An astute craftsman even on his worst days (read: “A Good Year”), 74-year-old Ridley Scott has already earned his place in movie history by helming the equally impressive and influential “Alien” and “Blade Runner.” He hasn’t returned to the realm of sci-fi in the three decades since, but between plans for a sequel to the latter and this weekend’s “Prometheus,” a distant prequel to the former, Scott is returning to the genre well with no shortage of panache or heady concepts at hand. Whether those concepts fundamentally compensate for the occasionally rough-hewn execution that follows remains up for debate.

Through glimpses of violence on a cellular level, the wordless prologue aptly establishes the ominous/opaque tone and primary creative/destructive themes. We then jump forward from what would appear to be the beginning of Life as We Know It on Earth to the year 2089 A.D., when archaeologists Elizabeth Shaw (Noomi Rapace) and Charlie Holloway (Logan Marshall-Green) discover cave paintings in Scotland that corroborate their theory that someone out there -- “Engineers” -- has made the same impression on several civilizations across thousands of years and wants to be found. For him, it’s the pursuit of science; for her, it’s a quest for God.

It’s 2093 by the time mogul Peter Weyland (Guy Pearce, beneath an unfortunate amount of old-age makeup) bankrolls their trillion-dollar expedition to the farthest reaches of our universe aboard the spaceship Prometheus, and along with corporate liaison Meredith Vickers (Charlize Theron), android associate David (Michael Fassbender), ship’s captain Janek (Idris Elba), and others, Shaw and Holloway touch down on LV-223 and enter the nearest pyramid they can find -- home to ancient corpses, countless capsules of goo, and a statue of a human head.

Before I say anymore, and before anyone else can say “Don’t take off your helmets” and “Don’t touch anything,” best laid plans do very much go awry. Until that point, and even after, Scott maintains an admirable scale to the entire enterprise, allowing the eponymous ship to be dwarfed by the magnitude of space, skies and structures alike, and capturing every environment in gorgeous 3-D. The awe of the first hour is only bolstered by Marc Streitenfeld’s score, initially indebted more to the rousing themes of John Williams than to Jerry Goldsmith’s eerie original compositions.

However, Prometheus was the tale of the Titan who gave fire to us mortals and was punished for stealing it from the Gods; “Prometheus” adheres closer to the legend of Icarus, in that it struggles to soar as it draws closer to things big, bold, and bright. The ostensibly educated minds aboard begin to behave even dumber than their blue-collar brethren on the Nostromo, and once sex and drugs enter the picture, it’s hard to ignore the slasher horror tradition that follows, albeit in glossier, gorier fashion. The anonymous half of a crew of 17 await extermination while the bigger stars ping-pong back and forth between the pyramid and the ship, and the larger, more fascinating “Frankenstein” variation that’s busy toying with the lofty dichotomy of faith vs. science becomes interrupted by a half-hearted family tragedy in the classical mold.

It’s hard to know whether Jon Spaihts’ original screenplay or Damon Lindelof’s subsequent rewrites are responsible for the hasty revelations and hidden motivations to come, or how much vital character development found its way to the cutting room floor before leads, who have hardly interacted before, find themselves agreeing on a deadly course of action. Others who fled a scene to specifically avoid trouble find themselves inexplicably stranded all the same, if only to help pick off the equally ancillary characters milling about. There’s a terrifically tense surgical sequence in the middle of the film that strains logic even as it shreds nerves, and that scene is itself wedged in between a rushed series of considerable deaths, developments, and reveals, none of which seems to carry much weight to our lead beyond the immediate physical toll.

Rapace carries those burdens well, though, struggling to give her philosophical dilemmas comparable weight to the frequent physical peril. Marshall-Green is a bit more foolhardy, and harder to like for it. Theron begins as the steely voice of reason before bending her performance to the will of a most improbable subplot, while Elba’s more pragmatic role permits him to most directly channel the working-man charms of “Alien’s” original cast. Above all towers Fassbender’s understated turn as David, a soulless creation who nonetheless seems to spite his human creators and operates with eerie precision towards cryptic ends. While they sleep, he alternates between watching their dreams and taking in “Lawrence of Arabia,” as if seeking advice on how best to handle stolen fire. Even as the plot’s ambiguity borders on outright inscrutability, Fassbender operates with a distinct, if unspoken, sense of purpose that leaves scenes less fascinating without him.

Thankfully, that pervasive sense of dread sustains itself for long enough to offset the film’s frustrating need to introduce a clear-cut baddie and sequel signposts. (After all, it’s no spoiler to point out that this project takes place before the crew of the Nostromo has even been born.) Alas, this is the messy business of having a few too many engineers attempt to simultaneously evolve a franchise both forwards and backwards. In the end, Ridley Scott means to bring wonder and horror back to summertime spectacle, and “Prometheus” mostly succeeds in that regard. (Mostly.) As David himself might advise, in the borrowed words of T.E. Lawrence, the trick to enjoying it is not minding its faults.

Grade: B-