'The Expanse': Everything you need to know about the space opera

Dominique Tipper and Steven Strait in Season 5 of "The Expanse" on Amazon Prime Video.
Dominique Tipper as Naomi Nagata and Steven Strait as James Holden in Season 5 of "The Expanse" on Amazon Prime Video. (Image credit: Amazon Studios)
The short version

The Expanse is a "space opera" as much as it is traditional science fiction. Earth, Mars and those who live and work in the outer planets are fighting each other over control of a "protomolecule," which at first is seen as a super weapon, and then as a way to create super soldiers, and later opens doorways to thousands of new solar systems.

All this is set amid political intrigue, tribal dynamics, personal complications, and so much more.

The Expanse premiered in 2015 and ran for three seasons on SYFY before being canceled. A huge fan outcry ensued, and Amazon Studios resurrected The Expanse for three more seasons. Season 5 premieres on Dec. 16, 2020, and Season 6 — the final run — will start shooting in January 2021.

The Expanse — the sci-fi series born on SYFY that later made the leap to Amazon Prime Video — is ... expansive. (And that was before it grew into its fifth season, which debuts Dec. 16, 2020.) So this might get just a little complicated, but stay with us.

It's hundreds of years from the current day, and humanity has made its way throughout the solar system. Mankind is mostly made up of three factions — Earth and Luna (the colonized Moon), Mars, and those who live among the asteroid belt. They're known as Earthers, Martians, and Belters.

Earth and Mars don't get along so well these days. Earth has a massive space-based military. Mars has a smaller fleet with great tech, and it has a bunch of extremely dedicated marines. Belters are more about making an honest living and making money off of whom they can, and the "inners" (that is anyone not from the Belt) rely on them for minerals and trade. The Belt supported by a group called the OPA — the Outer Planets Alliance — which is a sort of labor union and occasional terrorist organization against the Inners. The OPA itself is made up of myriad factions.

Earth in this day and age is run by the United Nations, and it has all of the political machinations and in-fighting you'd expect. And that's important because certain members of the U.N. happen to be working in secret with a super-rich businessman on some super-secret things. We'll get to that in a second.

Meanwhile, James Holden (Steven Strait) isn't in command of an ice hauler, the Canterbury. (If you don't know why ice is important in space, read Seveneves.) He swears he doesn't want to be in command, but that lie is pretty easily seen through by all of us. Especially when he slyly ensures the Cant responds to a distress signal from a derelict ship, the Scopuli. That goes poorly, though. They don't find anything, and the Cant is destroyed by a stealth ship of unknown origin, leaving Holden, pilot Alex Kamal (Cas Anvar), mechanic/merc Amos Burton (Wes Chatham) and Engineer Naomi Nagata (Dominique Tipper) stranded. They're eventually rescued by a Martian ship — the Donnager.

And this is all in the midst of some mysterious blue goo that has been up to some seriously bad stuff on the asteroid where that derelict ship was found.

When the Donnager is mysteriously attacked by some "stealth ships," Holden and crew are rescued by a Martian ship. They escape in a smaller Martian frigate, the Tachi. Since the Donnager is now destroyed, they claim the Tachi as salvaged (gotta love the law of the sea in space) and rename it the Rocinante.

So we now have Martian and Belter ships destroyed by someone, and everyone's blaming everyone else. War is near.

(We're skipping over the crew dynamics here, but suffice to say there's a lot going on here, too.)

Meanwhile, on the Ceres space station, cop (excuse me, Star Helix officer) Joe Miller (Thomas Jane) is tasked — off the books — to find a missing girl, with whom he sort of begins to become obsessed.

That's the background. (We warned you it'd get complicated.) Here's the breakdown by season. It's worth noting that Seasons 1 and 2 don't really end on cliffhangers — they very much move from one to the next. But there are some major points in the middle of each season. The end of Season 3 definitely opens some new doors, though.

'The Expanse:' Season 1

The Expanse Season 1: Birth of a galactic conspiracy

The first season of The Expanse is, in many ways, about setting the table. There are a lot of players here in a lot of places. On Earth. On the Ceres station. On a number of ships. On stations throughout the solar system.

The over-simplified version is this:

A mysterious substance was found inside of Phoebe, an asteroid moon that orbits Saturn. It's determined to have originated outside of our solar system, the first time anything of that sort has been found. Scientists, backed by an extremely wealthy Earther businessman named Jules-Pierre Mao (François Chau), have been experimenting with it on Phoebe. But the protomolecule got out of control.

