They’re in a choir and they sing the sign

A Reno singer witnesses a mob murder and the cops stash her in a nunnery to protect her from the mob's hitmen. The mother superior does not trust her, and takes steps to limit her influence on the other nuns. Eventually the singer rescues the failing choir and begins helping with community projects, which gets her an interview on TV—and identification by the mob.

Deloris Van Cartier is again asked to don the nun's habit to help a run-down Catholic school, presided over by Mother Superior. And if trying to reach out to a class full of uninterested students wasn't bad enough, the sisters discover that the school is due to be closed by the unscrupulous chief of a local authority.