Mackey tries to help an old acquaintance find a wayward teenager, but the search quickly turns ugly when the missing teen appears to have been involved in a shoot-out. Meanwhile, Shane heads out into the field with his new partner Army, teaching him shady police tactics and seeing how far he'll go to be partnered up. Plus, Aceveda spends his last day trying to bury Vic for good, which makes things difficult for Rawling trying to take his place.

With Farmington on the brink of a gang war, Monica and Vic race to find the catalyst and stop the bloodshed, enlisting Antwon's help along the way. Still in the doghouse, Dutch decides to take action in thawing the relationship between Claudette and the D.A. Danny and Julien get up close and personal with the Farmington 1-Niners, while Monica looks to Vic for support when the implementation of her property seizure policy challenges her morality.

In a routine sweep, the Barn's detectives divvy up warrants. But when they cast their nets, they bring up far bigger fish than expected. While Vic holds a basketball star hostage to influence the outcome of an upcoming game, Dutch and Claudette nab an egotistical rapist out to impregnate as many women as possible.

Flashback to the first day of the Barn. Under pressure to get results, Vic and the newly-formed Strike Team make an impression on the streets. Dutch and Claudette realize they make a good team, and Aceveda discovers he doesn't have as much power as he thought he would.

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.

When Monica puts Vic on the trail of an escaped fugitive in Farmington, he must continue to prove his worth while playing it straight. Claudette gets suspicious of the D.A's motives when she and Dutch are assigned to investigate a major drug dealer who ends up being a minor offender. David seeks an illicit outlet for the troubling feelings caused by his rape. Vic decides to bring Shane closer as his fears about Shane's connection to Antwon Mitchell rise.

Vic attempts to broker a peace agreement between two rival rappers after a dispute over an up-and-coming singer's success erupts in a gang war. Danny is attacked after identifying a shooter, Julien helps a woman whose son's body has been stolen, and Dutch and Claudette search for a missing migrant worker.

A planted gun in a truck-jacking case causes complications for the Strike Team, and Lem attempts to set things right. Meanwhile, the rift between Danny and Julien deepens, causing Aceveda to intervene, and Claudette deals with the mess of her family during a visit from her father and daughter.

When the ex-wife and child of Julien's former partner, Tommy, are murdered, Tommy becomes a suspect, prompting Julien to team up with Mackey to conduct their own investigation. Elsewhere, Shane goes undercover to catch a group attacking gay prostitutes, and Claudette and Dutch investigate a rape case against Aceveda's orders.

Vic and Monica stake a deal with the DEA to shut down Mitchell's tar heroin operation. When the bust comes up empty, Vic's suspicions of Shane grow, until Shane proves himself by coming up with a key piece of evidence that reveals a large stash of tar being stored at a local church. Meanwhile, Dutch and Claudette's friendship continues to feel strain as they try to tie a young woman's murder to a suspected serial killer. Plus, Julien takes a stand against Monica's policy, then goes to David for support when she suggests he consider transferring out of Farmington.

Following the murder of Terry, the Internal Affairs Division begins an investigation into his death, while Aceveda begins his own. Meanwhile, Dutch and Claudette investigate the shooting of a churro vendor that ends in the Barn's detectives busting up a gang initiation.

Vic decides to use some of the money train robbery cash during a gun-running sting operation, but after it goes awry, tension within the Strike Team begins to mount as its members attempt to rectify Vic's mistake. Meanwhile, Dutch and Claudette seek the help of a college student named Esteban who was the only survivor in the murder of two Latino gang members.

The newly arrived Decoy Squad and the Strike Team go head to head in the investigation to solve a car-jacking case. Dutch gets in over his head on an attempted murder case.

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.

The Strike Team tries to develop a strategy to deflect the Internal Affairs investigation as Vic finally comes face to face with Kavanaugh. Meanwhile, Tina goes undercover to help take down a sex-trafficking ring; and friction between Claudette and Dutch deepens when she reopens one of their past cases.

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

Vic's relationship with Shane becomes even more complicated when the pair team up with a detective from another precinct to investigate the murder of several gang member. Meanwhile, Dutch and Claudette bring in a psychic on a complaint from the son of one of her clients.

Vic and the Strike Team mediate a dispute between Rondell Robinson and the Nation of Islam, while Dutch and Claudette investigate a brutal home invasion in the district's Korean community.

Now that Vic is back to work, he and Shane go undercover as dirty cops to find the man behind a robbery and murder. Dutch and Claudette track down an old rival of Claudette's after a turned-in gun is found connected to an unsolved case, while Aceveda assigns Julien and Danny to watch over a Korean parish in an attempt to secure the Asian vote in the election.

Monica orders her units to turn the streets of Farmington inside-out when two officers mysteriously disappear after answering a 911 call. Shane tries to make amends with his old crew after Vic agrees to help him get out from under Antwon, but things don't work out as planned. Dutch and Claudette convince Monica to let them take active roles in the case of the missing officers, but soon find themselves at a dead end with the only witness being clinically insane.

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.

Claudette encounters a murderous old nemesis; Vic confronts Olivia about her political connections; Dutch's case gets personal.

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.

Allegations against the Strike Team are front-page news, and the team is reassigned pending the investigation. Vic and Claudette find themselves following the trail of a deadly meth batch, while Shane and Dutch team up to investigate the unsolved murder of a widow's husband.