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Captain Burnham and the USS Discovery race to stop Book and Ruon Tarka from launching a rogue plan that could inadvertently endanger the galaxy.



Aboard Booker's ship, hidden in the husk of the dead world, Booker and Tarka carefully place the isolynium within the core of the isolytic weapon. Booker remarks on the small amount of the substance, but Tarka reminds him the Federation banned it for a good reason, as "a little goes a long way". Tarka estimates the weapon will be ready within five to six hours, after he calibrates it to destroy the DMA's controller while protecting its internal power source. Booker urges him to speed it up; Tarka assures him that Burnham and all the others will understand once it was over, and that no one else would be lost to the DMA.

Aboard the USS Discovery, Saru enters Burnham's quarters, where the captain informs him she has received a message from Booker, encrypted so it could not be traced, and thought he should see it. As Burnham plays the message, Booker tells her he has looked over all the data on the DMA, including the fact that it was probably a mining device rather than a weapon. However, Booker remains adamant that it must be destroyed before it claims any more lives. He tells Burnham that he does love her, but cannot see any middle ground, and bids her goodbye. Burnham had hoped telling him about the DMA's true nature would change his mind, but if Booker and Tarka were not stopped, there was no telling what would come next. Saru agrees that Booker has left them no choice.

Nhan 3190 Federation Security uniform

Commander Nhan, Federation Security

At Federation Headquarters, Fleet Admiral Vance remarks that saying the matter was not easy would be "an insult to understatement", noting the optics and the complexities involved. Burnham asks Vance if she is capable of leading this mission, and Vance asks in return if that was what she wanted. She replies that it is. Vance informs her that while President Rillak has her own views on the matter, she is also aware that Discovery is the only ship capable of reaching Booker in time to stop him, and that no one knew Booker better than Burnham did. Vance also reminded the President that Burnham has never let him down. However, Vance warns Burnham that Rillak is concerned that if the mission does not go smoothly, Burnham could be too emotionally compromised to be involved, and the admiral shares that concern. Therefore, he is sending another officer along with Discovery, someone who would be able to step in and give the necessary orders, backed by Vance's full authority. Burnham protests that this was Saru's job, but Vance points out that Saru is also close to Booker. Vance is aware of the awkward situation, but tells her that the officer is a "friendly face", and asks them to join the conversation. Burnham is pleasantly surprised to see it is Commander Nhan, now working for Federation Security. Though aware of their prior history, Vance believes that as a Barzan, devoted to duty, Nhan would be ideal. He leaves the two alone to catch up. Nhan starts by saying she had only met Booker in passing, but believed him to be a good man, and apologizes that things had come to where they were. Burnham asks about her new Security posting, as she believed she had returned to Barzan II with the USS Tikhov. After connecting to her distant family "didn't work out", Nhan took a security posting (and also upgraded her breather to be less intrusive), leading a cleanup task force against what remained of the Emerald Chain, a covert posting she couldn't tell anyone about. Burnham had seen the reports of the bloody fighting. While it was not the way Nhan would have preferred to return, she thought it best if it were her rather than a stranger, and Burnham is glad to have her.

In his quarters on Discovery, Saru contacts President T'Rina, asking her for a favor. On Ni'Var, he had joined her in a thresh-tor kashek meditation, and found it greatly eased his troubled mind; he asked to do so again. T'Rina agrees, and they kneel down on the cushions Saru has produced on the floor. However, even through the holographic communication, T'Rina can see that Saru has difficulty focusing. Saru admits he is distracted, particularly by the anxiety surrounding the hunt for Booker and Tarka, but T'Rina sees that is not all. He mentions that Su'Kal is worried about the DMA, and Saru does not know how to comfort him, but thinks that personal feelings are "of little import" in such dire times. T'Rina, however, believes that such feelings were always of import. She suggests that, if formal meditation does not help, engaging in the peaceful routines of daily life help to re-establish inner balance, perhaps a walk or a shared meal between friends, and offers to join him. Saru, somewhat surprised, says he will consider it, and thanks her.

Saru heads to the bridge to prepare the ship for departure, as the crew discuss the mission. Lieutenant Commander Nilsson notes that Booker did not give them much of a choice, while Lieutenant Commander Rhys argues that there were a number of people who believed that he and Tarka were doing the right thing. Saru firmly shuts down the argument, saying no matter their opinions, they had their orders. Just then, Burnham and Nhan enter the bridge, the crew looking pleased to see her. Nhan tells them she is glad to be back, but to feel free to ignore her as she was just observing. Burnham, however, believes they should know the real reason why she was there – because Burnham was so closely connected to Booker, Nhan would ensure they completed the mission, and adds that she would have done the same thing in Vance's place. It was not an easy mission, she acknowledges, but it was critical they succeed. She instructs Lieutenant Commander Owosekun to place their destination on screen: the uninhabited rogue planet where Booker's ship was hiding. They had the element of surprise, and could not waste it; if Booker's ship used the spore drive to jump into the DMA before they could detain them, pursuit would be far more dangerous. Burnham orders black alert and the cloaking device engaged, giving the command with a half-hearted "Let's fly".

