As 1971 bestselling novel or 1973 smash pic, William Peter Blatty’s “The Exorcist” has always represented an ungainly amalgam of prolix theology and terrifying Grand Guignol. The Geffen’s updated stage adaptation clearly hopes helmer John Doyle’s theatricality will compensate for cinematic pea-soup vomit and a moppet’s spinning head, but his black magic never quite rises to the spine-chilling. Those not intensely interested in Blatty’s unified field theory of good and evil are likely to perceive this self-conscious religioso exercise as a case of bait-and-switch.

An unnervingly pretentious note is sounded at the get-go. Virginal Regan McNeil (20-ish Emily Yetter, believably adolescent) crumbles and spits out a holy wafer, and a cassocked Father Merrin (Richard Chamberlain) poses downstage to intone, “For anyone who doubts the existence of the devil as I once did, I have three words. Auschwitz. Cambodia. Somalia.”

That geopolitical name-dropping in questionable taste is delivered on a stage that designer Scott Pask surrounds with cathedral grillework as a giant crucifix hangs above; plainly, we’re not to expect much in the way of fun. Blatty’s on a sincere mission to proselytize his conception of God as guilt’s antidote to despair, but the sermonizing comes across as sententious and flat in this context. No one’s willing to allow us to figure out any moral lessons for ourselves.

“Agnes of God” scribe John Pielmeier trims to 95 minutes the narrative of Regan’s demonic possession as first noticed by her sassy actress mom (nice unmannered work from Brooke Shields).

Events transpire as readers and filmgoers will recall them. The girl’s weirdly aggressive behavior is untreatable by smug doctors (“It’s a lesion on her temporal lobe”) or clueless shrinks (“Her unconscious may give us some clue”). Then the mysterious death of whisky-sodden movie director Burke (an over-the-top Harry Groener) places matters into the shaky hands of Father Damien Karras, a caustic David Wilson Barnes staring down at his feet and muttering, “I’ve lost my faith.”

Karras and Merrin, main delivery points for Blatty’s messaging, are drastically underplayed by contrast with Jason Miller’s titanically anguished Karras and Max von Sydow’s haunted, soul-weary exorcist in the movie.

Barnes talks a good game out of the Graham Greene doubting-priest playbook, but he’s all shrugs and diffidence. Since his spiritual pain barely registers, his ultimate change of heart comes out of nowhere.

Chamberlain fares even worse, sauntering in periodically to describe encounters with evil informed by Blatty’s occult research (for readers of the novel, those are the pages you flipped past en route to the next outrageous set piece). His bland, amiable manner is so reminiscent of the narrator in “The Rocky Horror Picture Show,” you expect to learn combatting Beelzebub involves just a jump to the left and then a step to the right.

As for the stagecraft, Doyle takes as his cue Catholicism’s transformative nature (bread and wine becoming Christ’s body and blood). So the cast never leaves the stage, assuming multiple roles and collaborating on Satan’s vocal hijinks.

Religious props are variously used. A single table serves as altar, bed and examination gurney, and the incense-scented air is dense with murmured prayers, heavy breathing and John Tavener’s Enya-tinged crooning. (Actually, even minus Mike Oldfield’s iconic “Tubular Bells,” Dan Moses Schreier’s sound plot is the most satisfyingly creepy production element.)

There are a few jolts from Schreier’s sonic booms and Jane Cox’s expressionistic lighting flashes. Teller, silent member of magic team Penn & Teller, presumably consulted on levitation and bed-thumping, though the game Yetter’s gymnastic gyrations suggest coaching from Bela Karolyi. The climactic rite is disappointingly abrupt.

If “The Exorcist” moves on to Gotham as rumored, at least one element warrants attention. To leave Lucifer alone with Burke to reverse his head and toss him out the window, Pielmeier asks us to believe an $8 million-per-picture diva would not only insist on personally running out to fill a prescription but also demand her soused director’s babysitting services. Your average movie star has assistants aplenty for such dirty work. There’s no way in hell the devil could make her do it.

The Exorcist

Geffen Playhouse, Los Angeles; 522 seats; $87 top

  • Production: A Geffen Playhouse presentation of a play in one act by John Pielmeier. Directed by John Doyle.
  • Crew: Sets and costumes, Scott Pask; lighting, Jane Cox; sound, Dan Moses Schreier; music, John Tavener; creative consultant, Teller; production stage manager, Adam John Hunter. Opened, reviewed July 11, 2012. Runs through Aug. 12. Running time: 95 MIN.
  • Cast: Father Merrin - Richard Chamberlain Chris MacNeil - Brooke Shields Father Damien Karras - David Wilson Barnes Regan MacNeil - Emily Yetter Burke Dennings - Harry Groener With: Stephen Bogardus, Manoel Felciano, Tom Nelis, Roslyn Ruff.