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The Expanse Wiki

"Saeculum" is the ninth episode of the fourth season of The Expanse. Overall, it is the forty-fifth episode. It dropped on December 13, 2019 as part of Amazon Prime streaming's full-season release strategy with season 4.


Holden and The Investigator race to save Ilus. Murtry puts his endgame into motion, putting the Roci crew's lives at risk.


And because it looks, The Investigator exceeds its boundary conditions[]

The episode begins with The Investigator experiencing visions of Holden, Miller, Ilus, and the protomolecule. He is trying to find clues about the destruction of the Ring Builders, but something is stopping him and keeps trying to wipe him out, causing him to lose his progress and be forced to start over, which is why he often has been forgetting things or repeating sentences when talking to Holden, and has been blocked from talking to him this whole time. He sees a vision of the Ring Builders being wiped out and, with a loud scream, is brought back to reality, where Holden is reeling from his screaming.

Holden asks The Investigator where he's been, and notes that he's not wearing the trenchcoat and hat he normally wears. The Investigator replies that the protomolecule has been using them both, and killing him over and over to stop him from finding out what he's been looking for. He tells Holden that being in his head and watching him give a shit about others helped the Investigator overcome the protomolecule, albeit temporarily. Holden welcomes him back with a smile.

The Investigator tells Holden that he's been flipping switches left and right and managed to pinpoint a place where, every time he tries to look into it, that part of him gets killed off. He adds "this planet's already a corpse, let's go kill its ghost" and effortlessly opens a door on the wall for him and Holden to walk through.[1]

Not safe yet[]

Dr. Sarkis is on call with Dr. Okoye, saying he wishes he could be there despite the deadly slugs and eye parasites, as he is no safer in a ship with a failed reactor and, if they're going to die, he'd prefer to die together with her. He hastens to add that he means it as a friend, and Okoye smiles and says that she knows what he means. She ends the transmission when she overhears Holden talking to The Investigator through the walls and finds the opening he left behind, walking inside to follow.

The Investigator leads Holden through dark corridors, telling him that there's something that waged war on the Ring Builders that they were unable to stop, and Holden agrees as he has seen those creatures. The Investigator is looking for any clues left behind to help them learn more about the mysterious aggressors, and the weapon they used to fight against the protomolecule. Dr. Okoye listens as Holden apparently talks to himself, while he tells the Investigator that he needs to get everyone out of the planet alive and asks him to focus on that first. The Investigator hopes to achieve that too, if he finds the weapon he is looking for, and though he is not sure that the humans will survive, it is truly their only option.[2]

Orbital correction[]

In the Rocinante, various small problems are starting to stack up as Naomi, Alex and Lucia try to ensure that the Barbapiccola stays in orbit. They call Felcia so the crew of the Barb can prepare for another thrust. Naomi instructs Alex on cutting off the Roci's unnecessary power drain, and they are left with enough power for roughly 5 more thrusts before they run out. Alex points out that they could get two or three more thrusts if the Belters dumped their precious lithium cargo, but Naomi asserts that they are not at that point yet.[3]

Murtry takes advantage of the situation[]

Murtry's officers on the Edward Israel are informing him on the Roci helping the Barbapiccola, which has bought it more than 20 hours in orbit but has also left both ships extremely vulnerable to a possible attack by RCE.

Meanwhile, Jakob sits next to Chike and comforts him, covering him with a blanket as he falls asleep. Amos looks on from afar and notices Jakob's gesture, nodding at him in approval.

