“They made their own clouds,” a man from Earth says in the fourth season of The Expanse, as he looks down at a terraformed Mars. “Brings to mind the people who built the great Gothic cathedrals. Knowing they’d be long dead before their work was finished, trusting their great-grandchildren would lay the final stones. We’ve lost that kind of generational thinking on Earth. Here, you see it in everything they do.”

It’s easy to get swept up in the big ideas of The Expanse. Based on the books by James S.A. Corey, it breathes gritty, grimy life into a future where humankind has colonized Mars and the asteroid belt, and now, thanks to a mysterious but probably insanely dangerous stargate, can reach a dizzying array of other star systems. There’s a Sagan-sized vastness to its perspective, where structures that are billions of years old loom on alien horizons and Lovecraftian terrors—given sci-fi names like “the protomolecule”—lurk both among the stars and, for some unlucky bastards, inside our guts.

But all that feels like window dressing for what The Expanse is really interested in: Figuring out if humanity, as fucked up as it is, can adapt to survive whatever comes next. Bloody, generations-old conflicts surge between the inhabitants of a climate-flooded Earth, the militaristic settlers of Mars, and the Belters, the long-exploited miners of the asteroid belt whose delicate bodies are so adapted to space that they can barely set foot on gravity-mired planets. As The Expanse’s fourth season begins, there aren’t enough jobs on Earth or Mars, desperate refugees speed toward that insanely dangerous stargate, and most people are stuck somewhere between the machinations of the powerful United Nations, led by the hard-edged, filthy-mouthed Chrisjen Avasarala (Shohreh Aghdashloo), and the brutal tactics of self-righteous terrorists who work to upset the tenuous, cruel balance that barely keeps war at bay.

As The Expanse has gone on—after three acclaimed seasons, it was canceled by Syfy in 2018, only to be resurrected, for this season and more, by megafan Jeff Bezos—its focus has slowly shifted from the likeable, well-intentioned, and terminally doofy spaceship captain James Holden (Steven Strait) to a trio of women: the wonderful, no-bullshit Avasarala; the driven, powerful Martian soldier Bobbie Draper (Frankie Adams); and Camina Drummer (Cara Gee), the captain of a Belter ship who uses her sharp gaze and sharper words to slice through the spaces between factions. The Expanse is full of other great characters—I’m partial to the muscle-bound, gun-toting Amos (Wes Chatham), who, depending on his mood, is either incredibly sweet or the very last person you want to meet—and unlike a lot of other genre TV, it gives each of them time to breathe. (Except when they’ve been shot out of an airlock.) This is a complicated galaxy full of complicated people, and as they’ve grown, The Expanse has only gotten smarter, stronger, and more addictive.

At least in the six episodes provided to critics, that trend continues in the fourth season. There’s a bump or two—with all these moving pieces, it takes a bit of time to regain one’s footing, and this season’s apparent villain, Adolphus Murtry (Burn Gorman), is adequately dickish but no match for last season’s sympathetic and frightening Klaes Ashford (David Strathairn). But with a ship of Belter refugees bursting through to another world, the season quickly gains a dark, open-ended vibe that isn’t too far from a Western: We’ve found a new frontier, and something’s out there, past all our squabbling and killing.

In the future of The Expanse, we’ve already lost our fight against climate change, and our explorations beyond Earth have chiefly led to new variations on age-old conflicts. Just like in the real world, the question looms: Is it even possible for us to be better? Or is what we’ve always been—a back-stabbing, ruthlessly parasitic species that self-sabotages at every opportunity—just what we are, regardless of if we’re on Earth or in the stars?

All 10 episodes of Season Four of The Expanse stream on Amazon Prime Video starting Friday, December 13.