In USS Discovery‘s sickbay, Philippa Georgiou tells Dr. Hugh Culber that in the Terran Empire, the Emperor‘s physicians were buried with the dead sovereign, to inspire loyalty. Georgiou rebuffs Culber’s questions about her blackouts, but he warns her that the slow onset of brain dysfunction will eventually leave her mad. Georgiou relents, and Culber scans her in the presence of Commander Michael Burnham. Her heart rate is elevated, though Georgiou deflects and says it is caused by rage.
In the corridor, Burnham runs into Cleveland Booker, who says he must return to his home planet, Kwejian. His brother Kyheem passed along the request via the courier network; the planet is threatened by Osyraa and the Emerald Chain, with whom Kyheem has been dealing for fifteen years without previously asking for Booker’s help. Booker asks Burnham to accompany him, but she notes the planet is a two-week journey at warp and that a transwarp tunnel would more likely than not kill them. They will need help, she says.
In Admiral Charles Vance‘s office, Booker explains that The Burn caused damage to subspace that shifted Kwejian’s moon’s orbit, which in turn caused tidal changes. Sea locusts emerged from the ocean and consumed their harvest, leaving millions to starve. The Emerald Chain provided them with a repellent to push the locusts back into the sea, saving their harvests – but the Kwejian had to hand over their trance worms in exchange. Booker does not know why Osyraa has returned. Vance is unsurprised and explains that the Chain often contacts pre-warp civilizations in distress, something it has done to at least fifty other star systems being tracked by Starfleet. Such civilizations typically collapse. Vance says he is unwilling to risk sending Discovery, but Saru suggests travelling to the planet with the legal status of observers; the presence of the Federation’s watchful eye might temper Osyraa. Vance consents, but tells Saru to take a defensive posture and jump away if there is any danger.
At the ruins of the salvage facility on Hunhau, Osyraa chastises Tolor for losing the Andorian Ryn, who escaped to Discovery with Booker and Burnham. Osyraa tells Tolor that when she took him in as a child, she had complicated feelings about the death of his father, implying she killed him to retain control of the mercantile exchanges. Suddenly, she beams him into a holding cage with a trance worm that quickly mesmerizes and then eats him. Back in orbit, Osyraa’s sizable vessel, the Viridian, jumps to warp.
In a corridor, Saru and acting first officer Sylvia Tilly discuss ship’s business – Booker and Burnham are preparing for the jump to Kwejian, Ryn has recovered and asked to speak with Saru, and Linus has been confined to quarters until his annual shed is complete. Saru also asks about the search for his signature order, which Tilly says has been narrowed to “execute,” “hit it,” and “manifest.” Nobody likes “manifest,” Tilly admits, and Saru notes Captain Christopher Pike had used “hit it,” leaving him to mull the options.
In engineering, Paul Stamets and Adira Tal brief Saru and Tilly on their analysis of the SB-19 data and information from the black boxes gathered by Burnham. The data show that The Burn started in the Verubin Nebula. They have also discovered a deliberate audio signal coming from the center of the nebula. The signal has been distorted by magnetic interference, but when played aloud, Tilly recognizes it as the song hummed by the Barzan family aboard the USS Tikhov. Adira also reveals that Gray Tal used to play the tune on his cello because Senna Tal‘s parents had sung it as a lullaby when he was a boy. They modify the signal to filter out the distortion and are surprised to hear a Federation distress signal. Adira will write an algorithm to determine whether it includes an encoded message. It will only take a few hours because “she’s pretty fast,” Stamets notes before Saru and Tilly leave. Once alone, Adira asks Stamets to instead use the pronouns “they” and “them” as they have “never felt like a ‘she’ or a ‘her’.” Adira reveals they have never told anyone that except for Gray.
Dressed in civilian clothes, Burnham and Booker head to the bridge. Booker reveals that Kyheem is not his biological brother but that they use the term because it is “something we said, we felt.” They drifted apart after Kyheem began hunting trance worms for the Chain. Burnham asks if he can fix their relationship, but he says the starving Kwejian is his priority. Booker says he regrets that she will not see Kwejian at its prior height of beauty, but Burnham says she will like it anyway.
On the bridge, Joann Owosekun notes that Keyla Detmer has modified the helm station’s interface from the programmable matter version from the Starfleet upgrade. Detmer says she needs a fail-safe. With Discovery ready to jump, Saru orders the crew to “execute,” leaving the bridge officers underwhelmed. Above Kwejian, Discovery receives no response to its hails as Booker observes nervously. Owosekun reports that a cruiser class ship will arrive in thirty minutes and Booker says it is likely Osyraa aboard the Viridian. Saru sends Booker and Burnham to the surface, instructing Burnham to figure out if Discovery can be of service but to return to the ship at the first sign of trouble.
