These days, none but the most naive, gullible and uninformed of moviegoers would ever fall for the déclassé claim that a horror film purporting to consist of found footage is, in fact, real. 1999's "The Blair Witch Project" was one thing, since it started the trend, but that was twelve years ago and most viewers are more savvy now to the flimsy trickster ways of overzealous studios and marketing execs. The latest entry into the genre, "Apollo 18" is clearly fictional despite claims to the contrary, but it doesn't matter. A willing audience member's suspension of disbelief can go a long way in creating the necessary sense of reality as long as the performances are natural and the filmmaking itself free of obvious artifice. As directed by Gonzalo López-Gallego, "Apollo 18" gets this right the majority of the time. The limited cast of characters are too slimly drawn for their fates to be cared very deeply about, but viewed purely as a "what-if?" record of a dirty secret within America's history, it's worth a few honest chills.

It is well-noted that NASA cancelled Apollo 18's planned 1974 lunar mission, but what if that was all part of a big national cover-up? What if a trio of astronauts did set off on the voyage after all, the victims of a larger conspiracy that firmly put the kibosh on anyone ever returning to the moon? Culled from eighty-four hours of raw footage and edited into a compact representation of events long kept hidden from the public, the film that follows spells the end of any doubts about life existing beyond our planet. With their colleague off piloting the orbiter at the stationed command post, the other two officers, Benjamin Anderson (Warren Christie) and Nathan Walker (Lloyd Owen), begin a routine two-day study of the moon's surface. After coming upon an abandoned Russian proton lander, the inside bloodied and the corpse of a cosmonaut lurking nearby in a dark crater, the men realize something very peculiar is going on. The moon, it turns out, might not be quite as desolate as originally thought.

"Apollo 18" is a slow burn, but one that assuredly raises anxiety and tension the further it presses on. The nuts and bolts of the screenplay by Cory Goodman (2011's "Priest") and Brian Miller are straightforward and workmanlike, but also effectively researched in their technical mumbo-jumbo. As protagonists, Ben and Nate get no more than a job title and a few references to family members they've left behind, so the picture's dramatic hold isn't as strong as it could be. Where director Gonzalo López-Gallego amends this drawback is in his spare, fierce grasp of fright-based catharsis. There are a couple early moments that prove too obvious—the first time another living organism is glimpsed, it is filmed in close-up with a spotlight calling unnecessary attention to it—but once the stakes are raised and Ben and Nate are put into grave danger, the suspense level takes off. Particularly, a handful of solid jolts are enough to keep a person on edge, the silences pulling one into a false state of calm with almost maniacal fortitude.

Standing on the gray, barren surface of the moon with the majesty of earth far off in the distance, one of the astronauts comments, "It makes you think, doesn't it?" A little more of this sort of existential rumination would have been a welcome counter to the baser scare tactics on display. Nevertheless, the grainy, roughshod camerawork does its best to live up to the authenticity of what's being seen. This is by no means a pretty-looking movie, nor should it be. Instead, the imagery serves to match the premise's claustrophobic aura. When Nate says at one point, "You look out these windows, and sometimes get the feeling something's looking back," it acts as a surprisingly chilling harbinger.

In "Apollo 18," what specifically is stalking these two lonesome astronauts isn't as important as the nagging feelings of disquiet that come with the fear of the unknown. Cautious curiosity turns to terror, then helplessness, as Ben faces the knowledge that he and Nate were used as guinea pigs for an operation that NASA and the Department of Defense aren't willing to be held accountable for. In what could very well be his final days alive, Ben is faced with a truth about the universe not many humans can attest to. Were the characters only developed with more than the broadest of strokes and keener ambition given to thematic relevance, perhaps this revelation could have held a more lasting impact. As is, "Apollo 18" is less concerned with depth and more about the strict skillfulness of capturing an increasingly queasy tone and mood. This is where it works.