I don't know in what church actor Shawn Hamilton (a.k.a. associate pastor Joshua) will be preaching after he leaves the megachurch depicted in Lucas Hnath's The Christians, but I'll be there in my Sunday best as one of his new congregants. His Joshua has passion, conviction and fervor enough for a pulpit full of Billy Grahams and Joel Olsteens.

Although only one out of five characters in Hnath's catholic dissection of Christianity – and not the play's primary role – Hamilton shakes the rafters, raises the roof and scares the bejesus out of this woeful sinner. If the rapture's coming, I want to be on his side. Pastor Joshua is all hellfire and brimstone and, truth be told, I may not believe anything he believes, but Hamilton's so almighty convincing that it's hard to disagree with him, and awfully hard not to admire him. He's so damned authentic, his confrontation scene burns with inner intensity. He's got fire inside. Everybody else has embers.

A current darling of the off-Broadway crowd (Isaac's Eye; A Public Reading of an Unproduced Screenplay About the Death of Walt Disney; Red Speedo, which premiered last month in New York; and Hillary and Clinton, which premiered last week in Chicago), young playwright Hnath (pronounced “nayth”) knows his Bible, and he turns his play into a meta-sermon taking place in a sparkling-clean megachurch, like our own Lakewood down by Greenway Plaza. A celestial harmony of blond wood, potted shrubbery, azure-tinted rugs and cushions, James Youmans's set design is plummy neo-ecumenical. The stained glass is abstract, no patriarchs or representations of Bible stories. You may not even realize you're in a church except for the mammoth two-story back-lit cross: Dan Flavin goes to heaven. And then there's the choir, who proceed into the bleachers as the lights go down, and rock out to a Top-40 gospel number to get us in the Sunday mood.

Although the play is set in the “21st century,” microphones – and their sinuous cords – play as important a role as any actor. All five characters hold their own mikes (no wireless in these modern churches?) and maneuver those tortuous cords like Judy Garland at the Palace. The idea of witnessing is strong, like some sort of public confession, as inner and outer thoughts are openly projected to all. It's a gimmick, but somehow it works in this churchly venue cum reality show. Even stage directions are spoken aloud by the main character, pastor Paul (Richard Thieriot), who prods the discussion with mundane “he said”s and “then she said”s. It's artificial, to say the least, but surprisingly good theater, too. When did you ever see a play performed entirely by actors talking into microphones?

Paul begins his sermon. And that's when all hell breaks loose. Paul has had a conversion, an epiphany. Is he a contemporary St. Paul on the road to Damascus? Maybe, maybe not. There are layers, if not especially deep ones, in Hnath's own sermon.

A missionary in war-torn Africa has told Paul about a teenage boy who ran into a burning hut to save his little sister. The boy died. Because he wasn't a Christian, his soul naturally went to Hell. Paul is aghast at this callousness. Surely this isn't the message of God. God is goodness and mercy. Heaven will be filled with everyone, not only Christians. And that is what he preaches today. There is no Hell!

The four other characters, who stand in for clergy (pastor Joshua), laity (Jenny, Melissa Pritchett), business interests (Elder Jay, Jeffrey Bean) and personal life (wife Elizabeth, Emily Trask), try to make sense out of Paul's blasphemy. He has “cracked the bedrock” of the church, as he preached in his opening remarks. If there's no hell, they will argue with Paul in individual scenes, what's the use of Christianity? If we all go to heaven, no matter how heinous we've been on earth, why bother being good at all? What happens to shame? To guilt? To charity?

Paul rebuts the charges like any decent professor of comparative religion. The concept of hell's been mistranslated. The historical antecedent was Jerusalem's garbage dump, where all criminals' bodies were dumped after execution. It was an ancient metaphor. He's clever, no doubt about it, but offense is swiftly taken. Incensed, Joshua demands a vote by the members. Who is on the Lord's side? Joshua loses the battle, and in high dudgeon walks out, losing his job. Elder Jay tries reason as the coffers dry up. If the basic tenets of the church mean nothing, what's to keep the congregants filling the pews and, referencing the bottom line, giving money? Full of righteousness, Paul dismisses him too.

Working-class Jenny, a surrogate for us, it seems, strikes closer to home. She steps out of the choir to read her disapproval letter, although she doesn't really want to. Would Pastor Paul have given his sermon before the church had paid off its debts? If someone murdered her son, would both of them get into heaven? For a kicker, she asks about Hitler. Will he be there? Taken aback, Paul sidesteps but none too agilely. He has to say, Yes, he too will be there. But Heaven is not what we can imagine; it's not for us to judge. We cannot comprehend what it is. Pritchett handles Jenny with consummate skill, giving perhaps her best performance in many seasons. Simple and direct, her Jenny is pure of spirit, then terribly broken-hearted by Paul's doctrinaire intransigence.

One by one, they walk out of the church, out on Paul, leaving behind only wife Elizabeth sitting on the dais as ally, but she, too, confronts him. No longer the little lady in her crisp suit, she feels betrayed and abandoned. Betrayal looks great on Trask. Why didn't he confide in her before making such a public, if heartfelt, declaration? Where is his trust in her? What else hasn't he told her? What else is he hiding?

The weak link is Thieriot, whose conversion reads more smug than true. Paul has taken a penny-ante storefront and turned it into “thousands of seats, classrooms for Sunday school, a baptismal font as big as a swimming pool.” Which is all fine, but we don't believe Thieriot did it. His Paul doesn't burn with any conviction whatever; he hardly smolders. Complacent and slightly smarmy, he's a charismatic preacher without charisma. His faith has feet of clay.

Hnath doesn't play favorites and doesn't tell us how to react since all opinions are treated with equal reverence. Director Gregory Boyd keeps the equilibrium nicely balanced. There are no villains, no heroes. Everything's open-ended, fit for a lively Sunday school symposium. The ending is appropriately ambiguous. As a play of ideas, The Christians leaves us with much to discuss, if little actual drama. Whether you're going to Hell or always wanted to play the harp, there's plenty to think about – you've got an eternity.

The Christians continues through May 15 at the Alley Theatre, 615 Texas. For information, call 713-220-5700 or visit alleytheatre.org. $26-$67.