Halo Alpha
Halo Alpha

This topic appears in the TV series. For information about the game version, see Catherine Halsey.

Dr. Catherine Elizabeth Halsey created the Spartan super soldiers. In recent times, this brilliant yet inscrutable mind has been more conflicted, likely about her creations.


Creating the Spartan Program[]

Dr. Halsey is a scientist with the UNSC. Her work to create the Spartan super soldiers has made her a critical member of the organization. She is also responsible for the inventions of numerous technological advances. Halsey was in a relationship with Jacob Keyes and they had a child together, Miranda Keyes.

She created the Spartan program for the United Nations Space Command to serve as a solution to what she viewed as a lack of evolution in humanity. She manufactured humans to be stronger, smarter, faster, and better than average humans.[1] For her creations to be superior, she had to begin their training at a young age, beginning recruitment at age six.[2] She traveled to different planets under the guise of starting a family with Jacob, and ultimately kidnapped these children from their homes[3] and replaced them with flash clones of themselves who later died.[4]

Halsey suppressed the children's memories of their lives before the UNSC intervened, effectively sealing away the memories of their families and loved ones.[1] The Spartan origin files were mysteriously "lost", as the children were deemed orphans who were adopted by the UNSC and became Spartans voluntarily.[5] Halsey knew that John-117 was exceptionally special and was sure to keep a close eye on him over the years.[3]

The Keystones and Cortana System[]

Halo 101 Halsey-Parangosky-Still

Halsey monitors her Spartans as they fight on Madrigal against Covenant forces. She watches Master Chief's video feed of him discovering an object in a cave. When he touches the artifact it activates, sending blue energy across the cave walls. Halsey watches in awe until Admiral Margaret Parangosky arrives in Halsey's lab. Parangosky cryptically reminds Halsey that her rebellious nature is nearing annoyance. Halsey wants the artifact to be taken back to her lab immediately upon arrival, though Parangosky notes that Miranda handles all Covenant objects. Halsey insists so Parangosky concedes. As she's leaving, she hears noises on the the other side of a door and peeks in. She the reprimands Halsey that her project has not been approved, as she was meant to cease all progress on clones. Dr. Halsey lies that she did pause the programming, but Parangosky sees through her lie and orders her to shut it down.

Halo 101 Miranda-Jacob-Halsey-Still

Halsey makes contact with John and learns he's been having visions when he touches the artifact, visions that feel like memories. She tells him to stay away from the artifact for now. When she ends communication, Adun vocalizes that he's not supposed to remember anything as she sealed them away. John later breaks protocol by ignoring a kill order against the sole Madrigal survivor, Kwan Ha. He disables the ships surveillance systems, causing a mass panic amongst the UNSC. Admiral Azmi demands answers from Halsey, as the worlds largest weapon shouldn't be misbehaving. Halsey explains that she thinks John is having memories, which shouldn't be possible. Azmi orders the marines on base to contain Master Chief when his ship lands. They watch as John seemingly removes his helmet and gives a gun to Kwan. Azmi takes this as an act of defiance and potential danger, instructing his marines to shoot the ship out of the sky if they have too. Halsey protests but he snaps that she's there as a courtesy and will be remanded to her lab.

Halsey secretly orders her Spartans to protect Master Chief and the artifact at all costs, even if it means firing upon the marines. This confuses Kai-125 at first, though Vannak-134 knows that friendlies wouldn't fire at the Chief. Their efforts are unneeded as Master Chief escapes from the base by using the artifact to repower his ship and fly into slipspace.[1]

In the day that follows, Halsey speaks with Fleet Admiral Hood about her plans for the artifact and Master Chief. They want the artifact because the Covenant wants it, which is good enough for them. Halsey has a plan to keep Master Chief in-check, though Hood doesn't want to know the specifics. Halsey tries to pitch the Cortana system to Parangosky, though she once again shuts Halsey down.

Halo 102 Jacob-Halsey-Still

She attends a meeting with other high-ranking officials, including Hood, Parangosky, and Halsey's ex-husband Captain Jacob Keyes. Hood isn't sure punishment for Master Chief is fit since he's a symbol of hope, a heroic statement, and a punishment would be bad for morale. Halsey undermines Admiral Parangosky by pitching the Cortana system to the council. She explains that it will overwrite Spartan consciousness and replace it with an artificial general intelligence. She believes it to be the next state in human evolution. The Spartans were the first step, while Cortana is the upgrade. Cortana represents the sum total of every available date point, holding the intelligence of the galaxy in her mind. She hopes to use Cortana to create Spartans who are more lethal, their judgement error-free, their performance upgradeable, and controllable. Captain Keyes reasons that Spartans such as John are people, but Halsey disagrees as he's much more than that. She thinks the Cortana system can help them win the war against the Covenant. Jenma points out that Halsey's previous theories depended on biological substrates derived from the illegal practice of human cloning. Halsey, however, has found a way around that. Parangosky reluctantly authorizes a trial of the Cortana system.

Halo 102 Halsey-Still

Master Chief turns on his beacon and allows himself to be arrested by the Spartans. He is taken through FLEETCOM where he watches Halsey drive off with the artifact. She takes it back to her lab where she admires it in its full glory. Chief, who is put into a holding cell for his actions, discusses the importance of the artifact with Halsey. He opens up about the emotions the artifact is bringing him, emotions he hasn't felt before, coupled with memories. Halsey assures him that she has a plan to fix everything. She returns to her lab where she removes the barrier around her clone, making the being open her eyes.[6]

Halsey's clone is now awake and aware that Halsey created it to obtain vital organs from herself without harming her true body. Halsey collected samples of her tissues and used them to create the clone. The clone retains emotions, thoughts, memories, and feelings that Halsey had during the time the tissues were initially taken. It has no active memories beyond her point of inception, as it did not inherit Halsey's new memories or thoughts. It inquires about the children used in the Spartan programming, learning that 35 survived the original augmentation, meaning more than half died. As it compiles the Sorvad solids before it, the clone deduces that Halsey is after its brain. Halsey explains that she has perfected the method of real-time neuroelectrical imaging, meaning the Cortana system is viable and can be integrated into a working Spartan. They catch up on John and how the Cortana system will help him out of this current predicament. The clone asks about Miranda, their daughter, but Halsey ignores this question. The clone reminds Halsey of when she was its age and the uncertainty she felt about killing a living breathing version of herself and asks what has changed since then. Halsey admits that progress has changed things.

Adun and Halsey work together to activate a scanner that digitizes the clone's facial features, then holds open the eyelids while a needle pierces the eyeball. When the neural substrate acquisition is complete, the clone has died, and they use another machine to implant the needed mechanisms and information into John's mind. Adun destroys the clone in a tub of acid that effectively disintegrates the body. While John remains in stasis, Halsey calls Cortana who appears before Dr. Halsey.

Halo 103 Halsey-Still2

As they are acquainted with one another, Halsey explains that she's going to run some tests on the artifact John found on Madrigal to determine its provenance and functionality. Cortana changes the subject - her neural implant is working perfectly, but she can't take full operational control of the subject. Halsey has limited her access to the reticular formation, which upsets Cortana, as that goes against her directive. Halsey recommends she use John's downtime to familiarize herself with the trove of human knowledge available to her. Cortana reveals that it will only take her 7.6 minutes out of the hour given. Halsey assures Cortana that she'll be kept very busy.

Halo 103 MC-Halsey-Still2

When John awakens, he has little interest in meeting Cortana or interacting with her. He does, however, comment on her resemblance to Halsey. Cortana states that it's nice of him to say, as her features were made to feel familiar with her voice and accent designed to be pleasant. She contains a hollow particle elixir that allows her to appear in an environment. Cortana views this as a partnership, while John wants to command her. She is coolly dismissed by Halsey. John doesn't approve of the new partner but Halsey is certain it is a great leap forward for everyone.

She then runs more tests on John with the artifact, and he reluctantly makes contact again. He is flooded with more jumbled memories as Halsey and her assistant Adun marvel at the physical impact the artifact has on John. Cortana shuts John down to access control of the object, which inadvertently ceases John's connection to it, and it becomes inactive. Halsey stays apprised to John's activities through Cortana, who reports to her throughout the day. Cortana contacts Halsey to warn her that John is removing his emotion regulator. Halsey wants Cortana to help him so he'll see her as an ally and not a spy. Cortana reluctantly agrees and helps John remove the pellet. This spurs John to explore Reach without his pellet, then he decides to contact the artifact without the pellet so he can properly experience the visions.

