The Strike team's attempt to play by the book comes to an abrupt end when they discover that two gangs, the Byz Latz and the One-Niners are attempting to alter the balance of power by acquring MP5s. Claudette and Dutch investigate the murders and feet decapitation of 4 Armenian men by the Armenian mob in their search for the stolen cash from the money train. Meanwhile, Danny who is doing temp work at a high school while waiting for an appeal, discovers she might me be able to get her old job back.

When two high profile murders are linked to each other, Aceveda orders Wyms to get the entire Barn involved before gang and racial violence breaks out. Mackey uses the case to leverage himself and the Strike Team back into the streets of Farmington.

Vic is no longer the cop he used to be, acting adrift after his past actions have caught up to him. The strike team has been dissolved, leaving Mackey to menial busts that keep him off the streets. When Aceveda moves on to his new City Council position, Captain Monica Rawling takes over the Barn and empowers Vic to implement her controversial anti-gang policies.

Just as Monica and Vic get close to a big break in the Garage Sting, Chief Phillips unexpectedly hands over the bust to the Organized Crime Unit. He blames the decision on an emerging PR scandal involving a videotape of Vic at the church bust that was leaked to the Assistant Chief through Aceveda's office. Vic uses his leverage with the Byz Lats to find a Russian mob leader before the mobster flees the country. Monica threatens two foster care social workers with jail after a young girl is found close to death in her foster home, then tells Julien if he doesn't put in for a transfer, she'll request one for him herself.

Vic and the Strike Team use their leverage on the One-Niners to track down anyone involved with the cop killings. Their hunt leads them down an unexpected path with the Russian mob. Monica puts pressure on the team to come clean about any of their dealings with Antwon. Dutch and Claudette investigate a gang shooting and soon realize their key witness is close to the Barn, and has something to hide.

Vic and his crew track down the Russian who was involved with the cop murders, but they lose control during his interrogation and the hit man dies in an explosion before they can get any answers. Meanwhile, Aceveda is blackmailed by the man who assaulted him. Plus, Rawling's seizure is on the verge of being shelved.

Monica, Vic and the strike team work together to put Antwon Mitchell back behind bars after his deal with the DEA released him from prison. When Vic reveals his suspicions of David's connection to both Antwon and an inmate's murder, David must protect his political future at any cost. When the murder of an over-protective father leads Claudette and Dutch back to a foster home they had previously investigated, Monica makes an unpopular decision that helps seal her fate.

As racial tension in the area escalates, the Strike Team attempts to end a race war, while Claudette and Dutch investigate a riot at a high school. Meanwhile, an Internal Affairs officer begins his investigation of Vic and the Strike Team by first zeroing in on Lem. A pregnant Danny refuses to reveal the identity of the father, and Julien begins training a rookie cop named Tina Hanlon.

With the Barn grieving over the loss of one of their own, Vic's out to avenge his friend's murder, but finds himself in the crosshairs of Kavanaugh. Claudette assigns the Strike Team to investigate the torching of a methadone clinic. Meanwhile, Julien and Tina look into a robbery/assault at a porno shop, and Dutch makes a horrifying discovery in San Marcos.

After Vic disowns him, Shane turns to the Armenian mob for help. Vic gets more involved with the San Marcos investigation, while Dutch and Billings are able to track down someone who survived the massacre.

As a local gang war heats up, Vic positions himself as a valuable commodity to the warring parties; Corrine and Cassidy confront 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.