Act One[]

Discovery arrives in view of the rogue planet; Booker's ship is inside a cavity, four thousand meters below the surface, and Rhys is detecting no scanners or other defenses. Burnham orders Lieutenant Commander Detmer to bring them in as close as possible. Detmer brings the ship into position and then comes to a full stop, and Booker's ship is brought on screen. Burnham asks Saru and Nhan to meet with her in her ready room, and to have Dr. Culber join them.

In her ready room, Burnham explains that Booker's ship has a built-in security disruption field, so they could not transport directly on board, but they could bring a cloaked shuttlecraft to a maintenance hatch on the aft side of the ship. Nhan respectfully suggests that Burnham should not be leading the mission, and Burnham assures her she had not planned to; Saru would take point, along with Dr. Culber and Lieutenant Commander Rhys, and Lieutenant Commander Bryce would pilot. Nhan points out the work Bryce is doing with Dr. Kovich for the first contact, but Burnham is again on top of it, saying that Zora will continue to look for communication frequencies able to pass through the galactic barrier, leaving Bryce plenty to analyze when he returns from the mission. She then turns the floor over to Saru, who explains that they will use a multi-phasic signal discriminator to override the external proximity sensors and gain entrance before Booker or Tarka are alerted. Once they reached the bridge, Dr. Culber would attempt to de-escalate the situation so that they could take control of the ship. Culber sees that Booker is acting out of anger and grief, believing he was doing what was right, but was not unreasonable; Tarka, however, was the "wild card". They will all have their phasers, set to stun, to be used only when the situation requires it. Burnham is confident he will make the right call, and admonishes them to be safe.

As the cloaked shuttle leaves Discovery, Bryce and Rhys argue about Booker's motives; Bryce believes Booker will be imprisoned for life because he stole classified tech and is helping make an isolytic weapon, but Rhys believes Booker is acting so rashly because the Federation is not acting quickly enough, adding that Bryce didn't know what it was like to lose everything. As they become more heated, Saru intercedes, firmly telling them they were there to execute their orders, regardless of their feelings about their mission or one another. Culber takes a more conciliatory approach, saying that while they all had different opinions of what Booker was doing, they were all there to fix it, and they would do so together. Saru thanks the doctor, before ordering Rhys and Bryce to prepare the ship for docking. Bryce reports back to Discovery that they were at full stop near the hatch and engaging the airlock field. Burnham orders Owosekun to isolate the shuttle's cloaking field, so that they could see what was going on. Owosekun confirms the shuttle has soft-docked, and there was no sign that Booker's proximity sensors had picked it up. Burnham orders Saru to proceed, but suddenly an alarm goes off; programmable matter begins enveloping the shuttle, disabling its cloaking device.

On his ship, Booker is surprised to hear an alarm he doesn't recognize, and Tarka explains it was an intrusion alert system he developed on the way to Porathia. Booker is incensed that Tarka didn't tell him, but Tarka reminds him they were on their way to buy illegal weapons tech on the black market. Booker recognizes the intruder as one of Discovery's shuttles, and realizes Burnham put a tracker on the isolynium. On Discovery, Nhan asks if Burnham knew Booker's ship could do that, but the captain is just as surprised as she is, and orders Owosekun to beam them out. However, Owosekun can't get a lock on them due to the disruption field from Booker's ship. With no choice, Burnham orders Saru to abort. Saru orders Bryce to get them out, but Bryce is unable to break free. Booker panics, demanding Tarka shut down the defense system before it killed them, but Tarka had programmed the system to be autonomous; they would be dead before he could remove the first layer. As the shuttle's structural integrity begins to fail, Tarka suggests running an EMP charge through the hull, which could slow it down enough for the shuttle to escape. Booker runs the charge, and tells the shuttle to fire maximum thrusters. Owosekun is just able to beam them back to the ship before the shuttle is torn completely in half.

