"Diabolique" is a 1955 French psychological thriller directed by Henri-Georges Clouzot. The film follows the story of Christina, the wife of a cruel headmaster, and her lover, Nicole, who conspire to murder him. After the deed is done, they face unexpected consequences that lead to a tense and suspenseful unraveling of their plan. The film is renowned for its innovative storytelling and shocking twists, influencing the thriller genre significantly. It is based on the novel "Celle qui n'était plus" by Pierre Boileau and Thomas Narcejac. "Diabolique" remains a classic, celebrated for its atmosphere and psychological depth.