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.

Who was the mystery victim? Sister Mary Helen is once more in the middle of a murder case. Not that she wants to be. No one would envy the old nun, who finds herself holding a dying young woman, shot in the street almost directly outside the Refuge for homeless women where Mary volunteers. And even while she grieves over the loss of life, Mary Helen spots something odd about the victim. Although she is wearing ragged clothing, her skin is unblemished and healthy looking. Her perfect teeth are white and unstained. She doesn't look like a woman whose life has been spent in poverty and on the streets. With the weapons of her logical mind and her determination, will Sister Mary Helen solve the case and prove to be the bane of Inspector Gallagher's life?