“Astonish me!” Sergei Diaghilev famously demanded of the poet Jean Cocteau; this past week and the next at the Vineyard Playhouse — until Sept. 16 — the theatre does exactly that. From the moment the audience arrives and is ushered not to the theatre but to tables and chairs downstairs in a pub setting or, as the trio of actors all iterate, “a lounge bar, really,” the astonishment begins.

All but one of the lights dim as Irishman Frank Hardy (Patrick O’Brien) unburdens himself of his triumphs and tragedies. In Faith Healer, the 1979 work by playwright Brian Friel, who would later give us Dancing at Lughnasa, Frank has the charisma of a charlatan or a holy man. In reality he’s both.

The gift appears unbidden; more often it eludes him. The sheer wonder spiked by crushing unpredictability has driven him to the edge of madness. In shabby churches and crummy meeting halls in small towns of Wales, Scotland and Ireland, Frank chases his obsession to cure, but the legion of uncured haunts him. He drowns his disappointment with whisky.

About his ability to sometimes perform miracles he cries, “I did it because I could do it. Occasionally it did work.” He also possesses a startling prescience of failure: “I always knew, drunk or sober, that nothing was going to happen.” Thus he’s constantly balanced “between the absurd and the momentous.”

In his sotted and insane lurches from venue to venue, he drags his wife – he calls her his mistress — the despairing and devoted Grace (Sandra Shipley) with him. Also caught up in years of bleak, nomadic healing sessions is Frank’s manager and tout, the irrepressible cockney Teddy (Gerry Maher). Constantly broke and often living in the back of their van, Grace and Teddy are kept in thrall by Frank’s volcanic personality and his occasional, but impossible-to-control, portal to the sacred.

All three characters regale the audience with contradictory tales of their dramatic and derelict times together, making of each other pathological liars. Was there a baby buried in a field in Scotland? Was Teddy in love with Grace? Did Frank cure him of this impossible malady?

Three social classes mingle and clash in this trio. Frank is of a solid working class background from County Donegal, a land he has managed to avoid for over 20 years. Teddy was reared in the mean streets of London, yet his innate kindness rises above the self-absorbed frenzies of patrician Grace and yeoman Frank and their messy passions.

In serial monologues, the three players pull the audience along an excruciating timeline culminating in a pub, a lounge-bar really, back in County Donegal. A riveting, horrible showdown is at hand, and we fear it will end badly. Yet we know it for what it is: Frank’s appointment in Samarra. And if it comes to pass, we also know that Teddy and Grace will be obliterated in Frank’s last self-annihilating blaze of glory.

Mr. O’Brien is superb as the mad healer. Ms. Shipley supplies the heart and wrenching pathos of the tale, and Mr. Maher reels in the reality base as a talisman against Frank and Grace’s ghastly folie à deux. Joann Green Breuer, founder of the Cambridge Ensemble and teacher of acting at Harvard, directed and designed this fascinating and unusual presentation.

At intermission, some members of the audience seated at central tables expressed a level of discomfort at following the roving players. Nonetheless, one is left with much to digest, and it’s impossible to rise from one’s seat in this pub, a lounge bar really, without feeling, to a degree, transformed.

Costume design is by Chelsea McCarthy, sound design by Jim Novack, lighting by Fred Hancock; stage manager is Kate Hancock. The ever-splendid artistic director M.J. Bruder Munafo is on deck. Christopher Kann is master carpenter, house managers are Robert B. Porter and Linda Smith, box office, Geneva Monks and graphics and publications, Stephen M. Zablotny.