Mao's daughter, Julie Mao (Florence Faivre), has had enough of her old man and left to join up with the OPA. She's hacked into her father's electronic files and learned about the protomolecule experiments. She tells the OPA's leader on Ceres, Anderson Dawes (Jared Harris) about all this, and Fred Johnson (Chad L. Coleman), the leader of the OPA, sends a ship to steal the protomolecule experiment. That doesn't go well for anyone, and Julie Mao ends up being infected with the protomolecule. She locks herself in a seedy hotel on Eros station, on an asteroid relatively close to Earth.

Meanwhile, Detective Miller has been tasked off the books (and indirectly by Jules-Pierre Mao) to find Julie. He sort of becomes obsessed by this woman he's never met.

On the space side of things, Holden, Amos, Alex and Naomi, now on the mostly stolen Roscinante, are given safe harbor on Ceres by Fred Johnson. He needs their help (and their gunship) for a few things, though — including figuring out what happened on the Anubis, the ship that was carrying the protomolecule experiment.

The mysteries lead Miller and the crew of the Roscinante to Eros, where they all accidentally end up at Julie Mao's hotel room at the same time. (And in the middle of a gun battle to get to it.) They find her dead, covered in protomolecule. After they leave, the scientist working on the experiment takes Julie Mao's blood, fakes a radiation leak to lock down Eros station, and uses Mao's blood to infect the entire station population. It's a mass experiment/genocide.

Eventually everyone makes it back to the Roscinante. But the protomolecule lives on.

The Expanse: Season 2

The Expanse Season 2: Galactic war pigs have the power

Season 2 of The Expanse is more about war. UN Undersecretary Sadavir Errinwright (Shawn Doyle) — who has been working with Jules-Pierre Mao all this time to cultivate the protomolecule as a weapon — wants nothing more than to destroy Mars. Fellow Undersecretery Chrisjen Avasarala (Shohreh Aghdashloo) wants nothing more than to avoid war, which claimed her son years ago.

Mao, at this point, is playing Earth and Mars against each other. He's got protomolecule, and they both want it.

Meanwhile, Holden and Co. recovered a safe with a sample of protomolecule and hide it away on an asteroid.

The OPA and the Belters mostly are fine with the Inners shooting at each other.

We get some major new characters at the start of Season 2 — most notably Martian Marine Gunnery Sergeant Bobbie Draper (Frankie Adam). She's a badass, and that's without her power armor. She and her team are deployed on a ship en route to Phoebe station. A UNN ship is headed that way, too, and the race for the protomolecule — which the entire solar system now knows about — is on, with the UNN in the lead. Mars fires missiles toward the UNN ship, and everyone things they're about to have a really bad day. But the missiles continue on toward Phoebe station, destroying it. If Mars can't get there first, they'll make sure there's nothing there to find. In response, Earth destroys the Martian moon Deimos.

Phoebe and its protomolecule are gone, but Miller convinces Johnson and Holden that something has to be done about Eros, which still has tens of thousands of dead people infected with protomolecule on it. The idea? Load it up with bombs and use a huge ship Johnson was building for the Mormons to push the asteroid into the Sun.

That plan goes slightly awry in that the ship misses its target, and Eros — now powered and controlled by the protomolecule — starts heading on a collision course for Earth, which would be bad. Miller, who's found himself stuck on Eros thanks to one of his bombs being damaged, heads into Eros station and discovers a weird symbioses of Julie Mao and the protomolecule at the heart of it. Miller convinces Julie Mao to steer Eros away from Earth. It flies into Venus instead, killing them both.

In light of all this, Holden decides it's probably not a great idea to have a sample of the protomolecule just laying around, even if it's hidden in an asteroid. So they fire a nuclear torpedo at it. Only, they didn't — Naomi just made it look like they did. She later sends the coordinates of the sample to Fred Johnson, and two of the major players have protomolecule — the Belt, and Mars. (Earth, it turns out, doesn't actually have it under its control. It's Mao's.)

And that's just the first half of Season 2.

The back half finds us on Ganymede station on the moon orbiting Jupiter. It's mostly set up for farming, and both the UN and Mars have settlers there. They also have troops there, with a sort of DMZ setup keeping them separate. 

But the war flares up again, sending orbiting mirrors crashing down on the Ganymede domes, while at the same time UN forces are charging Draper and her Marines. It turns out, however, that they were running from something. And that something turns out to be protomolecule/human hybrid that Jules-Pierre Mao had been working on as a weapon for Earth. Draper comes face to face with it.

