How do you dramatize the plight of the throngs of middle-class Americans whose once-comfortable lives crashed during the last recession? How do you get their pain, and anger, through to an audience benumbed by home foreclosures and job-loss statistics, and by 3-minute TV human-interest stories that barely graze the surface of (or the reasons for) this widespread suffering?

ACT Theatre’s taut Seattle premiere of Laura Marks’ 90-minute Off Broadway play “Bethany” begins by giving us a female protagonist that nearly anyone can relate to.

Crystal (the emotively ambidextrous Emily Chisholm) is a fresh-faced, pleasantly perky young car saleswoman struggling mightily to keep her life from total disintegration.

She’s lost her house. She’s about to lose her job at a closing Saturn dealership. But the worst loss is of her daughter Bethany, who has been placed in foster care until Crystal can score them a decent home.

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Crystal’s desperate straits are not far-fetched, and they are etched in some telling detail here. But Marks’ play, which takes sharp turns into inky-dark territory, is implausible on several counts as a fictional documentary.

Would most women, no matter how hard up, squat in a foreclosed house inhabited by a clearly disturbed homeless man with a hair-trigger temper (Gary, portrayed with laudable nuance by Darragh Kennan)?

Would a social worker (Cynthia Jones) not check in with Crystal’s employer and her landlord, when assessing her fitness to reclaim Bethany?

Would such a hardworking young person have no family or friends or ex-partner to speak of, or turn to?

These and other gaps in credibility would trouble a production of “Bethany” aiming for realism. But director John Langs and his team wisely instill a sense of the surreal and the foreboding into the action from the get-go. And when the carefully laid tension peaks and sends Crystal into a Darwinian spiral, we’re primed for it.

Brendan Patrick Hogan’s canny sound design sets the mood even before the lights go up, with a skittering, eerie score that returns to haunt you. (It sounds, aptly, rather like a street musician’s furious drumming on plastic pails.)

As Crystal’s unwelcome roommate, Kennan turns what could be another scuzzy bogey man into a damaged soul whose anti-establishment rants are garbled with both sense and nonsense. He is paranoid, unwashed and anti-social. But his dire warnings of social disintegration and his survivalist’s credo are not foreign to Crystal’s dilemma, as her civilized mien begins to crack under extreme pressure.

A counterpoint to his voice of doom is the blind optimism of Charlie (Richard Ziman), a “transformational motivation speaker” whose purchase of a luxury car would plump Crystal’s bank account and ease her stress. Played with edgy brio by Ziman, Charlie is a bluntly obvious symbol of the huckster dream-peddling endemic to American capitalism — and the fraudulence of that perverse think-yourself-rich fantasy.

Crystal isn’t buying his line. But the brutal force of the free market is stripping away her wholesomeness and moral convictions. As an important deadline bears down on her, she simply cannot afford ethical niceties any more. During a shrewd negotiation with Charlie’s wife (a spot-on Suzanne Bouchard), she becomes capable of what sounded so preposterous when Gary spouted it.

If you take it literally, “Bethany” gives devoted single moms under financial duress few options, none of them good. That’s why Langs’ interpretation of the piece as a kind of early Roman Polanski horror fable (“Rosemary’s Baby,” “Repulsion”) makes so much sense. In his use of strobes, choreography and that needling music, he makes Crystal’s story a cautionary fable, febrile and disturbing.

And Chisholm’s contribution is essential. Her transformations, physical and moral, are so incremental and persuasive you can’t turn away from Crystal — even when the system utterly fails her, and she strikes back with a hellish vengeance.

Misha Berson: