Perri O’Shaughnessy is the pen-name for two people, Pamela and Mary O’Shaughnessy, sisters. The authors' pseudonym is an homage to Perry Mason, the man who never met a guilty client, and a melding of their two first names, Pamela and Mary. O’Shaughnessy is their paternal family name. They are the authors of eleven bestselling Nina Reilly novels as well as a collection of short crime fiction, Sinister Shorts.