Sandra Bullock stars as homicide detective Cassie Mayweather, a crime scene specialist on the trail of two high school students, Richard Haywood (Ryan Gosling) and Justin Pendleton (Michael Pitt), who may have committed the perfect crime. The students believe that with Richard's cunning nature and Justin's intellect they have created the "perfect" criminal mind and can elude the law at will. Known in the department former ability to solve cases with her gut instincts and take-no-prisoners style, Cassie is saddled with an inexperienced new partner, Sam Kennedy (Ben Chaplin), who plays it strictly by the book. The homicide detectives must find a way to work together as they uncover a trail of shrewdly concealed evidence that links a murder to the boys.