In Carol Denise Mitchell's new book: The Mad Sister -Mercy Jean Diamond was born to African-American heart surgeon Fred Diamond and his wife, Maggie, a reformed prostitute, on July 12, 1928. Ten years later to the day, Mercy's sister Roxy Ann is born, and Mercy loves her baby sister. She reads to her and plays with her and continues to adore Roxy even though Fred and Maggie are terrible to her while they show preference to Roxy. Then, a fire destroys the Diamonds' home and Roxy dies in the blaze. Mercy is grief-stricken but the people of Parish, California, her hometown, watch over her and love her even though Fred and Maggie ignore Mercy and don't even attend her high school graduation. Mercy is a genius, goes to Yale on a full scholarship and becomes a doctor. But Roxy's death has driven Mercy over the edge and she becomes crazy, returning home to rebuild the family home and to sell illegal drugs, earning herself a fortune and scares the townspeople who love her by promising to do scientific, medical research to bring back Roxy. But can Mercy really bring back her long-dead sister?