Utah's Sundance Film Festival is renowned for turning small, weird films into mainstream hits, from Reservoir Dogs to Little Miss Sunshine. Writer-director Sean Durkin's debut Martha Marcy May Marlene (this reviewer is tempted to abbreviate this to MaMaMaMa) garnered glowing reviews when it premiered at the 2011 festival. A year later the indie hype-parade arrives in Cambridge alongside star-studded and heavily-marketed outings like War Horse and Coriolanus. So why should we care?

The film's mouthful of a title goes some way to breaking down its plot. Martha, played brilliantly by Elizabeth Olsen (yes, sister of Mary-Kate and Ashley), disappears for two years after falling into a cult-ish commune in upstate New York. Renamed Marcy May by enigmatic leader Patrick (John Hawkes), she eventually escapes and is re-united with her sister and her yuppie husband. I hesitate to reveal the meaning of the last name 'Marlene', as much of the joy of Durkin's film derives from the murky fashion in which the story progresses, the audience buffeted by the blur between Martha's dreams and memories.

2011 has been a bumper year for mentally unstable protagonists (see: Melancholia, Take Shelter) and Martha Marcy May Marlene adds a refreshingly low-fi feel to the assembly. The film's true secret weapon is the marvellous John Hawkes, who, besides looking unnervingly like a cartoon devil, makes Patrick realistically charismatic but with a palpable sense of terror bubbling near the surface. Hawkes gave a similarly show-stopping turn in 2010's Winter's Bone and I would bet a St John's May Ball ticket on him becoming a huge name in the coming years.

Martha is by no means a perfect film; it elaborates on its themes a little too pointedly at times, and Durkin's hazy framing of Olsen's body occasionally verges on American Apparel-ad territory. Yet the film's success is turning what sounds like a sensationalist headline, 'Beautiful girl escapes from abusive cult', into a thoughtful character study. It always feels like Durkin's inner exploitation film is just out of reach of the frame and when the true moments of horror do peak out, they are appropriately difficult to watch. Martha's ending will delight some and infuriate others, but the gamble is absolutely worth the price of admission. Come for the terrific writing and acting; stay for the argument in the pub afterwards.