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"Cibola Burn" is the tenth and final episode of the fourth season of The Expanse. Overall, it is the forty-sixth episode. It dropped on December 13, 2019 as part of Amazon Prime streaming's full-season release strategy with season 4.


Ashford closes in on an enemy while uncovering a dangerous plot. Avasarala faces a crossroads in her personal and political life. The Roci crew works to reestablish life on Ilus in the wake of a deadly catastrophe.


Back online[]

Dr. Elvi Okoye falls through the inside of the orb, and as she falls she sees visions of strange orange and brown light, and rapidly moving eel-like beings made of energy surround her. Before she has hit the ground, the lights and patterns that were activating all over Ilus begin to fade out.

Dr. Okoye falls to the ground, unconscious, next to the lifeless robotic body of The Investigator. Holden rushes to help her, dragging her away from the orb as she wakes up again in a panic. Holden asks her if she's alright as she gasps for air in shock, and she replies that she doesn't know. They sit together at the edge of the wall, and Dr. Okoye notes that The Investigator is gone.

On the Rocinante, Alex, Naomi and Lucia see on their monitors that all the energy emissions from the planet and from its moons have completely stopped. Naomi successfully restarts the reactor, causing all three of them to celebrate, and they get notifications that the other ships in orbit have also managed to get their power back. Alex sends a message to the Edward Israel, informing them that he has target-locked their drive cone and that they need to have a serious conversation.

Holden finds a wounded and unconscious Amos, with his head against Chandra's dead body. He shakily reaches out his hand, but is surprised and relieved when Amos wakes up with a start. He asks Amos how bad it is, and he replies that he's "a little messed up". Holden helps Amos get up so they can get out of there.[3]

The tether is cut[]

The Roci and the Barbapiccola untether from each other, and the two crews celebrate that they managed to save the Belters' hard earned lithium. Felcia promises to bring the Earthers responsible to justice, and Lucia sadly replies that she also has things to answer for.[4]

Putting hate aside is talk[]

In the Tynan, Klaes Ashford is flying through an abandoned asteroid mine in his hunt for Marco Inaros, noting that someone has been working there recently as the equipment is relatively new. One of Ashford's crew points out that they would have nothing to mine here for money, as the rocks there are only iron-nickel. They find a suspicious ship in the navigation logs that turned off its transponder upon arrival and back on after leaving, and Ashford decides to go after it.

Ashford interrupts one of his men who is torturing a Martian prisoner. Ashford apologizes to the prisoner, who is an MCRN officer, as he was not supposed to be tortured, and interrogates him further. The prisoner helped Inaros attack Earth for money, and Ashford realizes he has also been selling weapons to Inaros's faction by stealing them from Mars. He tries to reason with the prisoner, stating that Marco is smart and brave but also incredibly naive in thinking that violence is the only way to get what he wants, and that by helping Marco enact his violence, the prisoner is putting everyone in danger. Ashford believes the Ring Worlds are a chance for humanity to change and get a new beginning, but the prisoner is unconvinced and uncooperative, insisting he doesn't know where Marco is. When Ashford leaves, the prisoner spots the pliers that were used to torture him earlier, floating unattended around the room.[5]

Comparing notes[]

On Mars, Bobbie is following Beltran around, when she is stopped by Leelee and a couple of Esai Martin's thugs, causing her to lose sight of her surveillance target. Though Leelee is hostile and wants Bobbie to stay away, Bobbie realizes they are both distrustful of Beltran and were both following him. After a tense verbal exchange which ends with Bobbie threatening to beat the three of them again, Leelee offers that they can compare notes instead.

The two of them sit down for drinks and discuss their findings. Beltran's records indicate he is a sergeant on desk duty in a logistics office in New Londres, which is a discrepancy with the fact that he has access to highly-restricted access codes, and Bobbie reasons this could suggest he is actually an intelligence officer. Leelee trusts Esai's judgement, but Bobbie says the job is too easy and too profitable to be authentic, adding that Esai's judgement is clouded because he wants the money for his family. Leelee notes with a smile that Bobbie cares about Esai, and Bobbie admits that she just wants to stop him from making a stupid decision. The two women joke about their hitherto combative relationship, and Bobbie promises not to stop them or rat them out. Before leaving, Leelee offers Bobbie a reconciliatory answer to a question she asked long ago: Leelee didn't mean to kill the customs officer at the docks, she was defending herself from him and he got killed by accident.[6]

Feeling the space between[]

Dr. Okoye is wrapping Amos's wounds absent-mindedly as she stares, transfixed, at the glowing orb. Holden drags a wounded Murtry into the room and checks up on Amos, who tells him that he is ok while shooting glances at Murtry. Holden asks Okoye what it is that she saw when she fell through the orb. She replies that it was a strange feeling, like she could feel the space between things, and that there was a presence there heading towards her. Holden reassures her that he feels the same thing each time he crosses the rings, and that she's not crazy, but she replies that she may rather be.

