The Expanse’s third season ended on June 27th on the Syfy Channel. The final episode, “Abaddon’s Gate,” is the last installment of the show shot for Syfy. Over the course of The Expanse’s latest arc, an expedition involving every faction of Earth’s solar system discovered the true nature of the protomolecule that’s been the series’s major mystery, and confirmed the dangers and potential gains it represents for humanity.

Spoilers ahead for the series, as well as some of the James S.A. Corey novels the show adapts.

Shortly after Syfy announced that it wasn’t renewing the series for another season, The Expanse underwent a soft reboot with the episode ‘Delta-V”, closing out the threat of all-out war depicted in the novel Caliban’s War, and pivoting to the next arc, adapting the third novel in the series, Abaddon’s Gate. That book followed Captain James Holden and the crew of the Rocinante as they accompanied an expedition made up of various spaceships from around the Solar System to investigate the ring gate that was constructed by an alien substance called the protomolecule throughout the show’s second and third seasons.

In this season’s final story arc, a fleet of ships from Earth, Mars, and the Outer Planets Alliance head out to the ring, and face problems when they arrive. A woman named Clarissa Mao (Nadine Nicole), is bent on exacting revenge from Holden, because he was primarily responsible for the downfall of her father, Jules Pierre-Mao. She sabotages the Rocinante, blows up a ship, and broadcasts a faked message from Holden claiming responsibility, prompting the rest of the expedition to try to take him out. To escape, Holden flees into the ring, and into a strange new world beyond it. It’s an empty space with a spherical station in the middle, and when the expedition attacks Holden and the Rocinante, it appears to defy physics, abruptly slowing everyone in the space down — causing enormous casualties amongst the crews — in an attempt to protect itself.

Unbeknownst to the rest of the crew, Holden had begun to see visions of Detective Miller (Thomas Jane), who died on Venus in season 2. The hallucination guides him to the ring’s station, where he learns what the station is, and what the protomolecule was designed to do: build an intergalactic transportation system, linking together thousands of worlds. The ring and station are a gateway to new places for humanity to go.

As this is happening, the expedition realizes that the station poses an incredible danger to everyone in the region, and to Earth itself. Belter captain Klaes Ashford (played by David Strathairn) hatches a desperate plan to destroy the ring with his ship’s powerful communications laser, which would protect Earth from the station, but leave them stranded. That plan, Holden realizes, won’t work: their attempts will show the station that it’s a threat, and it’s gearing up to wipe out humanity to save itself the trouble. In last night’s two-episode finale, Holden and his crew work to counter Ashford’s plans, ultimately de-escalating the situation, and convinces the station to open up gates to the rest of the galaxy.

Season 4 and beyond

Amazon picked up The Expanse for a fourth season last month, but if that hadn’t happened, this finale would have left the series on a satisfying note, wrapping up some of the bigger storylines, and leaving on an optimistic note that humanity could put aside their differences and work together, just as humanity is presented with this incredible opportunity to travel far beyond the Solar System and expand into the galaxy.

In the closing moments of season 3, Holden asks Miller what his intentions were to reactivate the gate system, and that humanity now has a new frontier, and that they won’t be able to resist the temptation to explore those planets and solar systems.

But he also notes that humanity still has its divisions and problems. Over the course of the show, we’ve seen the writers hammer home a key point. When humans left Earth to colonize the Solar System, they took with them many of its problems: wealth inequality, racism, and political turmoil. The events of the show’s first three seasons have demonstrated that people are prone to violence against other groups, and as they move out into the greater galaxy, those problems will continue to become a problem.

That’s going to be a stumbling block, because Holden saw something else while he was on the station: the gate builders created a vast network and a galactic civilization, but at some point, they began to sterilize systems as if it were containing a threat, to no avail: they were wiped out. If something could take out an intergalactic civilization like that, what chance will humanity have?

If the show continues to follow the books, we’ll see humanity face this particular challenge. The fourth book in the series, Cibola Burn, takes Holden and the Rocinante to a new planet called Ilus, where they work to deal with an unauthorized colony, and encounter the remnants of a vast, alien civilization. This season’s finale teases some changes from the books: Bobbie Draper appears to have joined the crew, while she vanished from the books for a spell.

But if the novels are any indication, the show won’t be shifting to exclusively explore the rest of the galaxy: Nemesis Games and Babylon’s Ashes deal with the longer story of the repression of the Belters by the likes of Earth and Mars, with devastating consequences in store for them — and the crew of the Roci. The books will also begin to explore the nature of the thousands of worlds beyond the ring gate, the mysterious creators who built them, and have begun to explore their downfall.

Hopefully with its new home at Amazon, The Expanse will get to cover some of that ground laid down by the books. If it does, we’ll be in for quite the ride when the show returns.