Kern County Patrolman Joe Deacon, nicknamed Dick (Denzel Washington), is sent to Los Angeles on what should have been a straightforward evidence-gathering mission. Instead, he is drawn into the hunt for a serial killer ravaging the city. Leading the hunt is Los Angeles County Sheriff Jim Beckster (Rami Malek), who is so impressed by Dick's police instincts that he seeks his assistance privately. But as the two track down the main suspect, Albert Sparma (Jared Leto), Beckster is unaware that the investigation brings back unpleasant memories of Dick's past, and the dark secrets unearthed may have more implications than just threatening the investigation.