Martha (Elizabeth Olsen) flees from a commune in the Catskills one morning and phones her sister Lucy (Sarah Paulson), whom she hasn’t seen in two years. Lucy drives her out to the lake house that she and high-achieving husband Ted (Hugh Dancy) are vacationing in. But any hope of reconciliation, or explanation of what the hell Martha was up to in the years she went missing, are frustrated by her clipped, evasive replies to any questions. Worse, something has changed in her, it’s like she has unlearned normal human behaviour somewhere along the way. And while tensions grow in the uptight lake house we see flashbacks to the life Martha has fled, a cultish, coercive, sexualised world of disturbing mind games, which may not be willing to let her go…

Sean Durkin’s debut is a creepy, tense and ambiguous piece of work. Camera sound and editing combine to admirable effect, and Olson is a bit of a revelation as Martha, in a nuanced study of fear and concealment. The slowly emerging details of the Mansonesque commune convince. The acoustic guitars, encounter group smiles and counterintuitive psychobabble (‘death is pure love’) spouted by indie favourite John Hawkes as the charismatic, controlling leader never trip over the line into the lurid clichés they could be in clumsier hands. Durkin makes smart choices about what to leave out of his story; the flashbacks detail the emotional and personal moments of life in the Catskills, but we don’t know what the cult’s religious or political aims (if any) were, and have to fill in the gaps. We wonder whether Lucy and Ted are in real danger, to what extent Martha has ‘drunk the Kool Aid’, and what she is capable of. But whether all this impressively sustained threatening atmosphere pays off to anyone’s satisfaction will, I suspect, be the cause of much argument.

Mark Stafford