In sickbay, Georgiou complains about having to dress in a tight white outfit that makes her look like a “Human spermatozoa,” but Dr. Pollard explains it is made of a hyperconductive material that interacts with electromagnetic gel for an extensive medical scan. Pollard anesthetizes Georgiou and begins the scan.
In a room with a piano, Adira plays the cello as Stamets enters. They explain the skill came with the Tal Trill symbiont. They also reveal that they can still feel the manifestation of Gray but that he has stopped talking to them. Stamets speculates that Gray needs space and Adira says the symbiont’s memories from past lives often leave them confused. Stamets says the algorithm will take hours to finish and he plays the piano as Adira follows on their cello.
In Saru’s ready room, Ryn bursts in angrily demanding an audience, but Tilly confidently castigates him.
The still-irritated Ryn thanks them for healing him but says that Federation assistance “always comes with strings.” He asks to beam down to Kwejian with Booker, and Saru says he can if the Kwejian accept him but warns that Osyraa will arrive in fifteen minutes and most likely would recapture him. Just then, Booker and Burnham enter Kwejian’s defended areas and Discovery loses track of their signal.
In a forested area on the planet, Burnham notes that her tricorder readings are scrambled and Booker welcomes her to the Sanctuary. Around them float the blue sea locusts; Booker notes that their presence so far inland means the planet has not received any repellant for weeks. Book uses his empathic abilities to part the locusts so they can pass, telling Burnham that he cannot force them aside and instead can only ask. Kwejian scientists have long sought a way to ask the locusts back out to sea, to no avail. The two are suddenly surrounded by armed Kwejian. The leader complains that Booker, whom he calls Tareckx, brought the Federation with him. The two verbally spar, and Booker reveals that the man is his brother Kyheem.
While still undergoing the scan, the sweat-dampened but semi-conscious Georgiou’s encephalographic readings peak and Culber warns that she is having another episode. The scan is only eighty-three percent complete, but Pollard warns she could have a cerebral hemorrhage and the scan should be aborted. Culber insists, saying they cannot otherwise learn what is wrong with Georgiou. The disturbed doctors watch in shock as Georgiou’s face distorts briefly but bizarrely. Georgiou has another flashback to her discovery of the bloody San in the Terran universe and awakens. She leaves angrily, having stolen one of the electrodes used for the scan.
On Kwejian, Booker criticizes the character of Kyheem and their family for selling trance worms to the Chain. Kyheem reveals Osyraa lured Booker to Kwejian in order to recover Ryn. The Kwejian desperately need the repellant, but Booker refuses to return Ryn to slavery.
The Viridian arrives and scans Discovery. Gen Rhys suggests going to yellow alert, but Saru says diplomatic protocol cautions against any action that could be misinterpreted as provocation. Saru tells R.A. Bryce to try to break through to Burnham and have her return to the ship before accepting Osyraa’s hail. Saru says Discovery is an “observational presence” there at the request of the Kwejian. Osyraa says they are harbouring a “wanted criminal,” Ryn, though Saru says he is unaware of Ryn being wanted by any authority recognized by the Federation. Unbowed, Osyraa tells Saru to send Ryn to her ship, or the Kwejian and the away team will pay but Saru resists. On the planet, Booker and Kyheem nearly come to blows over giving up Ryn.
Saru questions how Osyraa can claim to hold Ryn in slavery when Orions were once enslaved themselves. She responds that her ancestors “knew that power is virtue and that there is no nobility in suffering.” She notes that the Federation does not want a conflict with the Chain and warns Saru that if he does not give up Ryn in five minutes, she will destroy the planet’s surface. Saru orders Tilly to bring Ryn to the bridge.
As he drinks Kwejian whiskey, Kyheem talks to a holographic projection of Osyraa, who notes that the Sanctuary has a strong defense system. He insists he brought Booker to the planet as Osyraa wanted, but she says she needs to capture Booker and Burnham to leverage. He refuses to turn off the defense system and hand them over, so Osyraa instead threatens to allow the locusts to eat Kwejian’s harvest, noting he has a young son who would starve. When he does not give in, the Viridian opens fire on the planet, threatening to burn ten hecapates of forest for every minute he delays. With the defence system holding for now, Booker and Burnham flee.
On Discovery, the crew question why Osyraa wants Ryn badly enough to carpet bomb Kwejian, but he refuses to say. Saru orders weapons brought online, saying they must prevent Osyraa from committing atrocities.
At a corridor computer terminal, Georgiou hacks into the electrode, but is distracted when Discovery goes to red alert, concerned about Burnham. She is intercepted by two guards and Culber, who reveals he knows she was going to help Burnham but that her condition makes her a liability. She tells Culber the scan shows she is dying, but he says her situation is “not that cut and dry.”
On the surface, Burnham and Booker run through the forest as weapons fire begins to penetrate the Sanctuary’s defense system, though they are still unable to contact Discovery. Rhys cannot determine if the Viridian‘s shields have any weaknesses, but Ryn volunteers to show them, citing his experience on salvage duty. Nilsson warns that Discovery attacking Osyraa will draw retribution from the Chain against the whole Federation. However, Tilly suggests firing on her from a non-Federation ship – Booker’s ship – piloted by a “Starfleet pilot who will be disciplined severely for disobeying orders and for going rogue.” Detmer shares a knowing look with Saru.
Detmer and Ryn leave the shuttlebay in Booker’s ship. He directs her to fire where the Viridian‘s gunwale meets the aft nacelles. Amid intense fire, Detmer says she cannot determine from sensors whether she hit her target, but Ryn assures her that she has weakened Osyraa’s shields and must continue the attack. Ryn is alarmed when Grudge jumps into his lap, but Detmer reassures him the cat is harmless.
From the surface, the Viridian is close enough that Booker can identify his ship attacking with the naked eye. They are surrounded by Kyheem’s guards, but all are knocked to the ground by a nearby explosion, and Booker and Burnham fight them off. Booker’s ship’s shields are down to ten percent, prompting Ryn to suggest retreat, but Detmer says they must continue until Burnham is clear. Ryn tells her that he fears being vaporized by Osyraa, but she tells him that “if you face something, you can beat it.” Detmer switches to full manual control. On the planet, Kyheem attacks Booker, who says he must have known all along that Osyraa would consider kidnapping him for leverage. He gives a weapon to Kyheem and dares him to hand him over.
Kyheem is unable to betray his brother. They watch from the surface as Detmer continues aggressively attacking the Viridian. Ryn tells her how to target the weapons system generator. Significantly damaged, the Viridian stands down. Osyraa promises retaliation for their actions and warps away. On the surface, Kyheem says they will starve without the repellant. There are too many locusts for Booker and Kyheem to move them out to sea, but Burnham has an idea. She returns to Discovery and prepares to amplify the electromagnetic connections between the locusts so that the brothers can use their empathic powers. Booker and Kyheem begin chanting together as their foreheads glow. The surrounding locusts swarm, and Bryce amplifies the message. The locusts begin moving back out to sea, saving the Kwejian harvest and preventing mass starvation.
In the mess hall, Detmer gushes about her piloting adventure to Owosekun, Nilsson, Rhys, and Bryce. Ryn sits alone nearby, where Tilly joins him. He warns that Osyraa will return with a vengeance and says he was raised to believe that the Federation was deceitful. He also warns that Osyraa wants him so badly because he knows a secret: that Osyraa and the Chain are running out of dilithium.
Booker, Burnham, Kyheem, and Kyheem’s son Leto walk past Linus in the corridor, much to Leto’s delight. Booker says that Kwejian is still his home but that he can make a difference for many planets aboard Discovery. Burnham takes Leto away with a promise to go peel skin off of Linus’s face. Kyheem says the name “Book” sounds odd, though Booker promises that there is a story behind it that he might share the next time they meet, hopefully sooner than in another fifteen years. Booker tells Kyheem he held things together and saved Kwejian, and they touch foreheads before parting.
In engineering, Culber finds Stamets and a sleeping Adira “burning the midnight oil.” They have nothing to do until the algorithm finishes, and Culber urges Stamets to let Adira sleep as they talk softly. Stamets tells Culber that the manifestation of Gray has stopped speaking to Adira but that their work remains excellent. Adira reveals they are awake and, tired, leaves. Culber amusedly notes that Stamets feels pride.
Burnham and Booker prepare to repair his ship, which was hit by eight photon torpedoes during the battle. She asks if he meant it when he said he understood their mission. Booker replies that Discovery saved them from a century-long problem and that he wants to similarly help more worlds. She says he will have to clarify his intentions with Saru and says she liked seeing Kwejian; Booker replies that he liked being there with her.