LOS ANGELES - A social-conscience espionage film that has actually thought about its "eco-terrorism" themes beyond figuring out how to mine them for suspense, "The East" sends a straight-laced overachiever undercover with a violent eco-vigilante group.

Zal Batmanglij and cowriter/star Brit Marling deliver a consistently tense, morally alert story that has plenty of box-office appeal.

Marling plays Sarah, a former FBI agent now seeking her fortune in the private sector.

Her first assignment for Hiller/Brood, a secretive company providing undercover risk assessments for multinational corporations, requires her to infiltrate a new anarchist group, The East, which has targeted polluters in a series of let-the-punishment-fit-the-crime "jams."

Telling her patient boyfriend (Jason Ritter) she's off to Dubai for business, Sarah actually hits the streets not far from her Washington, D.C., home - getting grubby with freegans and hobos while watching for someone whose political rants sound likely to produce action.

After an enjoyable bit of improvised role-playing, she winds up at the burned-up mansion The East calls home.

The group looks a bit like a cult, especially given the shaggy, Jesus-like appearance of head strategist Benji (Alexander Skarsgard), but is more of a democracy than it seems.

Members like Doc (Toby Kebbell) and Izzy (Ellen Page) offer villains from their own pasts - a reckless drug manufacturer, say, whose wares injured loved ones - and together they decide how to get close enough to do that company well-publicized harm.

The tidy paybacks will appeal to many viewers: Who hasn't thought execs who knowingly pollute waterways should have to bathe in their own slurry?

But putting a secret agent in the middle of their execution allows us to live the fantasy and question its justice simultaneously.

Sarah will inevitably be changed by this group. But will it be in the expected, manageable way - as her shark-like boss (Patricia Clarkson) warns, some sympathy is inevitable when you devote every waking moment to earning someone's trust - or will she go rogue?

The actors bringing this band of anarchists to life project enough wounded, uncertain self-righteousness to distance them from the generic zealots more often seen in this kind of tale, and Marling, working behind a couple of layers of role-playing, keeps audiences guessing about what Sarah actually believes.

Batmanglij balances emotional tension with practical danger nicely, a must in a story whose activist protagonists can make no distinction between the personal and the political. (By John DeFore/The Hollywood Reporter)