Holden spots light from the top of the tower and decides to climb up, but before leaving he asks Amos not to kill Murtry, even though he deserves to die, because it's important to Holden. Amos offers no vocal reply but rather, agreeing with reluctance, softens his scornful stare to one of bereft sadness. Holden climbs to the top of the tower, and finds protomolecule ruins have emerged everywhere, covering the entire planet. He contacts Alex and Naomi allowing them to get each other up to speed. He asks them to get the Roci down there and pick them up for immediate evacuation, as they are exhausted and wounded. With Alex informing Holden that he's incredibly 800 kilometers away from where they started to which Holden expresses a lack of surprise, Naomi agrees to be there quickly.[7]

The dream of Marco is about to be writ large[]

Jorge and Victor want to keep torturing the Martian prisoner, but Ashford tells them that a person isn't just themselves, they are also everyone who cares for them. He warns that anyone they kill could have loved ones who would seek revenge and that it's important to show strength but also kindness, something that Marco Inaros knows well and which makes him very dangerous. The men ignore him, and Jorge goes back to the prisoner's cell. Meanwhile, the ship they are chasing appears to be throwing chromium in their reactor to make it look dirtier than it actually is, and Ashford orders to keep chasing them, sure that it is Inaros's ship. Looking over the pictures from the asteroid mine, Ashford realizes some of the rocks are missing and that Inaros plans to use them as a weapon of mass destruction, thinking he will attack Tycho and Ceres as retaliation to Anderson Dawes and Fred Johnson. Wondering why Mars would be involved in this, he goes back to interrogate the prisoner, only to find him brutally murdering Jorge. Victor walks in and, in a rage, shoots the Martian to death before collapsing in tears over his brother's dead body. Ashford sighs and sits down in frustration.[8]

Back on the Rocinante[]

Murtry wakes up chained to the Roci's med-bay, with Amos staring at him from the neighboring chair, as his fingers get regrown. Alex finds Lucia, who laments that she did all the things she did to save her family, and now she isn't going to see them again. Alex offers to get them aboard for a goodbye, but she is sure they won't want to see her. Alex convinces her to not make the same mistake he did, and tell her family how she feels while she still can. Meanwhile, an exhausted Holden remembers he hasn't reported to Avasrala in a while as Naomi makes him some coffee. They talk about how the Belter community will be able to stay on Ilus because all the people who started the violence are either arrested or dead, but Naomi points out that also includes Lucia. Holden reminds her that Lucia did get a lot of people killed, but Naomi laments that Earth will make an example out of her regardless of the fact she didn't want to hurt anyone, and that she won't get the chance to redeem herself like Naomi did. Holden decides that he will lie on his report, saying that Lucia died when the Edward Israel attacked the Roci and thus freeing her from punishment.

On Earth, Avasarala receives Holden's report: The ruins are inert, and the only danger on Ilus emerged when humans accidentally brought the protomolecule on the planet, which they have now ensured will not activate them again. The surviving Belters and RCE personnel have decided to join forces and stay on Ilus to rebuild the colony and continue their scientific analysis. Holden and crew will help the Barbapiccola get back through the Ring and sell their ore, and they will escort all detainees back to the Solar System to stand trial.

