PARK CITY - "Why is it that self-righteousness always goes hand-in-hand with resistance movements?" So asks Brit Marling's prematurely jaded intelligence agent in her investigation of a particularly precocious band of eco-terrorists in "The East," a slick, involving, somewhat uneven independent thriller that marks the writer-producer-star's second promising collaboration with director Zal Batmanglij.

Funny enough in itself, the question encapsulates much of what works in this high-concept, higher-gloss bid for mainstream attention from the team behind "Sound of My Voice": incorporating and accommodating a range of views, the politics are elastic in what threatens from a distance to be a dry, earnest slab of liberal issue-mongering. Perhaps chiefly a study of noble causes pursued by less-than-noble means -- and questioning how wide that chasm between , "The East" follows Batmanglij's previous film in portraying the infiltration of a cult-like underground organization with an undefined depth of influence.

So vivid as the basement-dwelling, only notionally human cult leader in "Voice," Marling here switches tack to play the intruding outsider -- though her script, once more co-written Batmanglij, allows audience mileage to vary as to whether she's our heroine or not. Either way, as Sarah, a star operative for a private intelligence firm hired to protect big-name corporate clients, she is our window into the world of The East, a creative, violent and, yes, extremely self-righteous group of anarchist environmental campaigners led with quiet authority by Benji (Alexander Skarsgård).

When Sarah is put on their trail by her sleek, serpentine boss (Patricia Clarkson on deliciously wily form), she wastes little time entering their ranks -- though upon discovering that The East, when not raising hell among big oil bigwigs, essentially function like an adult Montessori group, complete with sharing-is-caring induction rituals and New Age mutual bathing ceremonies, she could be forgiven for wishing she'd taken a little longer.

Theshe lands herself ritualistic otherness of these scenes makes for grandly compelling viewing, as do a series of tightly screwed suspense sequences detailing her undercover involvement in The East's outlandish operations: a mass act of champagne poisoning, in which the heedless manufacturers of a dangerous pharmaceutical are given a taste of their own medicine, would tickle Hitchcock with its old-school mechanics. (Halli Cauthery's score, with militaristic-sounding themes from Harry Gregson-Williams, is a pleasure throughout.)

For its first half, then, "The East" occupies the territory of high-class airport fiction, embellished with smart, non-didactic moral and political discussion points as Sarah inevitably finds herself seduced by the organization's ideals. Keeping The East interesting as a character ensemble is the range of views and perspectives presented within it: no surprise, then, that pressing from within for less destructive forms of protest earns Sarah vocal resentment in some quarters (notably from chief East hothead Izzy, snappily played by Ellen Page) and more sympathetic – positively doe-eyed – attention from Benji.

It's at this point that "The East," which has hitherto skated just on the right side of silliness, unravels to some extent. Sarah's previously impeccable decision-making goes inexplicably awry. It's hard to believe that a professional as accomplished in her field is Sarah would allow the romantic attentions of one highly inscrutable man -- or even a Norse god, in Skarsgård's case -- to jeopardize her personal or professional security to the extent that she does here.

Acing her most substantial lead role to date, Marling's a sufficiently deft, empathetic actress to knit these shifting motivations together, making her third-act behavior disappointing rather than disorientating, even as she lands herself with a curious, high-strung speech about food waste at a key dramatic crux. Provocative and sharply crafted to the end, successfully bridging its star and director's indie roots with their multiplex potential, "The East" maintains its intelligence, but arguably flexes it a little too eagerly. That's a luxurious quibble to have with any comparatively mainstream thriller, or indeed any female-driven entertainment, these days, particularly one ripe with sequel opportunities. Look to The West, everybody.