In 2015, Los Angeles Times investigative reporter Darius "Jack" Jackson, Forest Whitaker, is assigned to cover the murder of the Notorious B.I.G. (Christopher Wallace), and he meets the retired and disgraced LAPD detective Russell Poole, Johnny Depp. Through a series of flashbacks, Poole reveals his theory that Death Row Records CEO Suge Knight paid corrupt LAPD officers to murder Wallace and cover it up.
In 1997, just weeks after the Wallace case, Poole is tasked with investigating the shooting of off-duty black officer Kevin Gaines by a white detective Frank Lyga, Shea Whigham. Poole faces mounting pressure from upper management as Los Angeles wrestles with a wave of race-related tensions, including the Rodney King beating and the O.J. Simpson trial. During the investigation, Poole learns Gaines was on Knight's payroll and had Bloods affiliations. Poole's superior, Lieutenant O'Shea, refuses to credit the theory and orders Poole to close the Gaines–Lyga shooting. Lyga is exonerated but faces a civil suit, with attorney Johnnie Cochran representing the Gaines family. Poole corroborates the link between Knight and Gaines via an undercover FBI source and is reassigned to the Robbery-Homicide Division to pursue Wallace's murder.
Poole and his partner Fred Miller obtain the names of suspects: David Mack, Shamier Anderson; Wardell "Dreadlocks" Fouse, Rockmond Dunbar; and Nation of Islam member Amir Muhammad. Poole learns Mack worked security for Wallace and has ties to a bank robbery. Mack is arrested but does not reveal information about Wallace's death. Poole then tracks Rafael Pérez, Neil Brown Jr, after learning Pérez has been stealing cocaine from the evidence room; Poole intervenes and shoots Pérez in self-defense. Pérez is charged and implicates himself and others in various misdeeds. Poole is granted his own task force and plans to testify in Lyga's civil case, asserting that Mack was involved in Wallace's death and that the LAPD is covering it up, but the city settles before the trial. Lyga fails to clear his name, and Poole is shunned by his colleagues.
Voletta Wallace, Voletta Wallace, files a wrongful death claim grounded in Poole's findings. Mack and Amir Muhammad are named as defendants but are dropped shortly before trial after the LAPD and FBI dismiss them as suspects. Poole resigns in disgrace one month before he would have been eligible for his pension, a move that costs him his family.
Jackson reconnects with Poole and Voletta, and they forge a cautious friendship. Jackson apologizes for a prior article that implied Wallace’s involvement in Tupac Shakur's murder; Voletta accepts the apology, acknowledging Poole's sacrifice. Poole reveals to Jackson that Wallace's earning potential could have reached around $1 billion, and a civil suit could bankrupt the city. One day, Poole visits the L.A. Sheriff's Department in an attempt to reopen his investigation, but he suffers a heart attack and dies some time later.
Driven by guilt, Jackson pens a tribute that casts Russell Poole as a forgotten hero. The piece earns praise, yet Jackson ultimately resigns, feeling the system remains hypocritical and unworthy of celebrated heroes. In the end, the murders of Wallace and Tupac Shakur stay unresolved, leaving a lasting unease about a city grappling with a painful chapter in its history.
