If David Mamet knows one milieu, it’s the confidence game. He understands that people will do anything, from buying useless tracts of Florida swampland (“Glengarry Glen Ross”) to supporting a nonexistent war (“Wag the Dog”), as long as they’re asked properly.

But what if the con man inspires a complete lack of confidence? Does compassion or decency do anything to mitigate the whiff of flop sweat? The long-neglected Victorian dramatist Harley Granville Barker posed this question in his 1905 drama, “The Voysey Inheritance,” which Mr. Mamet has now tightened and tweaked to dynamic effect for the Atlantic Theatre.

Mr. Mamet surprised theatergoers in 1999 with his fine-boned screen adaptation of Terence Rattigan’s “The Winslow Boy,” in which a father scrambles to clear his son’s name, and the son proves an equally dab hand when it comes to returning the filial favor. This time it’s the son’s turn to try salvaging the reputation of his pilfering father, and while Mr. Mamet has made no attempt to mold Barker’s well-parsed locutions to his own terser rhythms, he and director David Warren have crafted a tense, well-mannered morality play in which intentions and impressions rarely line up.

The young solicitor Edward (Michael Stuhlbarg), who has a decent head for business but none for salesmanship, has uncovered evidence that his avuncular, poised father (Fritz Weaver) has been using his clients’ private accounts to subsidize the family’s lavish lifestyle. (This is something of a Voysey tradition: We’re told that the father inherited the cooked books from his father.) “The firm’s funds were just a lucky bag into which we dipped,” Edward explains to his siblings.

When Edward begrudgingly assumes control of the firm (Mr. Weaver appears only in the first scene), he has the option of either blowing the whistle, thereby ruining the family, or attempting to minimize the damage from within. The irony here is that the very qualities that make Edward so courageous — his unwillingness to obscure or even sugarcoat the truth, his inability to live up to his opulent surroundings — are what prevent him from earning the trust needed to perpetuate his father’s scheme, even when doing so is in his clients’ interest.

Guilt over the family’s misdeeds hangs over Edward until he develops a fiduciary death wish, making him even more suspect: One investor interprets Edward’s sangfroid at the prospect of ruin as evidence of some sort of triplecross.

While Barker shifted the action between a London office and the library of the Voysey estate in nearby Chislehurst, Mr. Mamet has confined his adaptation to the latter location. This has the dual effect of conflating the family’s luxury with its sins while also allowing Mr. Warren to make do with just one set. (And what a set it is: Derek McLane has devoted every square inch of wall space to gilded portraits and Romantic landscapes, and armchairs don’t get more inviting than the pair nestled by the fireplace.)

Mr. Mamet has also added a new wrinkle to the final complications involving Edward’s protracted courtship of Alice Maitland (a fetching Samantha Soule) and boosted the role of the complicit office clerk, Peacey (Steven Goldstein). Upon learning that the business will adhere to a stricter code, one that no longer includes hush money, Mr. Mamet’s Peacey engages Edward in a more nuanced ethical discussion:

EDWARD: You’re worse than a thief. You’re content that others should steal for you.

PEACEY: And who isn’t?

Well, Edward isn’t, which is his whole problem. In fact, father and son are so completely opposite — in appearance, in vocal timbre, in physical ease — that a cloud of suspicion initially hangs over Mr. Warren’s casting of Messrs. Weaver and Stuhlbarg. Both are superb — the aquiline Mr. Weaver’s suavity proves a seductive foil to Mr. Stuhlbarg’s pinched desperation — but it’s hard to believe the two share any DNA.

When Act II begins, however, Edward has had more than a year to grow accustomed to his slippery situation, and he shows the tiniest glimpses of the elder Voysey’s malevolent charm. Coupling this “evolution” with a sense of the physical toll it’s taking (restful nights would appear to be in short supply for Edward), Mr. Stuhlbarg paints a vivid picture of a man who is both condemned and redeemed by his own decency.

Mr. Mamet’s cuts have reduced the roles of much of the supporting cast, but most of the actors put their own stamp on the parts anyway. C.J. Wilson blusters effectively as Edward’s stuffed-shirt brother, Mr. Goldstein finds intriguing depths to the conniving Peacey, and Peter Maloney is memorably dyspeptic as an investor who stands to lose a great deal.

“The more able a man is, the less the word ‘honesty’ bothers him,” intones another of Edward’s brothers upon learning of the family’s ignoble inheritance. “And father was an able man.” That ability kept Edward’s father above the law for decades, and “The Voysey Inheritance” shows that crime can indeed pay — if you’re good at it. And if you’re just good? Harley Granville Barker, with a little help from his gimlet-eyed new collaborator, offers a few inventive answers to that question as well.

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