Holden, back on Tycho station with Fred Johnson, finds out that there are traces of protomolecule on Ganymede station. Conveniently, a Ganymede refugee (and botanist) named Prax (Terry Chen) had a daughter under the care of the same scientist who was believed to be working with the protomolecule on Ganymede. So they all head off.

The Roscinante ends up going up against the hybrid, and is nearly destroyed. They're able to lure it away from the ship with a nuclear warhead — protomolecule loves energy — and incinerate it in their drive plume. But Prax's daughter is still missing, and they're able to track her and the mad scientist to the Jupiter moon Io.

We're not done with Venus and its protomolecule yet. A science ship (whose crew includes someone close to Avasarala) races Mars to find out what happened there. As it descends to the surface, it's instantaneously broken down to its individual parts, much to the dismay of its occupants. (Which, by the way, included Adam Savage of Mythbusters, if you were playing close enough attention to notice.) That's weird, and important because it reiterates that that the protomolecule is learning. As the scientist on Phoebe tried to tell everyone, we can only learn about it by letting it learn about us. It took apart the ship because that's what it does — it breaks things down and makes new things.

And one more tangent: Avasarala knows that Errinwright was working with Mao was trying to start a war. She's forced to meet with Mao on a ship in orbit, but is taking captive. Fortunately, she has Draper with her (Draper had been used during Earth-Mars negotiations in Ganymede peace talks, since she actually saw the hybrid. But she had enough of Mars' tactics and sought asylum with Earth), and they manage to escape.

The Expanse: Season 3

The Expanse Season 3: There once was a protomolecule from Venus

We pick right up where we left off. The Roscinante (with Prax still on board) heads to Io. Jules-Pierre Mao has already arrived, and he's ready to shut down the project after playing with the children. But he then sees how the the hybrid boy on Io is communicating with the protomolecule on Venus, and that it's all connected. So he allows work to continue. 

Meanwhile, the Roscinante rescues Draper and Avasarala. (Because of course it does.) They head to Io, where they storm the facility with the hybrid experiment. The kids have been sedated and loaded into rockets, which a UNN admiral working with Mao fires at Mars. If even one hybrid gets to Mars, it could kill everyone.

Noami — who is outcast for giving Fred Johnson the protomolecule sample — has a way to intercept the missiles. But it requires trusting Fred Johnson and the OPA to use nuclear missiles stolen from Earth's attempt to stop Eros from crashing into it.

That's the first half of Season 3, which wraps up with a giant protomolecule squid-looking thing emerging from Venus. (Told you they're not beyond major plot points in the middle of the season.) It eventually turns into a large ring positioned beyond Uranus.

The fleets all start heading that way. The Roscinante travels with the OPA fleet. Noami has left the Roscinante and is working on the OPA flagship, the Behemoth, which is the renamed Mormon ship. Draper is back with the Martian fleet. And the UNN is sending its ships, too.

Meanwhile, a Belter racing ship — whose pilot is trying to impress his girlfriend — decides to be the first to go through the ring. He flies dark and silent until it's too late for anyone to stop him, then speeds on through. Except when he gets to the ring, it turns on and decelerates him so fast that his body explodes. It's at this time that Miller — or something that looks like Miller — starts appearing to Holden. Is Holden crazy? Is he infected with protomolecule? Or is it the protomolecule reaching out?

Miller passes along cryptic clues. That's important because someone in the UNN fleet destroys a ship and fakes a message from Holden from the Roscinante, making it look like he's claiming the ring for the Belt and will keep anyone else from having it. It turns out that's the older sister of Julia Mao, who blames Holden for all of her family's troubles. (The United Nations, in trying to bring Jules-Pierre Mao to justice, also sanctioned his family.) So now the UNN wants to kill Holden. The Belter flagship wants to kill Holden so that Earth knows they have nothing to do with this. And Mars still wants Holden because he stole their ship.

Only one thing to do, then — head into the ring. Fortunately Miller gave Holden the key to entering. Slow way down. The Roscinante makes it in, but its communications were knocked out when it sent the fake bombing message. More ships follow.

So now everyone's in this super slow ring space, and everyone wants a piece of Holden. Miller convinces Holden the only thing he can do is fly into the nucleus of the ring space, dubbed the "station." Holden hops in a space suit and heads that way. As he floats along, Miller explains that, no, he's not really Miller, but some sort of construct in Holden's brain being used to figure out what the protomolecule is doing.

