At first glance, Boston Marriage looks like a classic Edwardian drawing-room comedy concerning two well-heeled women, Anna and Claire, and their put-upon housemaid. Anna and Claire are engaged in a Boston marriage, a 19th-century euphemism for cohabitating women who may or may not have an intimate physical relationship. The action of Boston Marriage — which happens to be the only David Mamet work featuring an all-female cast — takes place on a single set, with no scene changes. The thin plot is advanced via linguistic gymnastics rather than physical movement, providing a unique challenge for the cast and director. Threshold Repertory’s upcoming production has a breakneck pace and a decidedly bitchy overtone that camouflages the heartfelt feelings lurking beneath the repartee.

“This is a hard play to get, in terms of language,” says Threshold Rep’s artistic director Pamela Galle, who also plays Anna. “We spent the first few rehearsals doing table readings, probably 40-plus hours of simply reading through the language and decoding it.”

Galle also says that while she finds the play hilariously funny, it took time for her to uncover the humor in the language. “I realized this is a human story and came to see how beautiful and rich the language is. It’s also funny. Humor is really the thrust of this play.”

As the play opens, the two ladies of the house converse amidst fainting couches, delicate occasional tables, and cups of tea — there’s even a reference to redecorating the room in “chintz.” Wait, is this really David Mamet, the classic guy-guy, locker-room language, rough and masculine playwright?

It’s only a few minutes into the first act when Claire (with an impeccably raised eyebrow provided by actress Haydn Haring) remarks to the older Anna that her emerald necklace may be a bit “excessive for the morning.” Within a few short moments, Anna reveals that the jewelry in question is a family heirloom from a male lover she has taken in an effort to provide financially for the household. The younger Claire then shares that she is “in love” — with a young girl — and goes so far as to ask Anna to allow her to use their shared home for a tryst with the object of her affection. Not too long after, “You whore!” shows up in the conversation.

That’s the quick-witted, ruthless language audiences may recognize from Mamet’s other works. But there’s a deeper, and deeply feminine, machination at work beneath the tough words in Boston Marriage. Plus, the play is full of funny lines, and that humor, biting as it is, serves to soften the characters and help the audience understand the insecurities and desires hiding beneath the insults and layers of petticoats.

“The women in the play have standard foibles, like being in love, feeling betrayed, being afraid of getting kicked out of their home,” says Galle.

These human afflictions provide the human story behind the language. As the women trade insults, apologize, throw barbed double entendres, and make witty, seemingly offhand comments, it gradually becomes apparent that they actually love each other.

Haydn Haring, who plays Claire, describes the play’s language as a “mouthful,” but says that she also found it an important clue to developing her character. Haring alludes to a “secret language” shared by Claire and Anna, one they have cultivated over years of friendship and which defines both them and their relationship. “I love the language they use with each other,” Haring says. “It’s what makes this story what it is.”

And it seems like Claire and Anna’s language rubbed off on Haring and Galle. Haring says, “You can sink your teeth into it. You can chew on the words,” while Galle describes the entire experience of the play as “a full meal.” This toothiness of language, while it proved challenging to translate to the stage, also makes the production a richer experience.

“The dialogue is so expressive,” says director Lon Bumgarner. “It says so much about what’s going on between the three people. It boggles me how beautiful it is.”

Bumgarner says he prefers to direct works that have something going on behind the surface dialogue. He can sometimes hear the author creeping in through the characters. “So each one sounds like different versions of the same person,” he says.

This play does not suffer that problem. It’s about “three completely separate individuals,” says Bumgarner, who, through his direction, tried to layer intentions and motivations on top of and beneath Mamet’s words, so audiences will be able to feel the “dissonance between what the characters are saying and what they really mean or want to say.”

There’s certainly dissonance in Boston Marriage, between what the characters say and what they mean, between reserved drawing-room behavior and the human passions hiding beneath, and between Anna and Claire’s selfish desires and their deep-down love for each other. It’s this complexity that makes this work a challenge for the production’s actresses and director, and that moves its action along at hyper-speed, even though it never leaves the drawing room.