He returns to the testing bay and demands Cortana open the door, which Halsey allows her to do. Halsey visits John later while he's speaking with Cortana about his parents, a conversation that stops when she arrives. He tells her of his latest antics and she feigns surprise over his regulator being removed, his second contact, and discovery of his home planet Eridanus II. She offers to fly drones over the planet to explore it, but he insists to going on an exploration mission. Halsey decides to join him and brings Adun along. As Adun and Halsey privately discuss the dangers of John's memories, Halsey admits that if John remembers too much, that Cortana was created for just that reason.[2]

Halo 104 Master-Chief-Halsey-Still

John, Halsey, and Adun arrive on Eridanus II where they locate John's childhood home. They begin to excavate the burial of the case. John thinks the keystone might be within the case, but it's only dozens of repetitive sketches instead. Halsey suggests returning to Reach to examine the sketches and catalog them, but John is already heading for his former home. He asks Cortana to recreate what his home looked like before its destruction. The longer she projects the images the more his memories begin to return. He physically interacts with his younger self as he watches memories unfold before him, his actions causing curiosity from Halsey. Cortana explains that she stopped the projection so whatever John is seeing, he's seeing by himself. He sees Halsey playing a game with him as a boy at the counter while his parents watched. He then remembers the cave in which he discovered the larger keystone for the first time. He is suddenly stricken with the knowledge of where it is, and hurries off to find it. Halsey and Adun follow him outside the Reach For Life installment to a cave. John and Halsey marvel at the large keystone encased in a boulder.[3]

Exile From the Program[]

The UNSC rallies to excavate the object, which is not only encased in a boulder, but sealed behind a crystal substrate. Master Chief confides in Keyes about his memories of Halsey visiting him as a child, something that Keyes promises to look into. Keyes tells Halsey and Parangosky about the revelations. Parangosky wants to cease all the operations including the Spartan protocols by bringing everyone back to Reach immediately, with the artifact. She wants to terminate Master Chief. Halsey admits they could but leverages the fact Parangosky knew the true origins of the Spartan program. She kept all the files and will release them if Parangosky doesn't keep the program going. The woman concedes angrily. Keyes wants Miranda removed from the artifact studies to keep her hands clean. Halsey quips this is the only parenting issue they can agree on.

When Adun ruptures the substrate containing the keystone, it emits an energy blast followed by a high frequency sound that cripples everyone in the vicinity. Master Chief touches the larger artifact and remembers being kidnapped by Halsey and replaced by a clone. When he breaks connection, Halsey arrives and sees his anger. She offers to explain but he's overcome with anger. He angrily lunges at her so she commands Cortana to shut him down. He falls to the ground in a limp state of unconsciousness. Halsey retreats to her ship for her safety and refuses to let Cortana tell John her location.

Halo 105 Halsey-Still

Suddenly, slipspace is breached by the Covenant and a viscous fight ensues, with Halsey demanding that the Spartans bring the artifact to her. They struggle to reach her ship so she redirects them to Miranda's ship, which explodes in fire, forcing her to redirect them to herself again, despite the dangers. Master Chief witnesses Kai in danger and diverts from the plan despite Halsey's screaming orders to keep with the plan. Master Chief tries to fight the brute but is knocked across the field. The artifact is ultimately stolen by the Covenant.[5]

The survivors of the battle return to Reach. Once the ship is empty except for himself and Halsey, John seals her inside the UV decontamination room. Cortana tries to understand why he's acting out, initially believing it to be a result of the artifact. John clarifies that he's never felt better. He activates the decompression chamber which will release a high dose of radiation that will burn and liquidate Halsey. Cortana pleads with John to release her while Halsey screams out for him, the clock ticking down. John demands that Cortana take control of his body and force him to open the door, otherwise her creator dies. Cortana doesn't have that ability as she can only overload his neuro pathways to place him in a temporary stasis. He doesn't believe her. The clock runs down and the radiation begins, so John saves Halsey before slamming the door shut. He needed to test the limits of Halsey's AI system but doesn't play to save her from what's next.

Halsey is questioned by a representative from the Judge Advocate General. Parangosky and Keyes watch in secret, with her admitting to Keyes that she's made Halsey the scapegoat for the entire operation. The general has been instructed to limit his questions to cloning. John interrupts the meeting and makes the general leave. He asks why she did it. Nothing she says will make sense until the benefits manifest. She's accepted that he will hate her. She was planning the future of their species since natural evolution is failing them since humans are still hardwired for conflict and selfishness. If they were going to survive they needed a force that would intervene and prevent conflict before it started. She created the Spartans to protect humanity from itself. He wants to skip to the part where she kidnapped them. She needed children, no older than six, so their training and augmentation could be carried out properly. They were too young to volunteer and parents don't give up their children very easily. The thing she replaced him with was a genetically compromised clone that began exhibiting signs of illness before passing away. It allowed the parents to properly grieve the loss of their child and give them closure. She views this as a reasonable, a statement he throws back at her. She lied to them for years while they fought and killed for her. She corrects that it wasn't for her.

Any challenge to the status quo is always thought to be mad until people see the benefits. He asks who knew about the truth so she covers up for her partners by saying everyone looked the other way. She thinks it was worth it to unlock the mystery's of the artifact. They have upended everything she thought she knew about their place in the universe. He's the key to unlocking more secrets. He has a confection to the thing they're calling the Halo. She knows he will take them there to lead their species beyond its current limitations. He needs her to do it and ensure their sacrifices aren't in vain. He plans to finish what they started without her.

Halo 106 Halsey-Still

Halsey meets with Parangosky and is a little annoyed after being interviewed by the representative. Parangosky reveals that she needed a scapegoat and so did the council, so they chose Halsey. She doesn't' believe her at first but Parangosky reveals her plan to send Halsey to a new lab on the Burial Mounds, away from the UNSC base. It will frame her as the reason for the failing Spartan program and give Master Chief a bit of justice. The Spartan program and Cortana will be transferred to Miranda, who is finally getting the promotion she deserves now that Halsey isn't holding her back. Halsey tries to use her blackmail but knows it will only land them both in jail, which isn't good for either of them. Parangosky calls for two MPs to escort Halsey back to her quarters where she will begin packing for her next day departure.

As she packs, Adun visits ready for his next order now that his mission is complete. They can't access Cortana as she's been black boxed, something he is partially responsible for as he solidified the UNSC's firewalls and database. Halsey thinks Cortana will find her way back now that she's alone and untrusted by John. Cortana won't just give up because of Adun's systems.

Halo 106 Halsey-Still2

Miranda gets Halsey's message to come see her, so she obliges. Miranda sees through Halsey's manipulations of a goodbye tea. Halsey relents that Miranda can't conduct studies on the artifact without her. Miranda lashes out over her mothers attempts at concern. Halsey tries to appeal as a scientist, but Miranda retorts that she kidnapped, mutilated, and murdered dozens of children. Even if it was to save billions others, she tried to save humanity at the cost of her own. Halsey apologizes for letting her daughter live with such anger for so long. She doesn't believe in the concept of family but should have explained herself to her daughter when she was old enough. It was never her intention to hurt Miranda, becoming emotional over the admittance. She's had enough emotional baring and walks across the room. Miranda leaves shortly after, unaware the entire thing was a rouse for Halsey and Adun to obtain Miranda's biometric identity via a contact lens.

By evening, Cortana has broken through the UNSC's restrictions, systems, and fixed Adun's system. She reveals that John is about to touch the artifact again, offering to place him in stasis, but Halsey refuses as she needs to see this happen. She shows Halsey both John and Makee's vitals during the connection and they learn how the pair are inexplicably linked during contact.[4] Halsey and Adun prepare for the next stage of their plan with help from Cortana. Cortana reluctantly shares that John and Makee haven taken their relationship to a physical stage, being closer than ever. As such, Halsey successfully accesses Makee's entertainment systems when the refugee is alone.

She wants to talk about John, a person she knows better than anyone. She's raised him since he was six. She knows they are fond of each other which makes her happy. John is in great danger, they both are, as the artifacts must never be delivered to the UNSC. Makee rebuttals that John thinks they are safe in humans control, so Halsey asks if she has the same opinion after living among them. Halsey loves humanity but views humans as being the problem as they're stuck. They're venal, selfish creatures who create misery and pain wherever they go. She knows humans will use the artifacts as weapons to destroy themselves. Makee doesn't think John would let that happen. Halsey presses that John does not exist and hasn't for many years, as only Master Chief is there as a product of the species who made him. Their gifts are to previous for either side, so they must control the Halo with Halsey's help. She thinks John will listen to Makee. They are cut off by a visiting guard who heard voices. When he leaves, Halsey reappears to ask her to convince John to remove the artifact and bring it to her where she'll be waiting. They can tap into the intelligence of the Halo to unleash the trios full and true potential as a species. Makee realizes Halsey wants to become like a god just as the Covenant and has heard enough.

Halo 106 Adun-Halsey-Still

When Makee turns her down, Halsey invokes "Zed Protocol". She tells the Spartan members of Silver Team that the UNSC cannot be trusted. Kai questions the orders so Halsey instructs the other Spartans to eliminate her so they tie her up. Cortana becomes increasingly uncomfortable with the situation as Master Chief is walking into a trap set by Riz and Vannak. Cortana's discomfort increases when Halsey reveals that she doesn't need John as Makee can activate the artifacts. Cortana can finally fulfill his creation place to place John in stasis and completely take over his body. She believes that Cortana, operating through Master Chief, will be the very best of everyone. Cortana, disagreeing with the ethics of the plan, betrays Halsey to warn John of the trap. She cuts the ships connection to the FLEETCOM base. She leaves Halsey and Adun stuck on their plane without a method of escaping Reach. Halsey is in awe of her AI developing empathy and emotional connections. Adun frantically suggests they leave without the Spartans, but Halsey refuses. A blast from the keystone renders all technology obsolete.[7]

Military troops are ordered to shoot down Halsey's ship to keep it from leaving the tarmac. Adun and Halsey struggle to get the ship online, with Halsey then delaying their departure until the Spartans arrive with the artifact. Adun convinces her to abandon them as they can live to fight another day. As they prepare to leave, the troops open fire but it isn't enough to subdue the ship. Kai, infuriated at the idea of her escaping, runs at inhuman speeds, leaps into the air, lands on Halsey's ship, and proceeds to shoot the engine with her gun. She breaches the cockpit. Adun tries to close the door to block Kai from entering, but she grabs the closing doors and pries them open with a shout. She removes her helmet and turns to Halsey, demanding to know her real name.

Halsey assures her that her name is Kai-125, but the Spartan wants to know the name her parents gave her. She wants to know who she is - Halsey admits she's exactly who she was meant to be. Adun strikes Kai over the head, which only angers her. She grabs Adun by the throat and slams him through the ceiling, killing him. Halsey flees into an escape pod while Kai bangs on the door separating them. Halsey escapes, leaving Kai in the failing ship.

Later in the day, Halsey is running from a group marines in a field. They arrest her and take her back to FLEETCOM, where Miranda and Jacob watch her be escorted to the cells. Miranda enters the interrogation room where a silent Halsey is waiting. Miranda updates her mother on the outcome of her actions. She's already been tried by a private military tribunal and found guilty of treason, kidnapping, and a myriad of other crimes. Though, her guilt was never in question, just her punishment. The UNSC has deemed her to dangerous for exile or imprisonment, a sentiment that Miranda can barely believe. In an ironic twist of fate, an Article 72 has been issued against Halsey. She subject to execution first thing the next day, something Miranda requested to tell her. Halsey thought by keeping Miranda from the Spartans and past mistakes that she was protecting her, but it had the opposite effect by hardening her. She needs to stop chasing a ghost and let go of it, for her sake. After an interlude of silence, Miranda says goodbye to her mother.

Later, Halsey begins to seize and medics attempt to save her life as her body shakes, her nose bleeds, and she is visibly dying. Miranda is initially overcome with emotion over her mother dying, but then remembers Halsey's descriptions of the flash clones dying. She pushes past the medics to scream at the clone where she is, but gets no response. The medics assure Miranda they will try to save Halsey, and Miranda relays that the thing on the table isn't her mother. The clone flat lines, leaving the real Dr. Catherine Halsey the UNSC's most wanted fugitive.

