boast: Chief decides he is going to help the SPARTAN-IIIs and Parangosky objects.Parangosky: John, you can't save them.
Master Chief: You have no idea what I can do. - Big Damn Heroes:
- Kai and her SPARTAN-III squad are pinned down, Perez is injured, and their only option seems to be using the spike to obliterate the fleet. Then they hear fighting in the corridor, and see the Master Chief tearing his way through the Elites to rescue them.
- Ackerson of all characters, taking advantage of the currently motionless Flood infectee guarding his cell to snatch his gun and kill the Flood-infected Janine.
- Since Ackerson used up all his ammo killing the infected Janine, he's helpless to defend against the infected guard until Kwan and Soren arrive and gun him down.
- Bilingual Backfire: The Arbiter requests the Chief kill him to alleviate his shame, but assumes he doesn't speak the language and asks Makee to translate for him. She reluctantly comes around after trying to refuse, but Chief cuts her off and obliges anyway, saying "I know what he said" (it's left unclear whether he actually knows Sanghelli, just picked up context clues, or if Cortana is already providing the translation for him).
- Body Horror: The Flood infection starts by taking over the minds of the infected, before mutating their bodies with bulbous growths and tentacles.
- Bolivian Army Ending: For Miranda. After she seals the infected Halsey in a cryotube to halt the infection, she still has to deal with the issue of being trapped in a sealed lab surrounded by Flood-infected humans.
- Conscience Makes You Go Back: The Chief sets course for the Halo, but hearing the transmissions of Kai and the other Spartans facing impossible odds convinces him to rescue them, allowing Makee and the Arbiter to land on the Halo ahead of him.
- Conflict Killer: Once the Flood begins spreading, pretty much every conflict between the human factions is abandoned.
- Crucified Hero Shot: Piloting the Covenant Corvette to collide with the enemy cruiser requires Kai to stand with her arms stretched to both sides working the controls, resulting in a crucifixion pose.
- Death by Adaptation: Parangosky is still alive in the current Halo canon. Here, she seemingly dies (or is infected) at the hands of the Flood.
- Devoured by the Horde: The last we see of Parangosky, she's being held down by a half-dozen Flood infectees clawing at her in a sealed room.
- Disney Death: Makee crushes Cortana's storage unit with her heel, but Cortana predicted that outcome and transferred her program into the corvette's databanks to protect herself while pretending as if she's still vulnerable.
- Dissonant Serenity: The opening scene involves depicting the early stages of a Flood outbreak with one character violently stabbing another in the neck. This is done to a surprisingly cheery soundtrack.
- Dramatic Irony:
- Halsey admires the Flood due to believing they created the civilisation under Onyx. In reality, she's both Entertainingly Wrong and Right for the Wrong Reasons if the main canon still holds, where the Forerunners created that civilisation in both the main and Silver Timelines and the Flood were spawned from the remains of the Precursors.
- Miranda notes that the spore samples appear to be coming back to life and asks Janine what could cause that. She suggests light and temperature as options, but adds it could be in the presence of a food source...
- Epic Tracking Shot: the final Sword Fight between the Chief and the Arbiter is rendered primarily in long orbital tracking shots, broken occasionally by reaction shots of Makee.
- Eye Scream: One poor technician has a Flood parasite enter her body through her eye socket.
- "Facing the Bullets" One-Liner: Before ramming the Covenant corvette into the assault carrier, Kai remarks in Danger Deadpan "This is gonna hurt."
- Genre Shift: Much like Halo: Combat Evolved, the series takes a hard turn into a Zombie Apocalypse with Body Horror once the Flood show up.
- Heroic Sacrifice:
- Laera, having been infected by the Flood, seals the exit hatch behind Soren so he and her son will be safe outside.
- Kai stays behind on the captured Covenant corvette, and rams it into the enemy's lead flagship, turning the tide of the war at the cost of her own life.
- Heroic Second Wind: In a pitched fight, Chief is almost beaten into submission by the Arbiter, but just enough time is given with the Arbiter retrieving his sword for Chief to get back on his feet and use his grappleshot to throw the fight off balance.
- Hive Mind: It's evident the Flood are acting together at multiple times, coordinated in action and choices. Kwan's vision of the mystic returns and is able to freeze them in place for a moment just enough to let Kwan escape.
- Honor Before Reason: Chief has every reason to skip the space battle and make a run for Halo, but after being treated as a disposable pawn, he refuses to let the SPARTAN-IIIs be treated the same way, so he engages the Covenant corvette to help them evac.
- Human Popsicle: Miranda freezes Halsey in a cryo-pod in the hopes that her early-stage Flood infection can be reversed.
- I Am Not Left-Handed: When the Master Chief cuts through the Arbiter's chest armor on his left pectoral, the Arbiter simply transfers his energy sword to his right hand and keeps fighting.