He keeps walking around and burning slugs with his blowtorch, when Chandra approaches to check up on him. She gets straight to the point, saying that now that this problem's solved, the next will be food distribution, and invites him to go over to the RCE camp. Amos asks her if Murtry knows she wants to invite him, and Chandra retaliates that she doesn't get why he dislikes Murtry so much, and that if Amos knew him he'd know Murtry is fair and takes care of his people. Amos replies that Murtry reminds him of some bad people he knew back home, and warns her that just because someone is good to you doesn't mean that you can trust them. Chandra insists she trusts Murtry and that he and Amos are exactly alike: pragmatists who put their own people before everyone else. Amos replies that he would never lie to Chandra, and they stare at each other in tense silence before she leaves.[4]

One hell of a pep talk[]

Holden starts to stumble, as he's been awake for 3 days caring for and leading all the people in the settlement. The Investigator gives Holden a pep talk and gets him to keep going, leading him to a hole in the ground and asking him to jump in. He activates the hole somehow, to no visible effect until Holden puts his hand inside and touches a strange purple substance that glows in magenta light. As he asks The Investigator where it leads, Dr. Okoye catches up to him. She explains that she heard him talk to himself and overheard that he plans to save the ships, and she declares she is coming with him to help, as her people are also in danger, but he doesn't want her to come because he can only see The Investigator when he is alone. He explains that he needs The Investigator to guide him to something, though he doesn't tell her what exactly. Okoye watches as Holden jumps in the hall and falls through the strange glowing substance.[5]

Murtry asks Chandra for a report on the Belters, and she says that so far they have enough resources to remain peaceful. He tells her that the situation in orbit has changed and that they will need to take action soon, but Chandra points out that the Belters don't maintain a perimeter or have armed guards, unless you count Amos. Murtry pointedly asks her if she does count Amos as an enemy, and orders her to identify the locations of both Amos and Holden. He sees Dr. Okoye walk past and stops her to inform her that RCE personnel must stay within their camp for "safety" reasons. When Chandra gets a report that their soldiers can't find Holden, Murtry notices Okoye is nervous and asks her if she knows where he is. She tries to deflect by saying she doesn't know where he is right now, which is technically not a lie, but Murtry corners her threateningly and coaxes her into telling him.

On the Edward Israel, Dr. Sarkis is puzzled when Murtry's loyalists launch the ship's shuttle. He asks them why they are putting their last shuttle in danger when they still have RCE personnel who could get stranded down on Ilus. The guard says he's following Murtry's orders and, when Sarkis keeps protesting, the guard threatens him into compliance by putting a hand on his gun. Sarkis is shaken and, when the guards aren't watching, he brings out the shuttle's status and flight path on his screen and looks through it.

Amos finds a purpose[]

Amos walks by Dr. Okoye, who gets a call from Sarkis but her terminal is intercepted by a guard, as Murtry has ordered a communications ban. Amos approaches her to ask her if she's seen Chandra, but the guard threatens him that Murtry has forbidden anyone from talking to Okoye. Amos easily disarms and scares away the guard, and Okoye tells him that Holden is with Miller and that Murtry and Chandra went after him. Amos tries to find Holden, but his terminal is offline and there's no signal from him. He calls Chandra next, but she hangs up on him. As Okoye leads Amos to the hole Holden jumped through, he leaves a message to Chandra: that he is coming for her boss, and that she should not be there when he does.[6]

Miller and Holden get closer[]

Holden has fallen asleep on the way down, but is woken by The Investigator as he quickly approaches the floor at the end of the hole. He starts to panic, but the glowing substance safely deposits him at the end of the tunnel. As The Investigator begins to lead him through the ruins, he glitches back into his original persona with the hat, repeating the same sentences and leading him in the opposite direction. The hatless Investigator regains control and keeps walking, explaining that his creators are displeased that he is not following the rules he is supposed to and that the best way to deal with it is to wipe them out for good.

