One thing’s for certain, Alien: Covenant is a Prometheus sequel. Ridley Scott doubles down on the 2012 prequel’s cerebral but ultimately sloppy storytelling, reveling in yet another cast of characters who make stupid decision after stupid decision in a misguided attempt to hoist ideology above character. In essence a film about discovering meaning, Prometheus failed to define its own, collapsing under the weight of its admirable ambition by throwing too much at the screen and having too little stick. By the end of that venture, everything remained a bit of a head-scratcher but Scott, for what it’s worth, attempts to make up for such here in Alien: Covenant. For its faults, Covenant brings the message of this deeply intertwined prequel series into focus here and its irreverent thesis is far darker than we might have anticipated: creation is nasty business. Our makers can be monsters. Gods and Devils are one and the same.

There’s a sense of disquieting narcism running through Alien: Covenant, revealed through its most interesting dichotomy – two android Michael Fassbenders facing off in ideological warfare. The film opens exploring David – the traitorous android with a crush on Peter O’Toole’s hairdo with whom we were acquainted aboard Prometheus – and his “birth” at the hands of Peter Weyland (Guy Pearce). David muses about lineage – asking his “father” where he came from. In a greater cosmic sense, the answer remains unclear; the question haunts Pearce to the furthest reaches of space. Perhaps obsessing from his first moments on Earth about his inability to reproduce, David dreams of fatherhood. But from monsters come monsters.

The other side to David’s coin is Walter (a rival Fassbender trying on an unassumingly flat Midwestern drawl.) David – whose cadence and inflection is eerily calming – breathes ambition, emotion and cruelty whereas Walter, an upgrade meant to tone down the robot’s humanity, displays evidence of a soul. In curbing his human qualities, he’s become more of a humanist. Walter makes sacrifices for his mortal counterparts whereas David sees kindness in their species as opportunity, seizing goodwill and harnessing it for nefarious malfeasance.

Scenes spent sprawled over unnerving zoological diagrams – some of the set design in Covenant is really aces – philosophizing about meaning, creation and genetic superiority is heady stuff, and deeply pertinent too; head and shoulders above the predictable slasher fare that dominates a good bulk of the rest of the film. Had Scott and Co. shone the spotlight on Fassbender(s) and expended the rest of the forgettable cast almost entirely, he might have had something truly special. As is, well, that’s just not entirely the case.

In between the thinking man’s horror moments that should have defined Covenant, we’re hostage to a wholly uneven, often surprisingly boring, actioner that stumbles its way from one scene to the next. Scott’s bumpy storytelling waffles between sour narcissism and humdrum Hollywood thrills that panders to a cast of characters even more bumble-brained and forgettable than those aboard the Prometheus.

Through little fault of her own, Katherine Waterston is mostly unmemorable as Daniels – a character who’s written to emulate Ripley without actually doing anything to make her interesting or unique – and she’s trapped in an awful haircut to boot. For a series that seriously invested minutes of precious screen time watching a male character tend to his mane on multiple occasions, Waterston winds up in bowlcut that would look embarrassing on a 12-year old. The only consultation of her intergalactic bob remains: in space, no one can hear you snicker.

Waterston is joined by an admirable cast with even less to do. Billy Crudup gets the hard shaft as Captain Oram, a man of faith who is built up to be someone of intrigue and then – like Elizabeth Shaw’s late womb infestation – just completely aborted. To invest time and narrative currency into a character only to sideline them entirely is just bad screenwriting; one of the more insufferable aspects of John Logan and Dante Harper’s clunky pages. Esteemed Mexican character actor Demián Bichir crops up as a mouthy merc but has literally nothing to do and little screen time, making you question how seriously his character’s involvement had been altered after his signing onto the project or in editing. Danny McBride probably gets out cleanest playing a rowdy, fly-by-the-seat-of-his-pants pilot who becomes the unlikely soul of the crew, even if he’s hardly a character worthy of spending more than twenty words on.

Let’s rewind to 2012. If you found yourself face-palming at some character’s dumb decisions in Prometheus – a biologist who decides to poke and prod at an unknown alien species; a geologist who gets lost in a tunnel he mapped himself; scientists who remove their helmets at the first sign of breathable air – just you wait to get a load of Covenant. There’s some judgement calls that go down that brandish a naivety rarely reserved for adult characters. Even a toddler with a jack-in-the-box would be more wary than some presented here. Another late stage, curtain call twist is sorely predictable from a long-shot, the writing on the wall in bright red streaks. Our heroes remain oblivious to the most obvious of tells, corralling them in with the kind of unaware doofus territory where Camp Crystal counselors splash around and Elm Street teenage residents doze.

The jumbled soiree of soft science fiction and hard horror of Covenant remains fitting to the Alien brand. An early explosion of spinebursters gets the blood pumping, if only to pump the breaks on them not soon after. The effects work is hit or miss and involve a few dreadful instances of CGI – the FX on the first alien reveal looks shockingly incomplete – that pales in comparison to the practical effects used to bring the original Alien to life 38 years ago. But when Fassbender is raving or the Xenomorphs are racing, Alien: Covenant can be sublime entertainment that suffers the unfortunate fate that it could have been – but is certainly not – great.

CONCLUSION: ‘Alien: Covenant’ is a nasty slice of sci-fi complicated by high highs and low lows; Michael Fassbender is outstanding doing double duty as ideological opposites; the lame stable of human characters, not so much. Seat-shaking blasts of horror evolve to predictable, intelligence-insulting twists; Ridley Scott hedges interesting, high-brow contemplative material in with humdrum action fare with low-grade effects work. Ultimately, ‘Covenant’ is a by-the-numbers alien slasher with aspirations to be so much more.