After completing Katherine Gibbs Secretarial School, Andrea Davies takes a position at a large New York Advertising Firm, admittedly there to find a husband and secure a life as a well-to-do, country club socialite. Andrea meets Richard Hayes, one of the firm's partners and an inexplicable attraction takes hold. To everyone at the firm, Richard is the powerful yet kind and respectful executive with tragic home life. He is the devoted husband to Margaret, a dangerous "lunatic" who is in and out of psychiatric hospitals. The attraction between Richard and Andrea intensifies when she is promoted to his secretary. When Andrea turns her attention to another marriage prospect, Richard quickly reveals a sinister, unpredictable side that naive Andrea interprets as unbridled passion, fueling her romantic delusion of "love at any cost." Andrea becomes increasingly drawn into Richard's bizarre personal life. She begins to assume the role of his wife and mother of his children. However, a parallel reality continues back at his apartment where his psychotic wife moves in and out of insanity. A neo-noir thriller, The Diarist, explores the darker side of the human psyche and the terrifying consequences of indulging in base desires.