Okoye leads Amos to the hole, and he begins to take off his outer layers of clothing to jump inside. She announces that she will go with him and tells him not to stop her, but Amos replies that she doesn't need his permission to do anything, though warning her that it might be a one way trip. Okoye replies that they are all already on one.[7]

The tether shows signs of wear[]

As the Edward Israel's shuttle approaches Ilus, Naomi realizes the cable is too elastic and is stretching under the stress, making it more fragile. Felcia turns the cable's wheel on her end to put some tension on it. As Alex is calculating the ships' re-entry trajectories, he is perplexed to get a text message from Dr. Sarkis, when a video call is more customary. Sarkis asks if the Roci asked Murtry to send them a shuttle. Alex replies that they didn't, and Sarkis, watching for Murtry's guards, warns Alex that the shuttle is heading right towards them and that Murtry's goons threatened him just for asking about it. Alex thanks him for the warning and hails the shuttle first and then the Edward Israel, both of which are unresponsive. As the shuttle gets dangerously close, he warns Naomi and Lucia to brace, as it appears they are under attack. Alex destroys the shuttle, but the debris causes a gas canister in the Roci to fly uncontrollably around the cargo bay and hit Lucia, sending her spiraling into space.

Naomi secures a cable on the ship and then jumps out after her. Lucia is spinning uncontrollably and panicking, but Naomi talks to her and reminds her to breathe until she is close enough for them to grab each other's hand. Naomi talks Lucia down as they start dragging back towards the ship, and she thanks Naomi for saving her.[8]

You'll fall for the rest of your life[]

Murtry and Chandra land at the end of the hole's tunnel brandishing their guns, and check around to make sure there's no one hiding in the corners. They check their terminals to get a read on Holden from the ship, but find that they are offline down there. Chandra opens Amos's message and both she and Murtry hear it and, to her dismay, he orders that they will kill Amos first and then search for Holden to avoid having an armed killer at their back. She replies that, if it has to be done, she wants to be the one to do it. Murtry agrees.

The Investigator leads Holden up to the point that he knows the way, as he isn't sure exactly where the "bomb" they are looking for is, saying that he "knows where the corpse is buried, [they] will just need to dig a little to find the bullet". He opens a passageway for Holden that leads to a strange bridge that crosses over a deep chasm in the depths of the protomolecule ruin. At the center of the chasm is a structure, connected to hundreds of other bridges up and down the chasm. Holden asks how long he'll be falling if he slips, and the Investigator replies: "Hmm... Rest of your life" before flickering out and reappearing on the bridge. Holden hesitates for a moment before jumping on it and following him.[9]

Alex has one more idea[]

Alex and Naomi curse Murtry while they assess the damage to the Rocinante: They have lost half their thrusters due to the debris, a bunch of energy to fire the PDCs and a large amount of reaction mass to push against the spin caused by having thrusters only on one side of the Roci. The tether is making it difficult to deal with the arising problems, and also dragging the Roci back due to the Barbapiccola's weight. Alex also points out that, if the RCE goons attack them again, there is nothing they can do to defend themselves, as they lost a lot of ship power and can't spare to use the remains of it on their weapons. Lucia, desperate, says that they have to let the Barbapiccola fall. It's their only option to ensure that both them and the Belters survive. Alex and Naomi try to protest, but she declares that she's done getting people killed for her dream of staying on Ilus and that there's nothing left that they can do.

Alex has an idea, which Naomi thinks is risky: to use the Roci's railgun as a makeshift thruster. It will be a violent push and could snap the tether, but Alex points out that if that happens, they can evacuate the Belters as Lucia said. Naomi begrudgingly accepts, but leaves to try and repair the thrusters, telling Alex to inform Felcia about their plan.[10]

The eye of an angry god[]

Holden and the Investigator have reached the center of the structure, and found a strange glowing orb. The investigator says he needs to put himself into something physical. His plan is to connect his consciousness to every single machine on the planet, then walk into the orb and thus destroy all the mechanisms connected to him. As he explains this to Holden, he starts to glitch again and ponders that the protomolecule really wants to stop him from finishing his plan. He finds a suitable piece of machinery to use as a temporary body, saying they don't have much time and that Holden must guide the body as close to the orb as possible, but not let it touch the orb until the Investigator has connected to the rest of Ilus, which he says Holden will know has happened when it does. Holden notes that this really is the end. The Investigator says that it is his own end, but that he hopes Holden makes it out alive. He also tells Holden that there's a drop of the protomolecule underneath the Roci's cargo bay and that they should clean it up afterwards. Holden asks the Investigator about the glowing orb, noting that it killed the Ring builders whose rings humanity is now using, but the Investigator has nothing to offer on the matter, saying he got Holden this far, and the rest is up to him. Before the Investigator enters the mechanical body, Holden answers one of his earlier questions: Rain is just water. It doesn't taste like anything. The two of them smile at each other before the Investigator glitches out.[11]