Avasarala has a narrow 2% advantage over Nancy Gao in the polls, and Avasarala's aide thinks that, since it was her who sent Holden to Ilus, they could turn this to their advantage. She points out that, quite the opposite, the story from Ilus is about Earther scientists and Belter refugees working together to survive on an alien world where they made amazing discoveries and earned a lot of money, while the villains are dead OPA extremists and murderous corporate security who were defeated by the unified forces of good. This is the perfect narrative to vindicate Gao's policies, and her insistence on colonization of the Ring Worlds.[9]

Bobbie follows a hunch[]

Bobbie keeps digging for background on Beltran, and finds that one of his co-workers in the logistics office that employs him is a protomolecule researcher. Going to confront him, she finds him dead of alleged cardiac arrest. She calls Esai, who ignores her call. She arrives at the meeting point as Esai and his people are ambushed and killed, except for Leelee who Bobbie yells at to get away, while the ambushers escape with the merchandise. Bobbie tries to chase after them, but they leave a bomb behind and it explodes, causing the glass dome to come crashing down, sweeping the cranes and platforms and turning the entire docks into a massive wreck. Bobbie finds Leelee crying over Esai's body and drags her back at the last moment through the closing emergency doors.

The two of them successfully sneak through and quickly blend into a crowd inconspicuously, which is looking in horror at giant news screens depicting the disaster. Bobbie says that the plan all along was for everyone involved to die, but Leelee points out that the mastermind couldn't have been Beltran as he's also dead. Bobbie knows that there was stealth technology in the containers that the ambushers stole, which means that someone very powerful was involved in the exchange. Leelee is scared and decides to get off planet to her cousin on Ceres, and she offers Bobbie to come with her, but Bobbie plans to stay and get to the bottom of this conspiracy. Leelee apologizes for getting Bobbie in this situation, but Bobbie reassures her that, at least now she has something to do. The two of them say a wordless goodbye and part ways.[10]

Last words, to a friend[]

Carol Chiwewe is overseeing the evacuation of the ruins, while Dr. Sarkis is there in person, next to Dr. Okoye. They talk with Holden on the Roci about building a camp near the ruins so they can study it more thoroughly, as Dr. Okoye wants to understand exactly what it is that happened between these two ancient alien species. Sarkis tells Holden that he'll be there to watch Okoye's back, and the two of them share a meaningful look. As Holden heats up some food, he assures them that he'll get the UN to give them any resources they might need. Sarkis asks if the artifact might still be dangerous, and while Okoye is confident, Holden says they should make sure that humanity doesn't become the next space faring species to be wiped out by it.

Felcia is on the Rocinante, video calling with Lucia and Jakob, who have adopted Chike as their son. She plans to ensure the Belters sell their ore, and then she will go to Ceres to attend university, something her parents are reassuring and supportive about. When the video call ends, Alex notices Felcia lingering over the empty screen.

Holden and Naomi carefully remove the protomolecule remains from the Roci's cargo bay. Holden laments that the last thing he said to Miller was that rain doesn't taste like anything, which are "shitty last words to a friend." She asks him what he would say if he had the chance to say something else, but he doesn't reply. She leaves him alone to set the flight path back to Earth, and he addresses Miller, though he is not there, saying that Miller was right about everything, that he warned them but they are charging through the doors anyway and that if they have any chance to survive what comes next, it is thanks to him. As he closes the lid on the safety box containing the protomolecule sample, he places a hand on it, and finishes with: "Rest in peace, brother."[11]

Promises to keep[]

The Roci launches the sample towards the sun, and the crew watch on the ship's 3D holographically-projected display as it approaches its destination and eventually vanishes. Amos's fingers are fully grown back, and he proclaims that he plans to test them out, before heading out of the command deck.

Naomi receives a wanted person notice, depicting Marco Inaros. She sends Fred Johnson a message, asking for his help with locating the son she had with Inaros, named Filip, before he gets killed due to the price on his father's head.

Amos arrives at Murtry's cell, and Murtry sarcastically says that the suspense is killing him. He asks Murtry if he is fully healed from his leg injury, which Murtry confirms but asks why Amos cares. He replies he doesn't want to "beat the shit" out of him if he's "gimpy", and Murtry gets up, preparing to face the confrontation about to ensue. Amos tells him that he liked Chandra, and is angry that Murtry forced him to kill her, but Murtry interrupts him with a punch to the face. Amos turns to Murtry with a bloody smile, and says "thank you" before attacking him.

Arjun watches Nancy Gao's inauguration speech, as she defeated Avasarala in the election. Avasarala arrives and tells him that Gao has decided to send her to Luna, which Arjun says she could refuse but Avasarala doesn't want to look ungracious to the public. She concedes her defeat and offers that they could have fun on Luna, as she can't remember the last time they went on vacation. Arjun doesn't remember either, and says he'd rather stay on Earth so that they can both have time to adjust. Avasarala realizes Arjun is mad at her, which he denies, but despite her pleading with him to go with her, he tells her to go alone and walks away.

