They’re not right anymore, the Bateses aren’t, not since the accident that left their daughter bedridden, trapped in her own head and babbling incoherently.

“Something has snapped inside of us, and things don’t fit together as they used to,” they tell each other, in the kind of lyrically inarticulate exchange only characters in British plays can manage. Mrs. Bates (Nancy Robinette), her life so circumscribed by her daughter’s incapacitation that she can’t even get out to the corner market, teeters on the verge of a nervous breakdown; Mr. Bates (Mitchell Hébert), so embittered by his child’s fate that he can barely stand the sight and sound of her, poisons himself and his relationships with the anger he’s bottled—distilled—inside. “I wish some thick, ugly Irish oik would come and blow us all up—especially you,” he says to Mrs. Bates early on, with a kind of weary hatefulness; it’s an oddly revelatory insult, laying bare in one observation the seething resentment and all-purpose racism that blacken everything he touches.

Lucky them: The devil has decided to drop by to help them put their rapidly disintegrating household back in order.

Actually, Dennis Potter (The Singing Detective, Pennies From Heaven) may have intended to leave at least a little question about who exactly Martin, the charismatic young con man who insinuates himself into the Bateses’ home and into their lives, is meant to be in this darkly funny, deliciously blasphemous play about the near-impossibility of entirely separating good from evil. (Originally a teleplay, Brimstone was banned by the BBC in 1976, then turned into a stage play and later a film starring Joan Plowright, Denholm Elliot, and Sting; the original TV version finally aired in Britain in 1987.)

But in the sharp-edged, sulfurous production by Woolly Mammoth Theatre Company, Christopher Lane’s Martin twitches at the merest hint of piety, director Tom Prewitt punches up a couple of the character’s diabolically clever lines, and sound designer Daniel Schrader conjures thunderclaps each time Martin mentions God, so by the time Mrs. Bates gets around to puzzling over why she smells “the tops of matches,” it’s fairly obvious to the audience that there’s a little more to Martin’s employment history than he’s letting on.

He seems, at first, the answer to Mrs. Bates’ prayers—thoughtful, attentive, not to mention handsome. Above all, he seems devoted to the unfortunate Pattie (Rhea Seehorn); he claims he’s an old boyfriend, even to have proposed to her once. The Bateses see in him precisely what they want—need—to find there: For Mrs. Bates, he’s a helpmate and an ally who bolsters her stubborn faith in Pattie’s eventual recovery, while for the ill-tempered man of the house, he’s a political bedfellow, a willing listener (perhaps an unsettlingly enthusiastic one) to xenophobic diatribes, and most seductively an establisher of order in the unsettled household. And why shouldn’t both of the Bateses be charmed? Martin’s a flatterer and a flirt, only too happy to make the beds, cook the dinner, feed the invalid, wash the dishes, and brew the tea so as to free the Bateses from their stifling routine and make their lives a little lighter—and while they’re away he’ll rifle through their dresser drawers and rape their helpless daughter.

Lane plays this obliging bastard with a carefully balanced mix of nasty and nice; it’s an unpleasantly appealing, entirely accomplished performance, even if it can’t quite overcome the odd disconnects that result from making the character’s origins so clear. (What use would Old Scratch have for the jewelry and cash Martin keeps looking for? And why would he, as Martin tells us he has, fail repeatedly at his con game before finally stumbling across the gullible Bateses? You’d think the devil would be a surer hand at deception.)

Robinette and Hébert give perilously stock character types a richness and dignity that’s surprising in such an unapologetically unpleasant play. Robinette’s capacity for quiet desperation has never served her better; Hébert’s choked emotionalism makes Bates more a human failure than an inhuman monster, even after Pattie’s transformative post-rape reawakening raises doubts about exactly what he was doing the night of her accident.

If James Kronzer’s queasy, claustrophobic prison of a living-room set seems atmospherically literal, the mildewy gray that creeps up the walls—and the nauseating yellow wallpaper, which begs speculation about Charlotte Perkins Gilman and encroaching madness—looks to be an apt metaphor for the encroaching mustiness and misery of the Bateses’ existence. And if the wash of light that covers Pattie upon her (almost Biblical) resurrection doesn’t entirely sweep the place clean—well, there are unanswered questions at the curtain call, aren’t there, and interesting ones, too.CP