Once on the station, Miller tells Holden what to do. But Holden isn't convinced he isn't being used. Meanwhile, a Martian fire team led by Draper arrives. They end up firing at Holden, but the bullets are frozen in mid-space. A Marine then throws a grenade, which damages the station. The station then disassembles the Marine, just like it did the ship on Venus. Everything is connected.

About the same time the Behemoth is trying to figure out how to at least get a message out of the ring space. A scientist persuades new captain Klaes Ashford (David Strathairn) to use a nuclear detonation as an experiment, to see if it will help them learn more about why they're stuck. But reacting to the detonation, the station then lowers the speed limit inside even further. That causes every ship that was moving to rapidly decelerate, injuring thousands.

The Behemoth was meant to take Mormons to far-distant worlds over a hundred years away and has an (untested) spinning drum for gravity, which they get working. He invites all other ships to send their wounded to heal in the artificial gravity. At the same time, he believes firing the ship's powerful communications laser will pierce the ring and get a message out. But Holden, having seen that the ring actually is a portal to other solar systems, knows that the station will see that as a threat and not only kill everyone inside ring space, but everyone outside it as well. He knows this because he saw what happened to hundreds of other solar systems that interacted with protomolecule.

The only way out of this is to persuade all of the ships to shut down their reactors. This requires a battle on board the Behemoth, and pits Draper against her fellow Martians once again. But one by one, the ships shut down.

And that's when hundreds of other rings appear inside, allowing passage to hundreds of systems with habitable worlds.

Holden knows what's going to happen next — humans will go explore those worlds. And where humans go, death and destruction follow.

The Expanse: Season 4

The Expanse Season 4: The grass isn't greener on the other side of the ring

Season 4 of The Expanse finds us back in the ring space, with the OPA serving as custodians and gatekeepers, and Drummer in charge of Medina station. (That's the Mormon ship Navoo-turned-OPA Behemoth.) An alliance has been formed, and prospecting of all the new worlds has begun.

And just as Holden predicted, that's become a problem. A group of Belters settled on a world they call "Illus." (The Earthers call it New Terra.) They staked their claim on this planet rich in lithium, which they've begun to mine. But they didn't do so with the blessing of anyone else. And so Earth has no problem sending its own corporate mining team to do the exact same thing.

You'd think there'd be enough lithium to go around, but sharing makes for bad TV. And so it's not at all surprising that when the first RCE corporate ship descends on Illus/New Terra it finds itself being shredded by some sort of bomb or missile or explosion. Security chief Adolphus Murtry (Burn Gorman) — who's looking to shoot some homesteaders anyway — survives the crash with a handful of others and looks for revenge.

Meanwhile, Avasarala — still the U.N. General Secretary and running for re-election — sends Holden and the Roscinante to Illus/New Terra to see what's what and report back. And that's convenient, because Miller is still in Holden's head and wants a ride to the other side.

Of course as soon as Holden crosses through the ring all hell starts to break loose, starting with an attack on the settlement by some sort of metallic bug. That leads to the discovery of some thorn-looking structures sticking out of the planet, which leads to lightning strikes circumscribing the planet, which leads to the explosion of an island like some sort of fusion bomb, which leads to an earthquake and a shockwave and an tsunami, forcing everyone — Belters, Earthers, Holden and Amos — into the alien structure.

From left, West Chatham as Amos, Steven Strait as Holden, Cas Anvar as Alex and Dominique Tipper as Naomi in Season 4 of "The Expanse."

From left, West Chatham as Amos, Steven Strait as Holden, Cas Anvar as Alex and Dominique Tipper as Naomi in Season 4 of "The Expanse," which led the crew of the Roscinante to a planet through one of the ring gates. (Image credit: Amazon Studios)

As if that's not bad enough, the alien structure apparently is home deadly poisonous slugs, and everyone is going blind from some sort of green goo that sets up shop in the vitreous fluid in eyeballs. Everyone except for Holden, that is.

Meanwhile, back on Mars, Bobbie Draper is living with relatives and trying to find work now that she's been dishonorably discharged from the Martian Marine Corps. She gets wrapped up in a black market scheme, though, and ultimately telling Avasarala that, yes, she'd love to come work for her instead, because there's some sort of conspiracy going on in the Martian military and government.

Back on Illus, Miller has finally reappeared and has a way to shut down the whole "planet-as-a-fusion-bomb" thing. It involves using the structures as portals, and ultimately shutting things down. But it gets messy, and Miller is (we think) finally gone for good.

