Innocent But Guilty is a Mary Ellen Hatcher mystery. Mary Ellen, with the aide of her older sister, Sister Mary Margaret McMurray, must prove the innocence of her twin sister, Mary Elizabeth Macy. The story begins when Elizabeth calls Ellen informing her she has signed her divorce papers and is on her way. A few hours later, Elizabeth's soon-to-be ex-husband is found murdered and Elizabeth is not a soon-to-be divorcee but a wanted widow! In her pursuit to prove Elizabeth innocent, Ellen travels from Newcastle to Pendleton to Albuquerque and is mistakenly identified as Elizabeth, which nearly gets her killed; aided by FBI Agent Carol Hernandez and her friend, Newcastle police officer Bernard Lawrence prove Elizabeth's innocence.