In the mid-1970s, the newly formed DEA recruits two Mexican-American street cops: Kiki Camarena and Hector Berrellez. Kiki is assigned to Guadalajara, home turf of the Guadalajara Cartel, while Hector targets cartel operations in Los Angeles. The Cartel is putting cops on its payroll, including three Jalisco state policemen. When Kiki is kidnapped it rocks both sides of the border.

After Kiki's murder, Hector gets reassigned to Mexico where he ends up leading DEA agents and Mexican soldiers into the longest and deadliest shootout in DEA history. While this puts a million dollar bounty on his head, it also impresses the DEA brass, who then decide to put Hector, one of their most aggressive narcs, in charge of the investigation into Kiki's murder.

Hector identifies the mysterious Cuban who interrogated Kiki as veteran CIA operative Felix Rodriguez, a key figure in the Iran-Contra scandal. Although warned not to take his investigation further, Hector refuses and is eventually forced into retirement. The case languishes for years, and then a new source comes forward with a shocking allegation.