After seeing they were all well, Burnham orders the shuttle crew to return to stations. Owosekun reports that the tracker signal has just disappeared, because Booker had found it. Opening a channel, Booker asks if the crew made it back alright, before saying that he had a job to do. His ship then disappears; it has jumped, and Nhan believes they were going for the DMA. "Then so are we," Burnham says. Although they had no idea where the controller was, they had to follow; they could not allow the first contact with Unknown Species 10-C to be an act of aggression. Burnham again orders black alert.

Act Two[]

Discovery arrives within the DMA. Burnham orders shields raised, and to find the controller before Booker and Tarka did. Nhan asks what would happen if they beat Booker's ship to it; Burnham admits figuring that out was next on her list. Lieutenant JG Linus reports dark matter interference was greater than expected; Owosekun confirms, saying that cloaking will be spotty, and it was already impacting shield stability as well as scanner range; Detmer is reminded of her grandmother's saying about "finding a needle in a haystack". Saru believes Booker will have similar problems, but Nhan points out that he has a head start. Burnham sets her people to work, telling Detmer to plot out a grid search pattern, and Owosekun to scan for the rift around the controller, which would be easier to find than the device itself. Nhan then asks to speak privately with Burnham and Saru; Burnham turns the conn over to Nilsson, and heads into the ready room.

Once alone, Nhan reveals that she had been ordered to allow the operation to go without interference, but in case they failed, she was ordered to brief them on a vulnerability that would allow them to disable Booker's ship: the prototype spore drive. If they fired a photon torpedo into the impulse manifold, it would set off a chain reaction which would destroy the spore drive… and the entire ship along with it. That would not allow them to beam anyone off the ship, which is why Nhan emphasizes it was intended as a last resort. Saru is concerned that the explosion will set off the isolytic weapon and destroy Discovery along with Booker's ship, but Nhan believes they will survive if they jump away first. Nhan is apologetic about Booker and knows the options aren't pleasant, but Burnham interrupts, saying it was not just about Booker or even Discovery; the Federation needed the spore drive to break its dilithium dependency, and there had to be a way to save it. Nhan reminds Burnham that she had the authority to relieve Burnham of command, and Burnham heatedly replies she did not intend to give up command of her ship while she was seeking a solution. Saru intercedes, bringing up advice Dr. Culber had given earlier that in times of division, they identify things they could agree on, a shared goal leading to compromise. Burnham suddenly has an idea, and calls down to Commander Stamets in engineering, who was trying to increase the scanner range. She tells him to put Reno on the scanners, and runs an idea by him: they know the DMA is mining for boronite, and it wouldn't leave until the boronite in the area was exhausted. Stamets catches on: if they scanned for the remaining boronite in the subsector, they could calculate the rate of consumption and predict when the DMA would jump again, but he warns about the margin of error. Burnham tells him to work with Zora; if they could get a timetable, they could convince Booker to stand down. Nhan suggests bringing it up to Admiral Vance; Burnham adds they should do it together.

Aboard his ship, Booker is still searching for the controller, and the interference is already affecting his ship's cloak. He is angry about what happened to the shuttle; though apologetic at first, Tarka bluntly tells him that he has worked for the past ten years to achieve his goal, and with Discovery in the way, there will come a point where Booker will need to choose between them or stopping the DMA. Booker tells him not to go behind his back again, and to finish the weapon. Tarka tells him it is finished, and asked him five minutes earlier where to load it, but he was too distracted. Booker curtly tells him to load it in torpedo tube six, and returns to scanning for the controller. Suddenly, his ship almost flies directly into the cloaked Discovery, forcing them to turn hard to port. Burnham orders sensor-blinding bursts to be sent out to dampen Booker's scanners so he couldn't find the controller.

Tarka is annoyed to see Discovery has found them again, and reports scanner capacity has been reduced to 40%. Booker fires a magnesium charge into a nearby hydrogen cloud, a trick Burnham recognizes as one they used to evade pirates in Breen space. She orders Detmer to take the ship towards the cloud; Saru warns that with shields compromised, the heat blast will short out the thermal regulators. Burnham assures him they will avoid the blast if they dive in low, and Booker's sensors should be blinded enough for them to escape. The charge goes off, and Discovery is able to dive out of the blast radius. Burnham then has Detmer take them into a nearby dark matter cloud, and from there resume the grid search. She then calls engineering, asking for the timetable, but Stamets is still working on it. Booker, observing the blast, correctly guesses Discovery has gone into the dark matter cloud to escape it, remarking on how well he knew Burnham and her crew. Tarka believes perhaps he knew them too well, to which Booker tells him to get back to work on the scanners.

