Maybe it’s good that it’s hard to realistically depict atrocity on stage, but that difficulty gets Sofi Oksanen’s “Purge” off to a rocky start. Soviet thugs terrorize women in a manner familiar from exploitative movies: rifle barrel sliding down blouse, with worse to come. Hard to watch, harder to act in a way that does justice to such agonies as are actually happening around the world.

Lynn Nottage’s widely produced “Ruined” (lately at Arena Stage) vividly evokes the rampant rape culture in the Congo; the Finnish-Estonian Oksanen takes similar aim at the plight of women in Estonia under Soviet and Russian domination. But as Oksanen’s script toggles between frosty Soviet tyranny in 1947 and the gangster-style hazards of early 1990s Russian control, the tang of a bad action picture is hard to shake.

Maybe it’s the heavy accents of malevolent mooks in track suits — again, tricky to render compellingly onstage — but Scena Theatre’s production in the intimate H Street Playhouse is hard to take seriously until it settles into more nuanced patterns of intimidation and fear. Saving the day in director Robert McNamara’s staging are three actresses delivering near-heroic performances.

Colleen Delany scales the most treacherous peaks of “Purge.” Delany, a gruesome sight in a mud-caked miniskirt with her lipstick smeared like clown makeup, has the role of Zara, an escaped sex slave. The show opens with Zara at the pinnacle of her trauma, and it takes an actress as fierce and intelligent as Delany to adequately navigate the early hysterics (and, later, to snarl threats while wielding a hatchet).

Far more compelling are Zara’s subtle, almost animalistic flickers of suspicion. You can sense the character’s sharp ears and racing mind as the hyper-alert Zara listens to the personal history of Old Aliide, whose iron indomitability registers as a terribly broad stereotype.

This tough bird is played with zesty defiance by Kerry Waters, her chin raised to I-dare-you levels. Old Aliide has a story to tell, all right, and we see it unfold in the 1947 sequences, with Irina Koval as a wily, younger Aliide, who makes devil’s bargains to survive in Soviet-controlled Estonia.

Koval is Delany’s match for jangled nerves and furtiveness in her well-judged scenes with Eric Lucas (who nicely underplays his part as the Soviet functionary Aliide sleeps with, while the man she loves hides in the basement). This is the play’s strength — showing the rich, awful layers of deception required to live under oppression .

The weakness is in the wild swings between drawn-out plotting and in-your-face violence that’s simply not convincing. In “Purge” the little moments soar; the big ones make you squirm.

Pressley is a freelance writer.

Purge

by Sofi Oksanen. Directed by Robert McNamara. Set, Michael C. Stepowany; lights, Marianne Meadows; costumes, Alisa Mandel; sound/video, Erik Trester. With Stas Wronka, Armand Simoni and Lee Ordeman. About two hours and 10 minutes. Through July 3 at the H Street Playhouse, 1365 H St. NE. Call 703-683-2824 or visit www.scenatheater.org.