Three weeks have passed since Discovery rejoined the Federation. The ship has been repaired and updated.
Saru updates and reports to Vance's team. Vance hands out assignments to various captains. When Saru offers to fulfill these missions, Vance insists Discovery stay close as his "rapid-responder" explaining to the other captains that Discovery's unique instantaneous travel drive must remain top secret.
Vance wants Discovery to be ready to respond to problems on the planet Argeth which seems to be under threat by the Emerald Chain.
The Discovery crew are introduced to their new tech and devices. The ship is hailed by someone outside the Federation distortion field and when put on screen, they see Book's cat, Grudge.
The ship carries a message from Book, recorded three weeks' previously, wherein he tells Burnham that he has gone in search of a black box for her investigation into The Burn.
Burnham wants to go to rescue Book and get the black box. Saru insists the ship stand ready as per Vance's orders.
Burnham goes to Georgiou with the intention of disobeying Saru's orders. Georgiou joins up.
While discussing Burnham's love life, Georgiou has another episode where she is struck by disturbing flashbacks of blood and explosions. She appears to find her son killed.
They approach the salvage planet, Hanhow, where Book was headed. An Orion makes contact and warns them off. Georgiou intimidates him into letting them land.
Tilly finds Grudge in her room and discovers Book's ship and Burnham are no longer with Discovery.
Posing as salvage buyers and using Grudge's cat collar tracker, Burnham and Georgiou look for Book among Osyraa's slaves.
They find him just as a Bajoran slave tries to steal a water ration. The Orion sends him running to the perimeter and when he crosses over, his neck marker explodes, taking his head off.
Adira works alone with Gray asking why she isn't making an effort to make friends.
Stamets comes in and Adira shows him how she's improved the spore drive.
Georgiou distracts the Orion and Burnham and Book discuss how to get him out.
Saru approaches Tilly about Burnham. Tilly advises that he must tell the Admiral before the Admiral finds out from some other source.
Burnham and Georgiou trigger a distraction while Book and Rin rally the slaves.
Saru reports Burnham's unauthorized absence to Vance who informs him that things are heating up with the Emerald Chain.
While the Orion and his goons are aboard Book's ship to get the dilithium, the transport ship arrives and the slaves escape the facility but must wait for the perimeter fence to come down.
Georgiou and Burnham fight the Orion and one of his men. Georgiou defeats her guy but is incapacitated by another flashback. She recovers in time to help Burnham and get the controller to turn off the perimeter fence.
Book and Rim direct the other slaves to a transport ship but Rin blocks a shot meant for Book and Book won't leave him behind. They are beamed aboard Book's ship and return to the Federation with Burnham and Georgiou.
Georgiou fires on the Emerald Chain ships hovering nearby, sending them crashing into the salvage facility.
Book gives Burnham the black box he acquired.
Burnham confronts Georgiou about her flashback episodes and realizes that Georgiou doesn't know what's happening to her.
Stamets sees Adira talking to Gray and asks her about it. They bond over their love of dead people. Adira offers to help repair Stamets' arms by removing the stents.
Burnham and Book board the turbolift for Burnham to go to meet Saru and Vance. Book apologizes for putting her in this position. He pauses the turbolift and they are about to kiss when Linus appears transports in and then out again. Book kisses Burnham.
Culber and Stamets discuss Adira.
Vance addresses Saru and Burnham about her rogue mission. He leaves the consequences up to Saru. Saru demotes Burnham from First Officer to Chief Science Officer and Burnham agrees that it is the right decision. He leaves and she removes her badge.