In a flashback to 22 years ago, a young John-117 sneaks out of the barracks at the UNSC's SPARTAN-II training facility, hopping the fence to meet fellow trainee Soren-066. The two made plans to desert together, but John has had second thoughts. A tense standoff ensues as John attempts to dissuade Soren at gunpoint, but ultimately, he lets his brother-in-arms go free.
In the present day, the Master Chief and Kwan Ha travel to an off-the-grid asteroid colony known as the Rubble, the place he and Soren had planned to escape to. The two reunite, and John learns that Soren more or less runs the colony now, having settled down with a wife and child. At his home, Soren presses John about his desertion, urging him to have his emotion-inhibiting implants removed and stop making excuses for Dr. Halsey's horrific "treatments", but the Chief remains adamant that it was all necessary.
Back on Reach, FLEETCOM reconvenes. Captain Keyes reports that Vinsher Grath has been installed as Governor of Madrigal and the planet is again under UNSC control, but has concerns about his methods - reports indicate he has begun executing insurrectionist sympathizers in the streets. The Admirals dismiss these concerns as irrelevant to the war effort, however, and discussion turns to the Master Chief's desertion. Dr. Halsey continues to defend John and the SPARTAN-II program, and takes the opportunity to pitch a project that she claims could prevent such issues in the future: an Artificial Intelligence she calls "Cortana".
Halsey's pitch is alluring: she claims that Cortana will not only enhance the mental faculties of the Spartans above that of normal humans, but allow the UNSC to remotely override their free will in case of emergency. Of course, creating such an AI will require human neural tissue harvested from illegal flash-clones, but Halsey's never been one to let the law stop her. Fleet Admiral Terrence Hood is impressed and authorizes the development of the project, much to the chagrin of ADM. Parangosky, who had previously ordered it shut down.
The next day, John asks Soren for help understanding the artifact he recovered from Madrigal, which doesn't seem to respond to anyone else's touch. Soren leads him to a crazed mystic who was abducted by the Covenant and lived to tell the tale. The mystic reveals that these ancient devices, known as "Keystones", are central to the Covenant's religion, and that John is one of the few beings capable of activating them. Furthermore, these Keystones are but guides to an even greater and more terrible artifact: the "sacred ring", a weapon that could end life as we know it.
On High Charity, the mobile capital city of the Covenant, the young woman seen in the previous episode, Makee, stands alongside the High Prophets to hear the reports from Madrigal. Upon confirmation that the artifact John activated was, in fact, a Keystone, Makee requests permission from the Prophets to infiltrate the UNSC and retrieve it, but is denied — her ability to activate the Keystones makes her a "Blessed One", an integral part of both their religion and their plans for humanity, and she cannot be risked in such a way.
Desperate to stop the Covenant from finding this mysterious "ring" and with few options open to him, John decides to leave Kwan with Soren and return the Keystone to the UNSC, turning himself in for desertion. In his cell, Halsey questions him about his motives for both his desertion and his return, and John confesses that he feels she's the only person he can truly trust. She reassures him he made the right choice... right before thawing out one of the flash-clones she'll use to make Cortana.
Tropes:
- Asteroid Thicket: The appropriately-named Rubble is located in a large asteroid in the center of a vast and thick asteroid field.
- Body Horror: Soren's left arm was horribly mangled during training, with the flesh misshapen, a finger missing, and a giant gash showing the subdermal armor beneath.
- Blatant Lies: Halsey is asked if she's found a way to create a general artificial intelligence other than via illegal human flash-cloning. Halsey just nods to avoid getting a verbal denial on record, since we know from the previous episode she's kept her illegal project going despite Admiral Parangosky's orders.
- Crossing the Burnt Bridge: Upon learning that the Keystone leads to a weapon even more powerful than what the Covenant is already capable of, John sees no choice but to return to the UNSC and Halsey to warn them of the threat, seeing the latter as the only person he can trust.
- Delusions of Eloquence: Vinsher executes prisoners with a nice rhyme, Punctuated! For! Emphasis! with a Boom, Headshot!. Then he sees a camera drone recording this and shoots it as well.
- Every Scar Has a Story: Makee is shown to have scars on her back while undressing. The story of how she got them is revealed in the following episode.
- Emotion Suppression: The Spartans are given hormone suppressants that deaden their emotions, administered through a implant in their back. Soren has since removed his, and it's implied the Keystone disrupted John's.
- Expospeak Gag: Kwan admires the beauty of them traveling through slipspace. When the Chief tries to explain what's happening via the usual Layman's Terms metaphor, Kwan just tells him to shut up so she can enjoy the moment.
- Fanservice: Makee stripping off her Covenant garb, revealing there's nothing underneath, including a generous long shot showing her nude from behind.
- Flashback: To 22 years ago, during John's time in the Spartan training program. He tries to stop Soren-066 from deserting, but ultimately lets him go.
- Jurisdiction Friction: Miranda complains to Admiral Parangosky about Dr. Halsey being given first crack at the artifact, even though alien technology is supposed to be her department. Parangosky brushes her off, as she's already in a bad mood after Dr. Halsey went over her head to get Cortana approved, and is in no position to start undermining Dr. Halsey now that she's been forced to go along with her plans.
- Mad Oracle: Reth is a mystic who was held prisoner by the Covenant to see if he can activate their artifacts, which he couldn't. It's not clear if his imprisonment or his visions were what drove him insane, but he keeps himself in willing confinement with other such mystics.
- Mercy Lead: John gives Soren a five-minute head start before alerting the camp about his desertion. Unfortunately, Soren needed ten minutes, and we learn that lacking the extra five minutes caused him considerable extra trouble in his escape.
- No OSHA Compliance: Doctor Halsey and Admiral Hood have a private meeting on a large open balcony, high up on a high-rise, with no railings to speak of. That said, neither person ventures very near to the edge either.
- Oh, Crap!: John is understandably horrified when he learns that the Keystone leads to a weapon. If weapons mighty enough to glass a planet are insignificant compared to the power of the ring, the UNSC must be warned.
- Price on Their Head: Kwan has a bounty on her, not from the UNSC but Vinsher, who wants to eliminate any potential threat to his reign.
- The Reveal:
- The artifact is a Keystone, one of several that can be used to track down the Halos.
- "Blessed One" is a title the Covenant use for humans that can activate Forerunner technology.
- The titular Halo sought by the Covenant is confirmed to be a superweapon that would turn the tide of war.
- Tyrant Takes the Helm: Vinsher is put in charge of Madrigal as a UNSC puppet. He promptly starts executing Insurrectionist sympathizers.
- What the Hell Are You?: Reth starts screaming "What are you?" when John shows that—unlike himself—he can activate the Keystone.