Wei confronts Amos[]

Amos and Okoye arrive at the end of the tunnel, where Chandra is waiting. She tries to convince Amos to join her while he frantically looks for Holden, stating that both she and him are survivors, that they are used to killing people and getting their hands dirty and that it's usually others making a profit from their work but, this time, it can be them. Amos simply tells her not to do this and keeps looking for Holden, but Chandra yells at him, begging him to talk to her because she doesn't want to hurt him. He turns to look at her, and she says they both know he doesn't want to hurt her either. She tearfully offers that, if they can get through this one day of shitty choices, they will have enough to walk away from this life forever. Amos asks her if that's the story that Murtry has told her, but she believes it's the truth. He reminds Chandra that he promised to never lie to her, and so states that he is going to find Holden and, if she tries to stop him, he will go through her. Chandra, saddened, gravely replies that she can't let him do that. Amos hesitates for a moment before raising his gun and shooting a surprised Chandra to death. As she falls, she manages to shoot a bullet in his leg, wounding him. Murtry appears from the corner and shoots Amos in the hand, blowing his fingers off. As Murtry takes cover, Okoye rushes to help Amos, but he just tells her to get away.

Shots echo through the corridor as Okoye runs, following The Investigator's trail and calling for Holden.[12]

One last thruster[]

The crews on the Roci and the Barbapiccola are both secured, and Alex fires the railgun shot, which successfully boosts them, though not by much. Naomi has managed to repair two of the 11 damaged thrusters and, if they can buy her more time, she might be able to make their plan work. Alex reassures a worried Lucia that, in case everything else fails, they will ensure the crew of the Barbapiccola is rescued.[13]

Into the fire[]

Holden is waiting for The Investigator when a frantic Okoye arrives, informing him that Amos killed Chandra, that Murtry shot Amos and that he is now coming to kill Holden. He tells her to stay put and not touch the orb until he returns, and leaves her alone in the room.

She stares, perplexed but intrigued, at the strange sphere, when she is surprised to hear the Investigator's voice cursing. He asks her who the fuck she is, and she introduces herself, informing him that Holden left to save Amos, which the Investigator complains is bad timing. She realizes he is "Holden's ghost" and calls him Miller, and he asks her if she sees anything interesting in the room, so she points at the orb and wonders what exactly it is. The Investigator replies that, with enough luck, it is the off-switch to the entire planet. A strange robot made of triangular shards emerges from the wall and lands in front of Okoye, and the Investigator's voice booms from it: "Well, lady, you're going to help me".

Holden is running back through the bridge, when Murtry appears and blocks his way. He asks Murtry where Amos is and if he's alive, but Murtry says he didn't bother checking and just went around him. Holden threatens that, if Amos died, he will kill Murtry himself. The two of them exchange jabs back and forth, until Murtry jumps down on the bridge and draws his gun.

Okoye is leading the robotic body towards the orb, and asks the Investigator if he's really Detective Miller from Ceres. He replies that if he's not, he's definitely acing his Turing test. She walks the robot about a meter away from the orb, and he stops, preparing the fragments around it to do something.

