From the number of trained pigeons in a vaudeville act to the circumstances leading up to a central act of violence, the sumptuously written monologues that make up Brian Friel’s “Faith Healer” undermine and contradict one another in ways big and small. Mr. Friel’s minor masterpiece of 1979, which adds an ominous undercurrent of violence to his usual strains of Chekhovian discontent, finds rich veins of longing as it explores the inherent slipperiness of truth.

Unfortunately, director Jonathan Kent and two-thirds of his cast – a typically brooding Ralph Fiennes and an atypically brassy Cherry Jones – have taken this uncertainty as a cue to belabor every potentially meaningful filigree, resulting in a dismayingly leaden revival of a play that deserves better.

Even when the writing promises to transform its scruffy title character into a haunted icon of self-flagellation – and “Faith Healer” contains some of Mr. Friel’s sharpest, most unsparing prose – Mr. Kent’s glacial tempo yanks script and performers alike into a morass of drawn-out pauses and mannered orations. The flesh here is all too willing, and so the spirit is weak. Not even a late dose of character-actor heroics by Ian McDiarmid can resuscitate the oppressive goings-on.

The three characters, who never share the stage, are: Frank Hardy (Mr. Fiennes), a moody traveling evangelist; Grace (Ms. Jones), Frank’s long-suffering wife and nursemaid; and Teddy (Mr. McDiarmid), his irrepressible Cockney manager. The trio drive around Scotland and Wales, attracting a small but steady stream of “the crippled and the blind and the disfigured and the deaf and the barren,” as Frank describes them.

Judging from Frank’s threadbare clothes and anxious smile, business could be better on the faith-healing front. He succeeds in his ministrations just often enough to keep himself in a drunken state of anguish over his gifts: “Could my healing be effected without faith? But faith in what? – in me? – in the possibility? – faith in faith? And is the power diminishing?”

These concerns permeate the trio’s various troubles, both minor (constant money woes, a rickety van) and major (a stillborn child, the alcoholism that either parallels or precipitates Frank’s fading abilities). While the particulars vary significantly from monologue to monologue, things clearly come to a head during a long-delayed return to Ireland, where they encounter a rowdy wedding party at that Ballybeg pub. It quickly becomes apparent that, while the details may never be known, Frank’s crisis of conscience will reach a breaking point this evening.

The four monologues – Frank concludes “Faith Healer” with a second, shorter speech – are limpid, painterly chunks of writing, as Mr. Friel moves from Frank’s haunted musings to Grace’s spare reminiscences to Teddy’s huckster blarney and back again. But they run the risk of curdling if they’re treated too reverently, which is exactly what happens here.

Of the three performers, only Mr. Fiennes is given free rein of Jonathan Fensom’s bare, vaguely rustic set. (Poor Ms. Jones has been consigned to a chair for her entire monologue.) Frank stands inches from the lip of the stage, scuttles back to the farthest wall, and roams from side to side. And Mr. Fiennes supplies a comparable array of acting tools to fill the space: Cocking one hand on his hip, grinning nervously as if out of habit, assuming a broken posture, his Frank is still capable of presenting the outward appearance of a showman, but just barely.

Ms. Jones’s jittery take on the fragile Grace may be her loosest, earthiest performance in years, but her sedentary blocking forces her to rely too heavily on vocal histrionics and overemphatic body language. She does, however, make a convincingly inexperienced smoker, lunging at each puff out of rhythm with the cadences of her speeches. And while both find their share of compelling moments – Frank’s defensive anger at his damaged supplicants, Grace’s spare account of a tiny grave in northern Scotland – they’re also surprisingly careless with their accents, with a touch of Ms. Jones’s Bronx-based mother superior from “Doubt” even slipping in at one point.

The real miracle worker in this production is Mr. McDiarmid, a London stage veteran best known in America for his villainous appearances in the “Star Wars” movies. Like Bradley Cooper, who stole “Three Days of Rain” out from under Julia Roberts and Paul Rudd, Mr. McDiarmid comes in last and is asked to handle most of the humor. And as with Mr. Cooper, a surprising amount of the play’s emotional weight finds its way into his seemingly carefree material.

Even when his Teddy is in pure jokester mode – his description of a dimwitted, bagpipe-playing whippet dog formerly in his employ is as funny a set piece as you’ll find in any non-comedy – Mr. McDiarmid shows glimmers of the enormously complex relationship Teddy has with his meal ticket. Reverence, frustration, disappointment, love, envy: All of these flash over Teddy’s face, albeit channeled through a showman’s bluster.

Mr. McDiarmid’s irresistible prattlings give this “Faith Healer” the first and only real sense of breaking free, of elevating the text rather than obeying it. When Frank looks back on his marriage earlier in the play, he says of Grace’s steadfastness: “That very virtue of hers – that mulish, unquestioning, indefatigable loyalty – settled on us like a heavy dust.” A similar dust of piety hangs over this well-intentioned but enervating revival. Even on those increasingly common days when Frank’s powers evade him, he’s never laid his hands on a vibrant body and left it paralyzed. Mr. Kent comes perilously close to doing just that.

Open run (222 W. 45th Street, between Seventh Avenue and Broadway, 212-239-6200).