Sequels that are better than their originals are rare. Rarer still are sequels like Aliens, which managed to improve on an original that was pretty damn good while essentially changing both the genre and the dramatic thrust of that original. 30 years ago today, the James Cameron-directed Aliens hit theaters, and with all due respect to, say, The Empire Strikes Back, it stands today as the greatest sci-fi sequel of all time.

Here’s what else: while the culture busily scrambles to try to get a handle on the idea of an all-female Ghostbusters, the Alien franchise proved that the best way to infuse your action franchise with feminism is to have it baked in from the beginning. Well, nearly the beginning. However unlikely it might seem, it was James Cameron’s vision for a sequel toRidley Scott’s Alien that turned Ellen Ripley from a horror-movie survivor to a capital-F Feminist Icon.

From our perch in 2016, when franchises get turned out with efficient quickness, looking back at Aliens feels like looking at something strange and unfathomable and, well, alien. A sequel that waited seven years and when it did come back, the scream-less silence of a horror movie in space starring a motley crew of trash collectors from the future and one very unlikely Final Girl gave way to an action movie set on a terraforming colony starring a bone fide action heroine. It’s easy to forget after 30+ years of nostalgia, but the Ellen Ripley of the original Alien was neither a leader nor much of a fighter; she made it to the escape pod at the end of the movie because she was a survivor, but it was in a decidedly horror-movie sense.

James Cameron stepped in to direct the sequel as a straight-up action movie, and while he kept Ripley, he had her evolve. Hardened by her experiences with the xenomorph aboard the Nostromo, Ripley emerged from her cryo-pod mad as hell. And when she ends up getting pulled into the mission to the terraforming colony LV-426, where the aliens have begun to run amok, it’s in a very action-star/Rambo kind of way. After 57 years in hyper-sleep, Ripley is literally too old for this shit, even if she doesn’t look it. If nothing else, the genre swap between Alien and Aliens allows Cameron to avoid telling the same story twice. He famously looked to movies about the Vietnam war for inspiration, and the ragtag band of soldiers who assemble to accompany Ripley (including Bill Paxton and Michael Beihn) bear that out.

But it’s not just that Ellen Ripley evolves into an action hero in Aliens; it’s that her entire character takes on a an entirely new complexity and depth. After she emerges from hyper-sleep, the sleazy company executive who debriefs her (Paul Reiser, in his finest role, all due respect to My Two Dads) informs her that her daughter has recently died of old age. Then, when she gets to LV-426, she meets Newt, the little girl who survived the alien attack that killed her family. The motherly bond Ripley forms with Newt isn’t exactly subtle, but it infuses the entire rest of Aliens with urgency: Ripley’s not only trying to save her own life and kill the aliens; now she’s a mother with a daughter. By the time we reach that climactic scene where Ripley in the mecha-suit fights the alien queen (“Get away from her, you bitch!”), Ripley’s status as a mother figure — fighting an alien queen who we just saw laying a room full of eggs (that Ripley promptly torched) — is what makes that scene so iconic.

The themes of motherhood, which where essentially absent from Alien and purely a creation of Cameron’s vision for the franchise, would remain a hugely important part of the Ripley character long after Cameron left Aliens behind. From the creature she carried inside her in Alien 3 to that sad, awful clone she spawned in the ill-conceived Alien: Resurrection, Ripley-as-mother became a huge part of the character, as much as her toughness and her uncompromising will.

Aliens is the best sci-fi sequel of all time in part because it doesn’t have to continue a story. Cameron was free to take the two loose ends of Alien — Ripley in hypersleep and the idea of more aliens out there that the company might want to get their hands on — and make his own movie in the Alien sandbox. It’s a marvelous, gorgeous, pulse-pounding act of creation.

[You can watch Aliens on Amazon Video.]