Her real name is Martha Marlene, but for the last couple years she has gone by Marcy May, a moniker that Patrick (John Hawkes) says suits her. With wandering souls and few concrete prospects, Martha (Elizabeth Olsen) and best friend Zoe (Louisa Krause) were welcomed into the fold of a patriarchal commune, existing off the grid in Upstate New York ever since. Now, having rustled up the courage to escape, Martha has been taken in by her older sister Lucy (Sarah Paulson) and husband Ted (Hugh Dancy). Staying at their tranquil lake house three hours away in Connecticut, Martha is understandably paranoid that she might still be found. Although she has not been forthcoming about where she's been, Lucy quickly realizes that Martha is not the same person she was when they last saw each other.

Sean Durkin won the Directing Award at the 2011 Sundance Film Festival for "Martha Marcy May Marlene," his commanding feature debut adapted from his 2010 short film "Mary Last Seen." The film's narrative is meticulous and controlled, weaving back and forth through time, flashbacks serving to inform what became of Martha while uncovering the events that led to her decision to try and break free from Patrick's clutches. This storytelling framework adds to one's intrigue and involvement as the commune—for all intents and purposes, a cult—grows ever more twisted and malicious, but Durkin's screenplay holds back from reaching a catharsis. Thus, the resulting finished picture is of two minds. On the one hand, it's certainly a fascinating look at the transformative effects of brainwashing and the internal struggle to be true to one's self. On the other hand, Martha's decision to never come clean to her sister as the people she has run away from may or may not be closing in means that there is little payoff and not much of an arc for Martha to face by the end. Aside from sending out the obvious message that cults are bad and dangerous, Durkin doesn't appear to have a deeper point.

Without resorting to obvious tactics of the horror persuasion, the film builds a sense of unmistakable disquiet, Martha's experiences approached with a blunt matter-of-factness. Things are off-kilter from the start, the way the women prepare food for the men, and then must wait until they are finished to also eat. Growing crops out back, their plan is to do away with any monetary need and live off the land. A so-called "cleansing" consists of each new woman getting drugged with a roofie and subsequently raped. Having gotten used to her place among the faction, Martha is told that she is "a teacher and a leader," chosen to welcome their latest female member, Sarah (Julia Garner), and show her the ropes before spiking her cleansing drink. This criminal rite of passage is the same one that happened to her, and what must happen to all the women after her. Now staying with Lucy and Ted, she hopes to put that life—one that grows much darker than what has already been revealed—behind her. What is not so easy, though, is letting go of Patrick's influence and the skewed ideas she's been indoctrinated with.

Whether or not this firmly spirited indie becomes a breakout success, the one element destined to be remembered is the strikingly complex performance of newcomer Elizabeth Olsen. Three years younger than big sisters Mary-Kate and Ashley, Olsen has tore out of the gate with a lead role superior to any that her multimillionaire siblings can attest to. There is no artifice or vanity in what she has done here, just a natural, layered, frequently breathtaking ability to slide into the skin of Martha. Sarah Paulson (2008's "The Spirit") is quite good in her own right as elder sister Lucy, her relationship with her sister a war between true empathetic concern and bitter contempt, while John Hawkes (2010's "Winter's Bone") is memorably assured and slimy as insincere, opportunistic cult leader Patrick. This is Olsen's picture all the way, though; she is such the captivating centerpiece that everyone else should feel lucky to be in her orbit.

The intentionally ambiguous last shot of "Martha Marcy May Marlene" will likely be a subject of debate for some time to come. Like Martha herself, it's enigmatic, and yet the lasting impression it sends out is unmistakable: no matter where she goes in life, she will forever be looking behind her back in fear at who might be there. At once frustrating and unforgettable, the ending is one that won't soon for forgotten. It also, unfortunately, concludes a story that doesn't feel finished or seem to live up to its potential. Without Martha willing to open up about what has happened, the emotional distance between herself and Lucy remains and any hope of moving forward is left hanging. As it turns out, physically fleeing her circumstances was only the beginning of the fight she has in front of her.