Deloris Van Cartier (born Doris Carter), a sassy, brassy, none-too-successful nightclub singer, witnesses a gang murder, runs for her life and makes it to the police station. Needing a safe place to stow her until she can testify, the cops hide Deloris in a convent, disguised as a nun.

There, she is put in charge of the convent’s dismal choir with results that could justify “Sister Act” being called “The Miracle Worker” if that title weren’t already taken.

Based on the popular 1992 movie, the musical “Sister Act,” directed by Broadway luminary Jerry Zaks, strives mightily to please audiences and mostly succeeds. The cast is a high-energy delight. Ta’Rea Campbell’s Deloris (Whoopi Goldberg’s role in the movie) carries a truckload of attitude and a powerhouse voice. Hollis Resnik, in the Maggie Smith role of Mother Superior, has a gravitas all her own. If Deloris is brass, Mother Superior is steel and their clash resonates throughout the show.

Mother Superior’s intense dislike of Deloris seems disturbingly unholy, going well beyond the differences between an old-school nun and a would-be diva. The tension between Deloris and Mother Superior provides the musical with a third major story, the other two being the gangsters’ pursuit of Deloris and Deloris’ wondrous effect on the choir.

Still, all the main plots and subplots of “Sister Act” aren’t substantial enough to justify as many songs as there are (including four reprises), and you feel the show sagging under the weight. The show is set in Philadelphia in the late ’70s and the songs, all new, by Alan Menken and Glenn Slater, frequently harken back to the era of disco and Philly soul.

On the plus side, everyone sings well and the show’s secret weapon is its choreography by Anthony Van Last. The secret is there aren’t any dance numbers per se, but there is a plethora of chorus movement and small-group choreography that conjures the late Cholly Atkins, Motown’s house choreographer.

And underlying everything is a sweet and potent message about transformation. Except for the mob boss (played with malevolent consistency by Melvin Abston), everyone changes for better. Deloris learns to think about something other than herself; Mother Superior warms up; a timid nun (played sweetly by Ashley Moniz) discovers her backbone; and the cop (Chester Gregory) who has had a crush on Deloris since high school gains the confidence to declare it.

Maybe the show should be called “The Miracle Worker” after all.