Sister Mary Helen, aged seventy-five, had resisted retirement. She feared she'd find only prayer, peace and a little pinochle. But she had no sooner arrived at Mount St Francis College for Women when she was greeted by an earthquake, a hysterical secretary and a fatally bludgeoned history professor. Police inspectors Kate Murphy and Dennis Gallagher promptly make a very human error when they arrest an innocent. Perhaps by divine inspiration, Sister Mary Helen knows a mistake has been made and turns her own talents into a hunt for the guilty. Nothing is sacred when it comes to catching a killer with a habit for murder.