The Expanse Season 4 Ending Explained: Alien Bomb & New Villain

After making its grand return on Amazon Prime, The Expanse offered the same mind-bending alien science-fiction and intricate political drama fans have come to love and expect – here’s exactly how the season 4 finale played out. Over on the Syfy network, The Expanse spent its first 3 seasons constructing a conspiracy that encompassed the entire solar system. Set sometime around the 24th century, The Expanse takes place in a fully colonized system, with space travel allowing mankind to spread to new planets, asteroids and moons. Thus far, The Expanse‘s action has centered around the discovery of an alien technology called the Protomolecule, and man’s struggle to understand how to use it.

Previously, James Holden and his crew mates on board the Rocinante had been forced into the middle of this Protomolecule tug-of-war and found themselves desperately trying to avert all-out war between Earth, Mars and the inhabitants of the Belt. More worryingly, Holden’s connection to the Protomolecule provided a glimpse of a worse fate, where whatever wiped out the alien race that created the strange blue substance could be coming for the Sol system next. Before Holden could wrap his head around this nugget of doom, he accidentally opened gateways that spread across the entire galaxy, and the promise of new, untouched worlds triggered an exodus.

The Expanse season 4 focuses largely on one of these new worlds, Ilus, or New Terra, as it has since been christened. The Belters arrive first, looking to build a new home, but a private Earth research company soon pull up to make its investigations, led by the ruthless security chief Adolphus Murtry. If the character’s first name wasn’t enough of a clue, Murtry wages a campaign of violence against the Belters, forcing Holden to take sides instead of investigating the Protomolecule as instructed. Elsewhere, Bobbie struggles to acclimatize to civilian life on Mars and Earth undergoes political upheaval. Here’s exactly what happens at the end of The Expanse season 4.

Holden, Ilus & The Protomolecule

Since the latter half of season 3, Holden has been guided by an avatar of the Protomolecule in the guise of Joe Miller, but the connection went silent when Holden needed it most in season 4. Finally, it’s revealed that the consciousness of the real Miller had been grappling with the Protomolecule and had finally won out, allowing Holden to communicate with his deceased friend directly. Miller (the real one, though still speaking via the Protomolecule’s remote connection) recognizes that there’s a place on Ilus the Protomolecule won’t go, and suggests this could be the answer to everyone’s problems.

Travelling through the planet using a purple alien transfer system, Holden and Elvi Okoye find what Miller was leading them towards – a bomb left behind by the race that killed the Protomolecule creators. Miller explains that the two sides had once waged war across space and this bomb was a remnant of that conflict. By triggering it, Miller believes he can free himself from Protomolecule enslavement, while also decimating any semblance of the blue goo on Ilus. With Holden otherwise occupied beating up Murtry, Miller uses some nearby metal panels to create a rudimentary physical form and Elvi helps drag him into the bomb. This action appears to have the desired effect; Miller disappears, Ilus returns to its natural state, the Protomolecule structures scattering the planet become inert and the orbiting ships that had been halted by the Protomolecule’s influence are finally freed.

With Ilus now safe, the Belters are free to remain there, while Holden escorts Murtry back to Earth for a fair trial. Elvi reveals that while falling “inside” the bomb, she experienced the same foreboding feelings that Holden did in season 3 when he triggered the Ring Gates and both characters realize that something big could be coming in the near future. As an act of mercy, Holden lets Lucia free, despite her part in shooting down the RCE shuttle.

The Election On Earth

A world away from out of control paramilitary factions and alien black holes, Earth was facing its own difficulties as the citizens became increasingly frustrated with the leadership of Chrisjen Avasarala. Earlier in The Expanse season 4, a genuine contender to Chrisjen’s reign appeared in the form of ambitious up-and-comer Nancy Gao. Like Brexit in the U.K., the two sides campaigned on one single ideological issue – whether to allow citizens to travel through the Ring Gates or not. Having previously seen the damage caused by the Protomolecule, Chrisjen had been cautious to permit passage without knowing what lay ahead, but Gao recognized the desire of the people to explore this new frontier and put that promise at the forefront of her manifesto.

Throughout The Expanse season 4, various events had swung the pendulum of popularity back and forth between Avasarala and Gao, but the concluding chapter on Ilus described above finally decided the outcome of the election. As Chrisjen laments, the story of Belters overcoming deadly alien technology and an evil security team from Earth to claim a habitable new planet as their own was much too tempting for the rest of the system to ignore, and any reservations the population had about exploring the Ring Gates was washed away, guiding Gao to victory. Unfortunately, a job wasn’t the only thing Chrisjen lost as a result of the election. So determined was she to prove herself right about colonizing unexplored territory, Chrisjen abandoned her principles and even exploited the death of her own son for a political advantage. Since this moment, Chrisjen’s marriage appears to be in jeopardy.

The Hunt For Marco Inaros

While Marco Inaros played a key supporting role in The Expanse season 4, the charismatic criminal will likely be the prime antagonist of the upcoming season 5. Predictably, not all Belters are content with the truce the O.P.A. have with Earth and Mars in The Expanse season 4, and believe that not only will the two planets continue to exploit and oppress them, but that the pattern will continue in the new worlds opened up by the Ring Gates. According to Marco’s philosophy, the only way forward is striking back against the Inners, with both Earth and Mars weaker than ever before and susceptible to attack.

In the finale episode, the first stage of Marco’s plan in revealed. The disused military equipment Bobbie had been helping to smuggle off Mars has been ultimately finding its way back to Marco. Additionally, the purpose of Marco’s attempted strike on Earth during the election date was merely to test how the planet’s defenses would respond to incoming projectiles. With this information and his stolen Martian gear, Marco launches a missile strike on Earth that will penetrate the planet’s defenses. The extent of Mars’ involvement with Marco is currently unknown. It seems that many of the terrorist’s Martian contacts were merely acting for financial gain, with little idea of how the equipment would be used. However, Bobbie discovers that the conspiracy goes much further up the food chain that she thought and involves scientists working on both the Ring Gates and the Protomolecule, hinting at a potential alliance between Marco and a Martian splinter group.

In a final twist, it’s revealed that Naomi’s son Filip has already been brought under his father’s influence. While Naomi was hoping to find Filip before Marco, it seems that the pair have been working together the entire time, with Filip a key member of the crew that will soon become known as the Free Navy and a young Belter who already harbors hatred towards Earth and Mars.

The Expanse season 4 is currently available on Amazon Prime Video.

About The Author

Craig Elvy
(3643 Articles Published)

Craig first began contributing to Screen Rant in 2016, several years after graduating college, and has been ranting ever since, mostly to himself in a darkened room. Having previously written for various sports and music outlets, Craig’s interest soon turned to TV and film, where a steady upbringing of science fiction and comic books finally came into its own.
Craig has previously been published on sites such as Den of Geek, and after many coffee-drenched hours hunched over a laptop, part-time evening work eventually turned into a full-time career covering everything from the zombie apocalypse to the Starship Enterprise via the TARDIS.

Since joining the Screen Rant fold, Craig has been involved in breaking news stories and mildly controversial ranking lists, but now works predominantly as a features writer.
Jim Carrey is Craig’s top acting pick and favorite topics include superheroes, anime and the unrecognized genius of the High School Musical trilogy.

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