Grand Canal Theatre, Dublin

Like so many material witnesses in a murder case, musical theatre doesn’t object to seeking refuge in unlikely places. The unrepresentative poetry of TS Eliot? Why not? A particularly bloody Stephen King novel? So be it. The back catalogue of a Swedish pop band? Mamma mia!

Movies, however, provide a safer haven for a tuner on the run – particularly if – like The Producersor Hairspray– they were already song-heavy to begin with.

With some very modest tweaks, the plot of Sister Actis familiar to anyone who has been blessed with a DVD player and a hangover. It is 1978 in Philadelphia and Deloris Van Cartier (a very fine Cynthia Erivo), a lower-rung showgirl, decides to leave her no-good boyfriend, a gangster and adulterer who, worst of all, may not respect her talent. Before you can say, "You go, girl!", she sees him whack an extra, and, aided by a decent police officer (Edward Baruwa) and mildly resisted by an implacable Mother Superior (Denise Black), she is spirited away to the last place the gangster would ever find her: a 1992 Whoopi Goldberg movie.

So begins the trade off: Sassy Deloris is granted sanctuary and opportunities for self-mortification while she puts some pizzazz into the convent choir, who render their hymns, amusingly, like a bitter gale wheezing through a broken roof. Will the mobsters catch up with her? Will the choir get their groove on? Will Mother Superior ever lighten up? Oh, take a flying guess.

The wicked conceit of Sister Actthe movie was its gospel of soul, remoulding Motown love songs as devoted hymnals ( My God, I Will Follow Him). That made the joke of repressed sexuality more piquant and the joys of rhythm more subversive – was it any wonder that timid Sister Mary Robert seemed more awed by the thrill of her own voice than by her own husband, Jesus? Alan Menken's musical version, on the other hand, is entirely original and almost completely forgettable. When I Find My Babyis an appealingly warped Jackson 5-inspired number, but you'd be hard pressed to recognise a single tune from a police line-up. One exception is Take Me To Heaven, but only then because it is reissued more frequently than a responsorial psalm.

This will not matter a jot to the faithful, a devout Sisterhood who still believe in the tenets of nights out with friends rather than sitting at home, worshipping an X-Box. The show may treat nuns as a chorus line of indistinguishable penguins in search of sequins, as though not entirely convinced that such creatures really exist. But it certainly believes in customers. When the choir has been rejuvenated, even the Monsignor becomes evangelical about higher church attendances and heavier collection plates.

This may be Sister Act's one unshakeable faith: good box office.

Until Jan 7