The real Halsey is on Reach, in the city of Manassas, writing in her journal about the future of humanity. She contemplates how humans are born, live, and die by the rules of blind evolution. They are not equipped to survive what comes next. It's time to take control of human evolution, to discover true humanity, which the Halo will provide the key for. As she's escorted to a ship that will take her her off Reach, Halsey concludes that much has been lost and more sacrifices are to come. But they will rewrite what it means to be human, achieving transcendence.[8]


HALO 202 Julia-Halsey Still

Halsey is taken captive by the ONI and held in a room powered by AI. She receives daily visits from the clone of a young girl named Julia, whom Halsey tries to illicit information from. The clone expires each time before Halsey can learn more about the man holding her. Eventually, James Ackerson makes his presence known as the man keeping her captive. Halsey inquires about John and Cortana but Ackerson merely introduces her to her new attendant - another clone of Julia.[9]

Ackerson visits Halsey to say his peace about the Spartans, as well as, goodbye. She won't be there to see it but the things she made will become the foundation of something extraordinary. He hopes that gives her comfort in the end. Halsey asks if he wants to know how his sister Julia died. This surprises him, though he doesn't falter long. She remembers all of them, but especially his sister. She was curious and had so many questions. Halsey never knew who would make it through the augmentation and who wouldn't. Julia didn't survive it. Halsey told her a version of what Ackerson just told her about being a small step forward. Julia couldn't understand. Halsey knows Julia loved Ackerson very much. She hopes that gives him some comfort. He leaves Halsey alone for a moment before bringing Soren into the room so they can be reacquainted before the end.[10]

Halsey's reunion with Soren is cut short by the Covenant attacks on Reach, which short-circuit the illusion keeping them prisoner. She can navigate them out of the cells, forcing Soren to trust her even though he doesn't want too. As she talks about his past and the accident with his arm where she let him go, Soren accuses her of rewriting history. He escaped her, and she supposes his story is just as good as any. Halsey leads them to where Cortana is being kept, though the AI is stolen by Makee. When Halsey is injured by a blast, Soren questions what she meant by letting him gone. She saw his potential and how everyone looked to him. After his augmentation failed she need John to look to himself. That's why there was no one guarding the ships the night he ran away. They eventually reach FLEETCOM where Halsey has an awkward reunion with Keyes and learns Miranda is off-planet. She goes with him to a civilian transport that is leaving the planet. The civilians are all aboard the hangar but the fuel lines are still connected. Keyes exits the plan to disconnect them. He ensures Perez can fly the ship before he does. Keyes runs to disconnect the fuel lines when a Jackal sniffs him out. Perez watches the forces surround Keyes. Halsey, who isn't onboard yet, wants to help Keyes, but Soren knows they can't. Keyes tells Perez to leave him. Halsey screams for Jacob as Soren pulls her away. Perez takes a deep breath and pushes the engine into takeoff. Keyes removes the fuel connector from the base so the hangar fills with fuel. He puts a pipe to his mouth and asks for light. The hangar explodes in fire just as Perez enters the sky.

Halsey screams in the hall just as John, Riz, and Vannak arrive. She collapses in sobs after her husbands death. She goes to the edge of the building that overlooks the burning planet. Another round of attacks hits FLEETCOM as forces breach the room, kicking off another battle. John squares off with the ARbiter and picks up an energy sword. He's hit with a plasma round and the Arbiter almost impales him until Makee gives the order to stop. Vannak tries to save John from the Arbiter and is impaled with one of the darts. It explodes in his chest, killing him. John screams at the death of his friend. He tries to crawl to Vannak but is too injured. Soren grabs his shirt and drags him away while Riz watches. Vannak's corpse stares at a hole in the ceiling where the sun is peaking out. A bird circles the area while chirping.[11]

The survivors are rescued by Soren's wife Laera and Kwan Ha, but not before Riz suffers substantial injuries.[12]


Halsey is a passionate scientist who is obsessed with "improving" humankind. According to Jacob her obsession has cost her every personal relationship she's ever had. Once Halsey's sets her mind to something she will cross any legal as well as moral line to accomplish it (creating then murdering her clone, kidnapping children, manipulating her daughter)

Behind the scenes[]