Owosekun detects particles from the galactic barrier, indicating the presence of the rift, and are quickly able to spot the DMA controller. Nilsson remarks on how the 10-C didn't seem to care, how their device churned space and took boronite, before moving on. Burnham is determined that they will stop the DMA, but do so the right way. Nhan reminds her that Booker will be on his way to do it his way, and Burnham replies they would be ready, before ordering Detmer to take them in closer. She intends to put Discovery between the controller and Booker's ship, and to hold the line as long as possible.

Act Three[]

Burnham again asks Stamets for the timetable, and he responds he is working on it with Zora, just needing a little more time. Nhan is blunt, saying they can't keep playing cat-and-mouse with Booker forever, and points out that new data had not swayed him before; why does Burnham believe it would now? Burnham firmly believes Booker is reasonable and logical, and would not want to see people hurt. Nhan then asks what they would do if she was wrong; Burnham believes there would be another way, but Nhan points out there was another way. She passes a tactical program over to Rhys, one that he recognizes would destroy Booker's ship. Burnham is adamant that this is a last resort. Nhan hopes to avoid that option, but she was under orders to prevent Booker and Tarka from firing on the controller. Owosekun then reports sensors were picking up Booker's ship, moving fast. Burnham knows he would need to decloak for a target lock, and orders Owosekun to keep theirs active for as long as possible until she gave the order to drop it, then tells Stamets to let Zora take over the timetable work, as he would be needed for a spore jump.

Aboard Booker's ship, Tarka admires the genius of the DMA controller, and believes their plan would work. The weapon is loaded, and ready to fire on Booker's mark. Just then, Discovery jumps in front of them, blocking the shot. Booker can't beam it in without lowering the disruption field, and that would allow Discovery to beam them out. Tarka tells Booker to use the spore drive, but Discovery matches him, staying between him and the controller. Tarka scolds him for not firing when he had a lock, but Booker retorts that they had one weapon and he didn't want to waste it. He locks onto Discovery's shields and opens fire, bringing them down to 50%. Burnham knows Booker is not trying to hurt them, but Nhan dismisses the semantics, believing they could both agree that Booker was firing on them. Burnham reluctantly orders return fire, matching Booker's intent to warn them off. As Tarka tries to justify himself again, Booker cuts him off, saying that he was trying to find a home in another universe, while Booker had lost his home in this universe. Booker jumps again, but Discovery matches his move. Tarka, having had enough, slams his fists on the weapons controls and fires a full spread of quantum torpedoes. Burnham remains convinced Booker is not behind that attack, but Nhan heatedly tells her that she lost half her team on her last mission waiting too long to make a call that should have been made sooner, and did not intend to make that mistake again. As Burnham pointed out, the stakes were too high; they had to destroy Booker's ship to stop him. Burnham turns to Saru, who reluctantly concurs. As she is preparing to give the order, Stamets calls in, saying that he has an estimate: Approximately 154 hours, or a full week, before the DMA collects all the boronite in the area and jumps again. Burnham, relieved, orders Lieutenant Christopher to hail Booker's ship, but Christopher reports no response. Telling him to keep trying, Burnham turns to Rhys, telling him to obey the order to destroy Booker's ship if Nhan gives it. She then leaves Saru the conn, and tells Nhan to follow her to her ready room.

Once they were alone, Burnham asks Nhan how many people her team was able to save; Nhan replies they saved 115. Burnham remarks she had made a decision not long ago that saved lives, but lost others as well. As leaders, they saw only success or failure, right or wrong, but she points out that nothing was ever that binary; there was a middle ground, and she was convinced she could get Booker to see it. Nhan half-jokingly asks if she planned to put on an EV suit and knock on his viewscreen; Burnham replies she would use a shuttle and fly in front of his viewscreen. Nhan warns that she will give the order to fire if they try to launch the weapon, and that would also kill Burnham in the process. Burnham, however, continues to believe in Booker, but knows Nhan will save her ship and crew if she's wrong. Nhan wishes her luck.

Act Four[]

As Burnham's shuttle leaves Discovery, Booker threatens to take Tarka's hands off if he touches his console again; Tarka remains fixated on his obsession with stopping the DMA. Just then, he sees the shuttle approaching and hails it, ordering it to identify. Burnham does so, commenting on how he had not answered their hails; Booker replies he had been "a little busy", and both compliment their maneuvering. Burnham pleads with him to stop, and reminds him he had wanted a middle ground… and now she had one. She transmits the data on the timetable, noting that the DMA would continue collecting boronite in that uninhabited space for at least another week; while it's there, no lives were in danger. She offers them a solution that both President Rillak and Admiral Vance approved: they would come aboard Discovery and remain there for that one week, so that the Federation could use that time to make contact with Species 10-C and work to convince them to withdraw the DMA. If that failed, they would back the plan to destroy the DMA controller. Booker enables the privacy settings and turns to Tarka, who protests against taking the deal. Booker retorts that he lost "voting rights" when he fired the torpedo spread at Discovery. Booker believes it to be a viable compromise, while Tarka thinks it was a lie, an effort by Burnham to convince him to back down. Booker, however, trusts Burnham completely. Tarka pleads with him to let him take the power source so he can go home, but Booker brings down the privacy screen and agrees to Burnham's proposal. Burnham relays the good news to Discovery, and orders the shuttlebay to prep for Booker's ship.

