In early 1950s Los Angeles, Patrolman Sergeant Edmund "Ed" Exley (Guy Pearce), the son of the legendary LAPD detective Preston Exley, is determined to live up to his father's reputation. His intelligence, insistence on following regulations, and cold demeanor contribute to his isolation from other officers. He exacerbates this resentment by volunteering to testify in the Bloody Christmas case in exchange for a promotion to Detective Lieutenant. This goes against the advice of Captain Dudley Smith (James Cromwell), who states that a detective should be willing to shoot a guilty man in the back for the greater good. Exley's ambition is fueled by the murder of his father, killed by an unknown assailant, whom Exley nicknames "Rollo Tomasi".