WELLFLEET -- ''No. No. No." Conflict being the heart of drama, isn't that a terrific way to start a play? Corinne (Laura Esterman), a gin-steeped widow, is fending off a home invasion of sorts: Her late husband made a deathbed decision to will their house to her born-again stepdaughter, Rena (Tanya Clarke), who has just now shown up with her priggish minister spouse (Mark Rosenthal) to claim the cluttered old homestead. Corinne can stay on if she agrees to behave -- that is, quit drinking and find succor in Jesus instead. Three seconds into ''Mercy on the Doorstep," and playwright Gip Hoppe -- a cofounder of Wellfleet Harbor Actors Theater -- has set in motion a drama that is not only emotionally gripping but probes timely and important themes.
You can tell from the string of invectives that accompany the family reunion that the compulsory conversion won't go smoothly. The ideological battle of wills takes a number of surprising plot turns. Porn plays a role (Corinne's late husband ran a store purveying vintage comic books and skin flicks), and it's the one aspect that seems a bit off, or at least under-explored: Wouldn't a woman of Corinne's vintage (she's 50) and liberal bent have had some feminist qualms about the exploitation that the industry entails? Brushing that question aside, dad's little hobby shop provides Hoppe with the impetus to make up some hilarious X-rated titles, and a means to heat up the battle -- not just between Corinne and her sanctimonious captors, but between the members of the crusading couple.
All the characters have depth and each comes with a compelling back story: Corinne's devotion to her late husband (for whom her self-appointed role was good-time girl) seems genuine, as does Rena's relief at having transcended -- let alone survived -- her own stint as a godless party animal (''You were a pistol," Corinne reminisces fondly). Mark's childhood may have been a fundamentalist cliche, but you can see his struggle to humanize the legacy he has decided to embrace. All three are decent people at heart, even if their friction sets off sparks -- and cascades of laughter. Hoppe has achieved that rare amalgam, a comic drama that entertains even as it stimulates debate.
Red state, blue state; this play ought to be required viewing in both. The smarter regional theaters, not to mention New York's sophisticated fringe, should be lining up to stage it. They're unlikely, though, to surpass the perfect gritty realism of this playwright-directed production (Dan Joy's set is, as always, a complex and clever micro-universe), or to convene as ideal a cast. Rosenthal skillfully physicalizes Mark's internal torment, and Clarke, while retaining traces of the bad girl Rena once was, manages to rouse sympathy for the better person she's trying to become. Esterman is slyly brilliant as Corinne, alternately corrosive and tender. You feel for her and through her, and pray -- one way or another -- that she manages to retain her smart, feisty soul.