Wanna know what went down in The Expanse Season 1? It went a little something like this …
In the 23rd century, humans have colonized the solar system.
The U.N. controls Earth.
Mars is an independent military power.
The inner planets depend on the resources of the asteroid belt. In the Belt, air and water are more precious than gold.
Belters live and work in space, several of them members of the Outer Planets Alliance (OPA), an organization fighting for the interests of Belt inhabitants. Earth and Mars consider the OPA to be nothing less than a terrorist organization.
For decades, tensions have been rising - Earth, Mars and the Belt are now on the brink of war.
… second officer James Holden, chief engineer Naomi Nagata, mechanic Amos Burton, medic Shed Garvey and pilot Alex Kamal, due to being on board the Cant's short-range shuttle as they investigated a seemingly bogus distress signal from an abandoned ship called the Scopuli.
So who blew up the Cant? The attacking ship was a stealth vessel, and as only Mars can afford stealth tech, it would seem Mars has commenced with an act of war. The theory seems all the more plausible when Holden and his crew are taken aboard the Donnager, a Martian warship, for questioning.
Shed is killed during the attack, though Alex, Amos, Naomi and Holden manage to escape the doomed Donnager via the warship known as the Tachi, which they rename the Rocinante when they're offered sanctuary at Tycho Station.
Tycho Station is run by Fred Johnson, an OPA (Outer Planets Alliance) bigwig with a venomous past. He commissions Holden and his crew to track down 'Lionel Polanski,' the sole survivor of the Scopuli … a ship that Johnson himself commissioned for an OPA recon mission.
The Rocinante heads for Chartered Belt Asteroid BA-834024112, where Holden and his crew find the Anubis, the stealth ship that "killed the Cant." In Engineering, they find something seemingly growing on the reactor: spiraling layers of an amorphous, glassy, blue-green mass, clutching the reactor like a strangler fig. A bio-weapon of some sort? Or something else …?
Whatever it is, it gets a little frisky when the ship's power is turned back on, prompting the Rocinante to blow the abandoned Anubis to kingdom come. "Remember the Cant," Holden says as he watches the mighty ship go up in a nuclear fireball.
Holden and his crew head for run-down Eros Station, the would-be next destination of the Anubis, thinking that's where they'll find this "Lionel Polanski." They discover that "Lionel Polanski" is staying at the Blue Falcon Hotel, where they're attacked by thugs … and rescued by a man named Joe Miller.
Who is this Joe Miller? He started out in our story as a hard-boiled, hard-drinking detective for Star Helix Security at Ceres Station, assigned to track down Julie Mao, the daughter of the wealthy tycoon, Jules-Pierre Mao.
During his investigation, Miller discovers that Julie had ties to the OPA, which causes him to run afoul of Anderson Dawes, the OPA bigwig on Ceres. It would appear that Julie Mao learned about the 'bio-weapon' that Holden and company discovered on board the Anubis; she brought this information to Dawes, and he sent her and a small crew on board the Scopuli (via Fred Johnson) to intercept the Anubis to make sure the weapon wouldn't be used against Belters.
Dawes' influence on Star Helix results in Miller getting fired, though the former detective is now determined more than ever to find Julie Mao, whom he sees as the key to his own redemption after a life of corruption. His friend and colleague, Inspector Sematimba, tells him that the Anubis' short-range shuttle, the Anubis 1A, arrived at Eros Station and is currently racking up docking fees. Miller figures Julie was the pilot and heads for Eros.
Which takes us to when Miller meets up with Holden and the gang. Together, they enter the hotel room of "Lionel Polanski," where they find Julie Mao dead … and, somehow, changed via her exposure to whatever it is that the Rocinante crew found on board the Anubis.
Which takes us to poor Julie's story. When the Scopuli intercepted the Anubis in an attempt to seize the 'bio-weapon' on board, it was easily overpowered by the stealth ship and Julie was taken prisoner. The crew of the Anubis then set the distress signal on the Scopuli to attract the Canterbury, which the Anubis then destroyed.
Back on Earth, Chrisjen Avasarala, the U.N. Deputy Undersecretary, has been trying to find out who destroyed the Canterbury. She was initially quick to throw Mars under the bus but then started suspecting that James Holden himself was the culprit. However, after a visit to Holden's mother, Chrisjen doesn't believe the former farmboy is a terrorist.
Indeed, Julie's father is involved in the development of the 'bio-weapon,' which he refers to as the "protomolecule," found on board the Anubis, which is now being unleashed upon the citizens of Eros Station.
Despite being ravaged by radiation poisoning, Miller and Holden make it back to the Rocinante. Along with Naomi, Amos and Alex, they escape Eros Station just as it's almost completely overrun by the protomolecule. And they're now in hot pursuit of Dresden's ship …
The final moment of Season 1 has Kenzo, the spy commissioned by Chrisjen to keep tabs on Fred Johnson and, later, Holden and his crew, coming across a section of Eros that's been completely transformed by the protomolecule.