You can't quantify belief. It seems to exist to defy. The questions raised by Neil D'Souza's new play A Small Miracle flutter around this premise much as the music and dance steps of Janice Dunn's production weave between Irish and Indian modes.

Two characters stand out, and they are only superficially exact opposites. There's the widow, who followed her husband in an arranged marriage from Bombay to Birmingham and whose eclectic Hinduism finds room for the Virgin Mary as well as Sitala. And there's the troubled Irish teenager with a backpack of personal tragedies dragging her down the spiral staircase to insanity.

Souad Faress plays Meera, a grandmother most youngsters would appreciate - but also gifted with the capacity to be the proverbial mother-in-law from hell. Ella Vale is Sadie, elfin in more senses than one. They play out their personal dramas in a caravan park, near the Marian shrine of Knock, in County Mayo.

They're at the caravan park because Sadie's Irish mother Bronagh (Gina Isaac) and her new partner Arjun (Kulvinder Ghir), who is Meera's son and wants to exchange his well-paid but boring desk job for the exciting uncertainties of a literary career, are on uncomfortable holiday. Bronagh needs security after one failed marriage. Arjun wants to do what is right.

But what is right? And is one person's right, or need, paramount when there are other people caught up in the situation? And what of the future?

Caravan park manager Barry (Peter Dineen) has some of the answers, but also even more questions. Because Chloe Lamford's staging confines the action by having the audience sitting on three sides of what is basically a theatre built on the stage itself, we are at the same time spectators and participants. This can be an uncomfortable situation. It's impossible to drop the audience's usual fourth wall as an armour against prejudice and persuasion.

"A marvel - like a miracle, only smaller" is how one of the slightly inexplicable, rationally implausible off-stage happenings is described. Belief systems don't come into the equation. Or do they? After all, what else is theatre?

- Anne Morley-Priestman (reviewed at the Mercury Theatre, Colchester)