A couple attempts to infiltrate a potentially dangerous (they insist) religious cult in order to expose it in a documentary film. The cult is headed up by Maggie (Brit Marling, who also cowrote), who claims to be a time-traveler sent here to shepherd us through an impending apocalypse. Is she a fraud or the real thing? That Sound of My Voice ultimately refuses to answer this question seems symptomatic of a larger failure to carry its concepts to any conclusion, let alone a logical one.

Peter (Christopher Denham) hides behind a facade of cold logic, while his girlfriend Lorna (Nicole Vicius) is a Hollywood heiress and ex-addict. They hope that busting the cult open will give their lives direction. Yet what little we uncover about our protagonists we learn from voice-over narration, while they mostly make unmotivated and, frankly, stupid decisions simply because the script deems it necessary or needs to stall for time. Rational Peter begins to doubt himself after a cold reading that Maggie could have cribbed from Miss Cleo. Lorna barely blinks when another cultist takes her out to the woods for an impromptu "shooting lesson."

Director Zal Batmanglij gets a lot of mileage out of the cult's sinister unfurnished basement headquarters, even with the stock microbudget handheld video, and Marling is a convincingly enigmatic but confident anchor. Still, you know this is all heading for some sort of twist, and by the time the rug (such as it is) gets pulled, the audience is left with an idea that hasn't developed into a story, ending exactly at what should probably be the first-act break. Intentional ambiguity is one thing, but here it seems like a crutch for filmmakers who can't follow through. Sound of My Voice is two-thirds of a movie—or secretly a dark comedy about two morons.