The title - a composite of the names that Martha is called or calls herself - gives a clue to the central theme of this film from first-time director Sean Durkin.
Who exactly is this girl and why is she skipping out on her bucolic haven in Upstate New York?
Martha can run away - to sweet sister Lucy (Sarah Paulson) - but can she ever escape?
The memories of her time in the country glide in and out of her new reality, mesmerically conjured by Durkin. So she's swimming at Lucy's lake-side summerhouse but she's also with her faux-family, white limbs in black water, thrashing like an orgy.
Back in the cult, under the watchful eye of sly father-figure Patrick (a sinewy John Hawkes), misery is joy, privacy is the enemy and conscience is obtuse. Good and evil blur into one thing after another, unmeasured and unremarked, a potent, hazy mix that encourages mindlessness.
They all find serenity there, the girls, and make their subdued torment a featureless part of the pastoral idyll. Martha comes away imbued with its mantras - that to make something abnormal into something normal, it is first a rite and then a habit and then just a thing that happens.
Used to free love, she sidles into bed with Lucy and fractious hubby Ted (Hugh Dancy) as they have sex. She scorns their materialism but has no alternative except the fortune cookie philosophies of her charming abuser.
Elizabeth Olsen in her debut makes the fragmented film work. Open-faced yet hollow-eyed, she is bemused and bewildered, formless and muddled. She sweeps through, rarely emoting but always puzzling.
The dreamy, sinuous direction and the perverted sanctuaries of the farmhouse and summerhouse leaven the terror into its own kind of banality. Rarely does conflict break the glassy surface.
And therein lies a flaw in this otherwise consummate exercise in film-making. These mosaic pieces compile to make an exquisite character study but to not much end.
Martha needs to be filled with something new or different but she, nor the bizarrely incurious Lucy, know what that may be and no-one is in a hurry to find out.
As the final shot hangs, we are left lingering not with the possibilities of what might come for Martha but with the notion that her journey was not as interesting as the film would have us believe.
