Frannie (Meg Ryan) is a lonely New York City high school English teacher, who is compiling a dictionary of urban slang with the help of one of her students. Frannie "discovers the darker side of passion" after becoming involved with a tough homicide detective investigating a series of murders in her neighborhood. As the plot develops, she begins to wonder if the detective (Mark Ruffalo) might be the murderer, but remains curious and passionately interested in him. When Frannie's younger half-sister (Jennifer Jason Leigh) is decapitated by the murderer, her doubts about the detective increase, despite her inability to distance herself from him. Finally convinced of his guilt, Frannie runs away from the detective, only to fall deeper into the web of the murderer.