As Burnham returns to Discovery, Tarka asks if Booker was familiar with the concept of "expected utility"; he explains it was a concept of game theory, a mathematical method to help determine the optimal move in a situation where risk was high, and the outcome was unclear. "Such analysis can lead to unexpected solutions," he concludes. "Of course, one has to be clear-headed to make the right move." Tarka brings up the controls for the weapon, and when Booker asks what he's doing, he replies, "I'm being clear-headed." Booker tries to stop him, but it is too late.

Just as Burnham beams back to the bridge, Owosekun reports that the disruption field on Booker's ship has lowered, and they were reading a transporter signature and a massive tachyon surge inside the DMA controller. Booker hails Discovery, warning them that Tarka beamed the weapon into the DMA controller and urges them to escape. Burnham asks if they could stop it, but Saru does not believe they can. Tarka urges Booker to escape, as the detonation would cover half a parsec and the null-space bubble around the weapon will protect the power source, not their ship; Booker refuses to leave until Discovery is safely away. As the weapon is about to detonate, Burnham angrily orders black alert and Discovery jumps away. Book's ship does the same a moment later, and a massive explosion envelops the area. Now safe, Tarka assures Booker that it had to be done, and now they could both get what they wanted: the DMA was gone, and Tarka could use the power source to go home. But when he scans for the power source, Tarka is horrified to realize it's not there… it was being powered from the other side of the wormhole, outside of the galaxy.

Aboard Discovery, now back at Federation Headquarters, Burnham is visited by Nhan, who asks about Booker; Burnham has tried hailing, but he is not responding. With no idea how Species 10-C would respond, Admiral Vance is initiating emergency protocols in case of retaliation, and the first contact mission is being fast-tracked. Bryce was still working on communicating through the galactic barrier, and Discovery would leave the following day. Nhan has already said her goodbyes to the crew, promising not to be a stranger; Burnham jokingly adds she would hold her to that. Nhan thinks to what Burnham said about how things were not always black and white, and mentions she did find her family on Barzan, living in a single village. She visited a park, seeing children playing and their parents hovering, as her own had done. But she found there was so much she couldn't tell them, like being from 932 years in the past for instance, so she decided not to stay; it was the same about not telling the Discovery crew that she was back in uniform, describing herself as "all or nothing". But after this mission, she remarks on being "okay" with finding middle ground. Burnham assures Nhan there would always be a place for her on Discovery, and both wish each other well on their upcoming missions.

In sickbay, Dr. Culber is alone, shutting down some of the equipment, when Saru enters. The doctor remarks on the long day, and asks how Saru was holding up; Saru admits he was doing as well as expected. He thanks Culber for his calm during the mission, only wishing they had been successful. Saru asks for Culber's advice on how to deal with an "overture", as he calls it, from T'Rina, admitting to feeling silly about it given what they had gone through; T'Rina has asked him to dine with her, and he is trying to convey the best way of declining the proposition, even if he had the time for it. Culber looks amused as Saru explains about how he and T'Rina are from vastly different cultures, and how he was already committed to his work with Starfleet and on the Kaminar High Council. Culber asks him straight if he had feelings for her, and Saru admits that he does. Culber respectfully (and somewhat jokingly) says that in his professional opinion, Saru was "being an idiot", noting that while connection was always a risk, given everything that was going on, it was something Saru could handle. Just then, Lieutenant Christopher calls Saru to the bridge. Saru thanks the doctor for his "unexpected candor", and leaves.

As Saru arrives on the bridge, Burnham shows a live feed from the USS Mitchell at the last location of the DMA… showing that a new DMA has appeared in its place. Whether they wished it or not, they had just made first contact with Species 10-C.

Background information[]


  • The title "Rubicon" was noted in the Star Trek: Discovery Season 4 Loglines on 14 February 2022. [1]
  • The title may derive from the phrase "crossing the Rubicon," which means crossing a point of no return.



  • TRR: "Rubicon" discusses the making of, and events in, this episode.

Links and references[]



Guest starring[]


Uncredited co-stars[]


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Star Trek: Discovery
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