Murtry tells Holden that people like him always forget that civilization has a lag time, like light delay, and Holden thinks that just because he is civilized, he brings civilization wherever he goes. Holden is pointing his gun at Murtry and tells him to put his hands on his head, but Murtry ignores him and continues on, saying that they are walking in the footsteps of history, in the ancient concept of the frontier. The banks and post offices and railroads come after, but they need bloodshed to be built, and Murtry declares himself the kind of man the frontier needs, while Holden is the kind that comes after Murtry's work is done. He tells Holden he should have stayed home until Murtry built his post office. Holden retorts that he met another man who used past genocides to justify his bullshit, but a friend of Holden's shot him in the face. After a couple of tense seconds staring at each other, Murtry raises his gun and the two men shoot at each other. Both are hit, but Murtry is hit worse and collapses to the ground, his gun falling into the abyss below.

Dr. Okoye watches lights appear in the walls as the Investigator's robot begins to approach the orb.

Murtry looks down at the chasm, which lights up as well, until Holden lifts him and turns him over. Murtry chides that Holden doesn't have the guts to finish him, but Holden replies that Murtry is already finished, as he will be brought to Earth, get judged in trial and then get thrown in a cell for the rest of his life, adding that's a thing called "civilization". He then walks past Murtry, leaving him alone.

Dr. Okoye helps the Investigator's robot align its panels and points it in the right direction. She watches as another robot attacks the Investigator, while a swarm of the deadly metal bugs descends towards her. She curls up underneath the orb and avoids getting hurt as the swarm passes through the orb and then clutters to the ground. The Investigator's robot also falls down, and when Okoye approaches, he says that he can't move at all.

The entire protomolecule structure begins to glow, startling Jakob, who keeps Chike close to protect him.

Naomi, Alex, Lucia and Dr. Sarkis watch astonishedly on their monitors as the entire planet lights up with a matrix of patterned pathways traced in bright blue emissions which, viewed from orbit, resembles an enormous computer mapping model.[14]

Elvi drags the hobbled mechanized Investigator along the floor towards the orb, and he urges her to accelerate as the lighting in the room starts to fluctuate and intensify. Holden walks in at the last moment and yells for her to wait, but she slips and falls through the orb, together with the Investigator's robot.[15]




  • As in past episodes, there were a few inconsistencies with spelling or capitalization on the chapter/scene titles when viewed via the X-Ray feature (2021-Feb):
    1. The name "Multry" was misspelled using an "l" instead of an "r"
    2. The character was labelled as "the investigator" in all lowercase instead of all uppercase as in the novel Cibola Burn and before that in Abaddon's Gate
  • A Saeculum is the length of time that is roughly equivalent to the full lifetime of a human being. [source]


  1. Season 4, Episode 9: "Saeculum" ("And because it looks, The Investigator exceeds its boundary conditions" [00:01:13])
  2. Season 4, Episode 9: "Saeculum" ("Not safe yet" [00:04:24])
  3. Season 4, Episode 9: "Saeculum" ("Orbital correction" [00:06:32])
  4. Season 4, Episode 9: "Saeculum" ("Murtry takes advantage of the situation" [00:07:46])
  5. Season 4, Episode 9: "Saeculum" ("One hell of a pep talk" [00:09:44])
  6. Season 4, Episode 9: "Saeculum" ("Amos finds a purpose" [00:13:15])
  7. Season 4, Episode 9: "Saeculum" ("Miller and Holden get closer" [00:15:57])
  8. Season 4, Episode 9: "Saeculum" ("The tether shows signs of wear" [00:17:54])
  9. Season 4, Episode 9: "Saeculum" ("You'll fall for the rest of your life" [00:22:06])
  10. Season 4, Episode 9: "Saeculum" ("Alex has one more idea" [00:24:24])
  11. Season 4, Episode 9: "Saeculum" ("The eye of an angry god" [00:26:35])
  12. Season 4, Episode 9: "Saeculum" ("Wei confronts Amos" [00:29:54])
  13. Season 4, Episode 9: "Saeculum" ("One last thruster" [00:32:02])
  14. Your phone looks like a computer because it is one but your phone doesn't look like that
  15. Season 4, Episode 9: "Saeculum" ("Into the fire" [00:36:29])

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