Life isn't peachy back in the Sol system, either. Drummer and Ashford have been searching for the terrorist Marco Inaros, and a bounty hunter delivered. But the OPA factions choose to let him live (and make him forfeit a ship and cargo he stole) instead of spacing him. Drummer went along with it to keep the factions united, but she's not happy about it. That decision turns out to be a poor one because Inaros is quickly back to his terrorist ways, and that causes a rift between Earth and the OPA once more. They need to actually get Inaros this time and stop him.

Ashford does manage to get to Inaros, but not before Marco and Naomi's son, Felip, get to Ashford. In the ultimate Scooby Doo trick, Ashford records Inaros disclosing his evil plot to shoot asteroids into Earth, then sends out the video just as he's being shot out an airlock, singing all the way, in one of the more wonderful death scenes you'll ever watch. 

Those stealth asteroids, though. They're gonna be a problem. And who has stealth tech? Mars. And who's just pulled at the first thread of a Martian conspiracy? Draper.

Plus, ya know, Inaros is still on the loose.

The Expanse: Season 5

The Expanse Season 5: Sins of the father and the search for a son

And that brings us to Season 5. Marco Inaros is back and will play a bigger role this season. He's now the commander of the "Free Navy," which comprises Belter and Martian ships the either were stolen, or joined the cause. (Though the latter was not necessarily always done willingly.)

Inaros is definitely more on the terrorist side than the freedom fighter side. (Of course, that depends on which side you're on.) "With the opening of the alien gates, we are at a crossroads," he says in the trailer. "No longer will Belters be persecuted. With this attack we will show our oppressors a strength they never thought possible." Between that and the asteroid we see flying toward Earth, that doesn't sound good.

The season starts out with the crew of the Roscinante mostly dispersed. Naomi and Holden are on Tycho station, with the Roscinante in need of some major work. But Naomi is restless now that she knows her son is with Inaros, and she desperately wants to keep him from following in his father's murderous footsteps. So she sets off to find Filip — and Holden isn't invited.

Alex has gone back to Mars to try to put his family back together, but that doesn't go so well. He ends up having beers with Bobbie Draper, who's investigating the black market trade on Mars and is even more convinced that someone high up on the Martian food chain is up to no good — and very likely working with Inaros. She and Alex set off to find out more.

Amos, meanwhile, has gone back to Baltimore — the first time since he left — after an old friend dies. There's not much left for him there, and those who do remember him aren't exactly thrilled to see that he's back. Oh, and Amos' name isn't actually Amos. 

And while he's back on Earth, Amos decides to go check up on Clarissa Mao, who caused such a ruckus in Season 5. She's in a maximum security prison, with her endocrine-enhancing mods shut down. It's maybe even worse than death. But things go more than a little crazy after Inaros' stealth-coated rocks start hitting the Earth, flooding the eastern seaboard and destroying the prison. Clarissa and Amos manage their way out, of course. 

Back on Tycho station, Fred Johnson still has his little bit of protomolecule, which Inaros is now determined to steal. Monica Stuart (Anna Hopkins) — who was shooting a documentary on board the Roscinante in Season 3 before becoming pivotal in getting everyone out of the ring space — conveniently runs into Holden in a noodle bar on Tycho station and ends up part of this whole mess. She gets kidnapped, Johnson gets shot and killed, and Inaros now has the protomolecule.

The back half of the season involves Amos getting off Earth with Clarissa and Amos' old gangster pal, and also with the space chase.

Bobbie and Alex are trying to track down the Martian black marketeers, and Holden and the Roscinante are trying to rescue Naomi, who's been held captive by Inaros. That, of course, is what ultimately brings everyone (OK, not quite everyone) back together, and sets up Season 6.

The Expanse: Season 6

The Expanse Season 6: One final showdown

Amazon Studios has confirmed that a sixth and final season of The Expanse will begin production in January 2021. No word on when to expect a finished product. But if Seasons 4 and 5 are any indication, it'd be toward the end of the year at the earliest.

And Season 6 will find the Roscinante without its pilot, Alex. Actor Cas Anvar won't be back after allegations of improper behavior toward women that surfaced in the summer of 2020, and his character was killed off in the finale of Season 5. It was a good death for the character, who likely won't be completely disappeared from the show. But Anvar himself is gone. 

Read our preview of what to expect from The Expanse Season 6.

Phil Nickinson

Phil spent his 20s in the newsroom of the Pensacola (Fla.) News Journal, his 30s on the road for AndroidCentral.com and Mobile Nations and is the Dad part of Modern Dad.