- I Die Free: The Arbiter begs Chief to kill him so he can be free of the shame his title holds. Chief obliges.
- It Can Think: The Flood-infected Janine breaks and mutates her body to squeeze through the bars of her cell and infect others.
- It's Quiet… Too Quiet: Soren lampshades that getting into the base was far too easy after finding infected personnel standing motionless in the corridors.
- Last of Their Kind: When reunited with Chief, Kai notes that they are the only two Spartans left from their generation. Riz and some others are still technically out there, but since the former's retired, the two are clearly honoring her choice.
- Mercy Kill: After being left beaten and broken by the Chief, the Arbiter asks to be killed as a soldier who cannot fight is worthless and it's the only way to alleviate his shame. Makee begins to translate, but the Chief understands the intent and runs him through with an Energy Sword.
- Mythology Gag:
- The UNSC fleet arrives and Kai believes they have a chance at evacuation, but the closest ship is shredded by the Covenant assault carrier. The ship design is Halcyon-class, the same as the Pillar of Autumn from Halo: Combat Evolved.
- Chief slams his fist into the Covenant console and seems to download Cortana into his armor through his shielding. The original lore was that Chief's armor had a special liquid processor layer that allows him to carry an AI like Cortana in such a small space, before other works focused more on the data chip he puts in his helmet.
- Chief removes his helmet and holds it on his hip as he first surveys Halo. The image of the helmet on his hip with Halo in the background was one of the first promotional images for Halo Infinite.
- The Master Chief gets part of his chest armor scored in his fight with the Arbiter. His design in Halo 3 and Halo 4 included similar damage on his chest to indicate how long he had been fighting. The damage to his visor emanates both Halo 5: Guardians (scratch on left side) and Halo: Escalation (crack on right side).
- Perez gets shot in the side and her armor seal is compromised. Chief tells them to seal her suit and get out of there, which implies they have gear on them to do so. In Halo: The Fall of Reach in the first Spartan mission with MJOLNIR armor they boarded a Covenant ship and Samuel takes some damage to his armor that leaves it no longer air tight and they don't have equipment to patch it, so he remains on board to ensure the nuke destroys the ship and was the first Spartan lost in combat.
- Twofold for Kai. First, her Heroic Sacrifice has her ram a Covenant corvette into an assault carrier to destroy it and cripple the Covenant fleet, evoking Jorge and Carter from Halo: Reach. Her final fate, if she did indeed survive the collision, brings to mind Linda-058, the sniper in the main continuity who was wounded and placed in cryostasis but was abandoned in space before the Pillar of Autumn crash-landed on Halo, and Chief himself (no cryo) after destroying the Mantle's Approach in Halo 4.
- Master Chief survives a crash landing on Halo from high orbit. This is a recurring event in the franchise for various Spartan characters with Combat Evolved and 3 opening with him crashing into forests like a meteor, and high-altitude drops were common practice as depicted in the first season.
- Nice Job Breaking It, Hero: Halsey and Miranda unwittingly renewed the Flood threat when they brought the container up from the Forerunner city. In doing so, a biologist named Janine looks inside without thinking and gets infected, soon becoming Patient Zero of the subsequent zombie outbreak.
- No-Holds-Barred Beatdown: After his Heroic Second Wind, the Chief manages to wrestle the Arbiter to the ground, then pounds his face in until his helmet is knocked off and one of his mandibles is bent back.
- Nothing Is the Same Anymore: The Flood have been unleashed on the galaxy, claiming many lives including Parangosky and Laera, Halsey is put in cryo-stasis before her own infection can take hold, Kai commits a Heroic Sacrifice, the Arbiter dies at Chief's hands, and Master Chief and Makee are now in a race for control of the Halo - and the fate of the entire universe.
- Parrying Bullets: The Arbiter blocks the Chief's Magnum shots with his Energy Sword, though the unusual shape of the sword allows a few to get through and hit his armor. It mainly serves the purpose of protecting his unarmored face until he can close in to melee range.
- Patient Zero: Miranda was examining the spores found inside the Forerunner artifact and having a conversation with a lab tech Janine over containment procedures. Janine insists everything was fine but it's implied she didn't take it that seriously. She's shown freaking out and the infection is spreading. She's later seen in the brig, the infection getting worse, and she is the first to really contort and sprout tendrils.
- Ramming Always Works: Kai hijacks a Covenant corvette and rams it into their main assault carrier, wiping out their biggest asset and giving the UNSC fleet some breathing room.
- The Reveal:
- Kwan Ha is descended from a long line of protectors whose goal is to stop the Flood. The mysterious religious figure speaking to her is her ancestor who has minor control over them.
- The voice Chief is talking to in the Framing Device belongs to a Forerunner Monitor.
