Double Indemnity Author is James M. CAIN, a four-letter word. James M. CAIN was an American author and journalist whose works are considered part of the hardboiled school of crime fiction. He wrote several novels, including The Postman Always Rings Twice, Mildred Pierce, and Double Indemnity. His works were adapted into films, and he was posthumously inducted into the Mystery Writers of America Hall of Fame in 1998.