The story of an inner-city Los Angeles police precinct where some of the cops aren't above breaking the rules or working against their associates to both keep the streets safe and their self-interests intact.
Vic challenges Shane and deals with threats to his family; a federal agent arrives in Farmington to investigate a recent wave of violence.
As a local gang war heats up, Vic positions himself as a valuable commodity to the warring parties; Corrine and Cassidy confront Vic.
Vic works an angle to make himself valuable to the Armenian mob; Corrine finds herself in a surprising legal jam; Tina targets a producer of adult entertainment.
The gang war erupts in unexpected ways that Vic cannot control; Dutch and Billings' homicide investigation grows into something more disturbing; Cassidy reaches out to Danny.
Claudette encounters a murderous old nemesis; Vic confronts Olivia about her political connections; Dutch's case gets personal.
Vic sets into motion plans to end the gang threat as his relationship with Cassidy deteriorates; Dutch and Billings investigate a possible sleepwalking murderer.
A prostitute from Vic's past is the key to taking down a violent drug dealer; Dutch worries about Claudette's health; Danny takes drastic measures to protect her child.
A local priest may be protecting drug dealers; Dutch and Billings close in on attempted cop killers; Corrine learns uncomfortable truths about Vic.
Vic closes in on Shane, Mara and their sick young son; Claudette dismantles the Strike Team; Pezuela offers Acevada "assistance" for his mayoral campaign; Rita Denton (Frances Fisher) comes on to Dutch; and Billings' ex-wife and daughter are fearful when a registered sex offender moves into their neighborhood.
While Shane remains holed up in L.A. with Mara and Jackson, Corinne decides to cooperate with Dutch and Claudette, who's now spearheading the LAPD effort to bring down Vic. Meanwhile, Vic plays Aceveda, Pezuela, Beltran and ICE against each other. But Ronnie's tempted to simply give up and run to Mexico. "And you should run too man" he tells Vic.
Corrine agrees to be Vic and Shane's go-between and also agrees to cooperate with Claudette and Dutch as she does so. Meanwhile, Vic comes to an understanding with Aceveda and seeks one out with Olivia; and Claudette assigns Ronnie to work with Julian to investigate the murder of a high-school football star, keeping Ronnie out of the barn and unable to intercept the letter Shane sent to Claudette detailing the Strike Team's "sins."
Olivia joins forces with the Strike Team to catch a Mexican drug king and his shipment. Meanwhile, Dutch cleans up Billings' mess, and the death of a woman associated with the Strike Team prompts an investigation by Claudette.
Officers in the Barn investigate a woman's disappearance and the arrival of a large drug shipment; lives change forever.