- Redemption Equals Death: In a roundabout way, Kai redeems herself for blindly following ONI's orders during their gaslighting of Silver Team and (unknowingly) leaving them to die on Reach. This time, she saves the remaining troops in her squad, and rams the stolen Covenant ship into their flagship to prevent millions of soldiers from dying.
- Redemption Equals Life: Ackerson was responsible for carrying out Parangosky's orders to leave Reach to the Covenant's mercy, and created the SPARTAN-III program as a means to create suicide troopers for the UNSC to dispose of at their leisure. His conscience over wanting to save their lives (plus a little threatening from Chief and the horrific realization that Parangosky intends to make him the scapegoat if she's exposed) results in him having a Heel Realization. Placed in prison, he unhesitatingly saves Laera and Kessler's life from a Flood infectee, resulting in Soren freeing him at Laera's urging. Unlike Parangosky, who is consumed by the Flood, Ackerson is able to escape.
- R-Rated Opening: The first season of the show could be surprisingly violent, but the second season had been a lot more restrained in comparison. This episode opens with someone getting violently stabbed in the neck by a pen, blood gushing everywhere. This was a warning that The Flood was going to get nasty.
- Save the Villain: Soren is understandably reluctant to save Ackerson, but hearing that he protected Laera and Kessler is enough to convince him the man deserves a chance.
- Sealed Evil in a Can: The device Miranda and Halsey recovered from the Forerunner lab was a spore sample. This sample manages to infect a lab assistant named Janine and spread across the base. Kwan quickly realizes these are the monsters she's been afraid of, and part of a Hive Mind called The Flood.
- Sequel Hook: Chief has landed on Halo, but so has Makee and they have both met the installation's Monitor. The nearby space battle appears to be sending a number of ships their way.
- Slow Transformation: Due to the Flood being unleashed through spores instead of curated Infection forms like the games, at least initially, the process of becoming a Flood is nowhere near as instantaneously horrific but instead a gradual thing. Infected people like Janine slowly slip into psychosis, the infection starts using them to produce simple parasites to infect others, before fully succumbing into a zombie-like state where the Flood begins mutating their bodies into rudimentary Combat Forms as the infection continues speeding up.
- Sword and Gun: The Master Chief starts his duel with the Arbiter using both his Magnum and his scavenged Energy Sword.
- Tainted Veins: Janine's veins turn blue as the Flood infection starts to take hold, just before she flips out and stabs a colleague in the throat with a pen.
- Too Dumb to Live: Janine, despite being a scientist, thought it would be a good idea to handle an alien artifact in a containment chamber that has unknown fungal lifeforms inside. Onyx is quickly turned into ground zero because of her foolishness.
- Uncertain Doom:
- Kai rams the main Covenant assault carrier in a move framed as a Heroic Sacrifice but she's later seen floating motionless in space. Given about the same time Chief crashes on Halo while inside a Covenant ship and survives, and Kai's right hand spasms briefly as she drifts in space, this leaves her fate open.
- While Halsey's infection is seemingly halted by locking her in a cryotube, Miranda is last seen facing down several Flood-infected humans with no immediate avenue of escape from her sealed lab.
- Vagueness Is Coming: The Monitor's conversation with Chief says that he expected his arrival, as he would only be here if It is awake and It is awake because he is here, and when Chief asks, he only gets an equally cryptic answer—but to those who know the games, it is clear that the Monitor is implying the Gravemind's existence and that the Flood have truly emerged from their ancient slumber.
- Wham Episode: The Flood debut, swiftly infecting the entire base on Onyx, resulting in Parangosky and Laera's deaths and Halsey's infection. Kwan, furthermore, is revealed to be part of a long line of Protectors against them by the vision of the Mother. Kai seemingly gives her life to cripple the Covenant fleet. The Master Chief reacquires Cortana at last and finally makes it to Halo in pursuit of Makee and the Arbiter, who he kills after a long duel. And in the final moments of the episode, a Forerunner Monitor - presumably this timeline's equivalent of 343 Guilty Spark - is shown conversing with the Master Chief.
- Wham Shot: The revelation in the final minutes of the episode who the Master Chief is talking to — a Forerunner Monitor like the one Kwan saw in her vision.
- Whole Episode Flashback: The episode starts with Chief in the dark, his helmet off and some scarring on his armor, talking with an oddly calm and melodic voice about what has happened recently. This set-up is returned to only a couple times, before the ending implies to have been a short Time Skip and Chief had encountered a Forerunner Monitor.
- Wrecked Weapon: The Master Chief's assault rifle is badly bent during the crash landing on Halo, forcing him to scavenge an Energy Sword and rely on it and his pistol during his duel with the Arbiter.
- Zombie Apocalypse: The Flood make their grand debut in this episode, and more than any other depiction, even the infamous Mona Lisa, resemble zombies here due to their more minimal mutations.