Later, Avasarala walks in her nightgown through the UN Headquarters, and enters the Secretary General's office, which will soon no longer belong to her. She records a message of advice to leave for Nancy Gao, sharing that she didn't want this job but couldn't let it go after she had it, and that Gao won't have it easy, but that she'll be rooting for her. She offers that their work is important, but it doesn't define all that they are, and warns her not to lose the rest of herself while doing it. She laments that, when Gao's time on the job ends too, she will want a life to return to. As for the direction Gao is taking Earth, Avasarala remarks that one of the two of them is wrong, and she believes it's Gao, but she hopes that it's herself. She wishes Gao good luck, adding that their future is in her hands now. Avasarala gets up, and looks out the office's windows one last time, over the skyline of New York.

Just then, she gets a message from Bobbie, telling her that she can't trust anyone else to tell and that there's a Martian conspiracy to smuggle weapons to Belters, though Bobbie doesn't know for sure who is involved and what it's really about. She says that, if Avasarala still wants to work with her, Bobbie accepts her offer and says she thinks they both need each other. Avasarala muses aloud to the empty room, "Bobbie,… your timing sucks!"[12]

Tili go[]

In the Belt, Marco Inaros is overseeing a bunch of asteroids in the process of being cloaked in stealth technology. The screens on his ship glitch out, and Marco realizes they are under attack. Ashford and his crew storm the ship and a firefight ensues, during which finds Ashford's crew getting picked off. Ashford manages to wound Marco and hold him at gunpoint, but he is ambushed by an armed and grown up Filip. Marco calls Ashford a traitor to the Belt and gloats that he cannot stop what's coming.

Ashford is put in an airlock to be executed, though he is relaxed and nonchalant about it. He covertly begins to record their conversation as he mentions Marco using the asteroids to attack Tycho and Ceres, but Marco mocks Ashford for not being imaginative and far-reaching enough. He finishes with "die in darkness, beratna" before releasing the airlock. Ashford smiles a contemptuous smile at Marco, and begins to sing the song he sung for his daughter when she was a baby, as he floats out into space. Marco's ship leaves Ashford's dead body behind, while the device on his sleeve stops recording.

Marco hurls the stealth-coated asteroids at Earth. Filip asks him what they will do about the asteroid spotters, but Marco reveals they used the Sojourner as a way to scope out the adversary's capabilities and to minimize chance of detection. But even their best technology is barely able to penetrate Martian stealth technology. The Earth will never see it coming.[13]



Guest Starring[]




  • Naomi calls in the favour she had Johnson agree to in "Back to the Butcher", that in exchange for agreeing to bring the Rocinante to Tycho Station, he find someone (Filip) for her.
  • As with other episodes, there are minor misspellings or typos in the chapter/scene titles seen when using the X-Ray feature.
    1. "on line" should be written as a single word not as two words.


  1. Icon-wgaw-24x24.png
  2. Icon-twitter-22x22.png  Tweet from Breck Eisner
  3. Season 4, Episode 10: "Cibola Burn" ("Back online" [00:01:13])
  4. Season 4, Episode 10: "Cibola Burn" ("The tether is cut" [00:03:02])
  5. Season 4, Episode 10: "Cibola Burn" ("Putting hate aside is talk" [00:04:12])
  6. Season 4, Episode 10: "Cibola Burn" ("Comparing notes" [00:09:39])
  7. Season 4, Episode 10: "Cibola Burn" ("Feeling the space between" [00:12:27])
  8. Season 4, Episode 10: "Cibola Burn" ("The dream of Marco is about to be writ large" [00:16:39])
  9. Season 4, Episode 10: "Cibola Burn" ("Back on the Rocinante" [00:18:17])
  10. Season 4, Episode 10: "Cibola Burn" ("Bobbie follows a hunch" [00:22:28])
  11. Season 4, Episode 10: "Cibola Burn" ("Last words, to a friend" [00:28:25])
  12. Season 4, Episode 10: "Cibola Burn" ("Promises to keep" [00:33:09])
  13. Season 4, Episode 10: "Cibola Burn" ("Tili go" [00:39:32])

External links[]