There is a simple truth at the heart of the Alien movie franchise: being chased by a monster is terrifying. Nobody likes being eaten alive. But the real terror of the series isn’t the prospect of being murdered by a runaway xenomorph. It’s the idea of being violated, and forced to give unnatural, fatal birth. Dan O’Bannon, screenwriter of the original Alien film, was specific about mining horror from the idea of men suffering rape and pregnancy. “I’m not going to go after the women in the audience,” he said in the making-of documentary The Alien Saga. “I'm going to attack the men. I am going to put in every image I can think of to make the men in the audience cross their legs.”

Over the course of six films, various directors and screenwriters have played with this theme in different ways. But Alien: Covenant, which opened May 19th in American theaters, is the first film since the original that puts the sexual violation of men back at the center. As a father who’s had more than one nightmare in which I realize I’m going to have to somehow give birth to some very large human babies, I was squirming in my seat during Alien: Covenant — and I loved every minute of it.

There’s no shortage of sexual imagery throughout the Alien movies, all grounded in the iconic work of Swiss artist H.R. Giger. Every film in the franchise has at least some sexual overtones, built into Giger’s phallic alien design, and the rape and pregnancy life cycle of the xenomorph species. But I’m going to skip the game of pointing out how various Alien spacecraft and creatures look like various genital organs. Instead, here are some thoughts on how this latest film does a masterful job of weaving this key theme into the action.

Warning: major spoilers for Alien: Covenant ahead.

The film opens with a group of colonists heading to a faraway world. Most of the crew members are married couples who are planning to start new families; their ship is carrying both adult colonists and frozen embryos. In a universe with no aliens, they would reach their destination, Origae-6, and commence with the heteronormative baby-making. Instead, they wind up on a strange planet, tracking a distress signal.

As they explore, two of the men encounter a bulbous fungus that releases microscopic spores that enter their orifices. Just as with the original Alien, it’s the men whose bodies are being invaded and turned into hosts and carriers. This time, instead of bursting through the chest, the unwanted alien babies emerge out of one victim’s spine, and another one’s mouth. The process is bloody, brutal, agonizing, and deadly.

The alien babies quickly threaten the rest of the crew, but they get some help from David (played by Michael Fassbender), the android introduced in the previous Alien film, Prometheus. David is an artificially intelligent machine with some serious daddy issues. He’s the “son” of Peter Weyland, owner of the corporation funding the colonization mission. In an early Covenant scene, Weyland tells David to regard him as a father, creator, and master. From the very start, David questions their relationship, unhappy to be treated like a servant by such a comparatively frail being. The original Alien finds horror in the idea of a man being forced to give birth. In Prometheus and Alien: Covenant, the notion of a man voluntarily giving birth to an artificial son stands next to that, as a sort of original sin.

David has been marooned for a decade, and has spent his time trying, in his own twisted way, to prove his superiority to the humans who created him by becoming a creator himself. As an android, he can’t impregnate anyone or give birth himself. So he’s become a breeder and zoologist, facilitating the process of turning a human body into an alien host. Through his experiments, Alien: Covenant returns to the original spectacle of a facehugger forcing its seed down a man’s throat, creating a new creature that will eventually hatch out of his chest.

The film adds an additional wrinkle to the theme of unnatural sex and birth: the notion of unnatural love. Covenant introduces Walter, a later-generation David-style android, also played by Michael Fassbender. Walter tells David that the Weyland Corporation has stopped making its androids so lifelike because their creativity and emotion alarmed their human owners. In place of love, Walter feels only duty to his human masters. Just as Alien circles around the idea of unnatural male pregnancy, Covenant has a corporation deciding that it’s unnatural and undesirable for a male android to want to create at all, much less leave any legacy behind.

David’s desire to create, and to forge emotional bonds, is what gives the movie a series of dark turns. When the female protagonist, Daniels, spurns his kiss, David vows he’ll do to her what he did to his first love, Elizabeth Shaw, turning a potential mate into a lab rat. David calls Walter “brother” and kisses him as well. There’s a suggestion of incest in Fassbender kissing himself on-screen, and it’s an unnerving moment. But it’s also a trick that gets him close enough to attack.

As the movie moves toward its climax, Scott drops any subtlety about the sexual themes, and puts two of the surviving crew members into a steamy shower, where they’re preparing to have sex. After being criticized for spending too much time on lofty ideas in Prometheus, Scott seems to be teasing the audience with a heavy-handed wink to slasher films. “Here’s your horror movie!” the direction screams, as the alien’s tail creeps between the couple’s naked legs, looking like a prehensile phallus. And then the alien pops its erect inner mouth through the back of the man’s skull, and out the front of his face. It’s a grotesque, bloody reversal of oral sex, but it’s also one of horror cinema’s favorite tropes: a titillating sex scene that becomes a repulsive death scene.

As the film ends, there’s a final nod to the themes of sex and unnatural male birth, a carrot meant to tease what will happen in the two sequels Scott has planned. We know the Engineers created humans and the black goo that incites aliens. But so far, the prequels haven’t shown us a true xenomorph, the biomechanical beast of the original Alien film. What might produce such a monster? We’re left with David, alone and in control of the colonizing ship, opening up the drawer of frozen embryos. With a coughing shudder, he regurgitates two alien embryos he had secreted away in his gut. It’s yet another moment of a man giving birth to an unnatural creature. But for once, it’s voluntary, intentional, and not fatal for the father. The Alien films come full circle in this moment. For the first time, a man has chosen to give physical birth to his alien children. And in the process, he’s planted the seed for untold horrors to come.