Peter (Christopher Denham) and Lorna (Nicole Vicius) park in a garage. They are placed in another car, where they are taken to a nondescript suburban California house. They strip and thoroughly wash themselves. Clad from then on in only white hospital robes, they are loaded into another car and blindfolded. When those blindfolds come off, they find themselves in another unknown house. Marched down into a basement that locks from the outside, they are then faced with a final obligation courtesy of Klaus (Richard Wharton), a suspicious gentleman who requires that they complete the mirrored half of an elaborate handshake. And after that, things start to get strange.

This is the world of Sound of My Voice, director Zal Batmanglij’s debut feature and the second Fox Searchlight release written by and starring Brit Marling in the past year. (Last year’s insipid Another Earth was the first.) The film is a brilliantly subdued thriller, one that reduces even the “slow burn” to a stillness that’s far more haunting. Indeed, it’s hard not to compare this film to Martha Marcy May Marlene, but where that film introduced a series of mysteries that it had no real interest in exploring or answering, Voice doles out its information slowly and purposefully. At the core of the film’s cult is Maggie (Brit Marling), a charismatic and ethereally beautiful woman who possesses a ruthless coldness at her core.

Peter and Lorna have just as many secrets as Maggie, chief among them the fact that their involvement in Maggie’s cult is in service of a larger goal, that of a documentary the couple intends to make in secret exposing Maggie as a fraud. They fear her, and not unreasonably so; she’s charismatic enough to entrap her followers, and powerful enough to make them do virtually anything she would ask. As her secrets start coming to light, Peter and Lorna’s relationship is tested against their own personal frailties, which Maggie is more than willing to exploit to reach her own desired ends. Batmanglij’s style is perfectly non-showy; he keeps things uncomfortably intimate at all times, forcing the whole film into the tiny microcosm that for Peter, Lorna and their fellow followers slowly becomes their entire universe. As the tension begins to mount, and it becomes clear what’s expected of the new couple if they want to prove their loyalty, the film elicits an exhilarating feeling of anxiety, built and earned in tiny increments.

He’s benefitted by a trio of excellent performances. Denham is neurotic and wounded as Peter, whose perpetual sarcasm, scorn and evasive tactics are slowly worn down by the pressures of keeping their secret, and perhaps Maggie herself. As Lorna, Vicius has less to do but does it well; it’s revealed she’s an ex-debutante turned health nut, and she captures this impeccably, with a certain sense of entitlement masking the fact that she’s becoming increasingly afraid for her and Peter’s safety. The real star is Marling, though, who gives a steely, frightening performance that’s made all the more so by her soft appearance and demeanor. Her sense of purpose is undeniable (both in her performance and in the film’s perfectly pitched screenplay), and at the risk of using an unbearable bit of wordplay, it’s indeed her voice that gives Sound of My Voice such vivid power.