In this seventh outing for Sister Mary Helen and her co-conspirator, Sister Eileen, the two nuns take time out from their duties at Mount St. Francis College in San Francisco when a wealthy widow, a benefactor of the college and dear friend, is the third victim of a local rapist-murderer. And if that weren't enough to make the nuns take the crime personally (and infuriate the homicide detective in charge, who has had experience with these feisty religious elderly before), the policeman husband of a former student (herself a cop) is severely wounded in a confrontation with the criminal. Between juggling their regular duties, ducking the notice of the detectives on the case, and attempting to straighten out the life of a sad young woman employed by the college library, Sister Mary Helen and Sister Eileen have their hands full. But as criminals, law enforcement types, and their fellow nuns have discovered, there's no stopping the pair if they feel their involvement is called for.