When the body of a young hooker is found in the district, Dutch's theory about a serial killer preying on prostitutes proves true. Aceveda launches an all-out effort to find the killer before he strikes again, giving Dutch and Claudette the full resources of the Barn for 24 hours and the help of the FBI.

As Dutch uncovers a lead to the serial killer, a reporter's questions force Aceveda to explain problems he thought were buried fair in the past, while Vic assists Connie as she tries to quit crack cold-turkey in a desperate attempt to keep her son, leaving the other Strike Team members to investigate a strip-club mugging ring on their own.

Aceveda turns to Claudette after a double homicide raises ire and fear within an ignored community. Vic is forced to help Gilroy avoid being implicated in a hit-and-run, while Shane and Lem follow the trail of a gunrunner with a penchant for cockfights.

Still fuming from the murder of Tio and his brawl with Armadillo, Vic takes a day off to reconnect with his old partner, and soon sets out to help him get revenge against the thug whose complaint forced him into retirement. Meanwhile, an amputated arm sends Dutch and Claudette in search of the sadomasochistic criminal behind the torture and mutilation of a woman who may still be alive, and tensions brew between Danny and Julien after Julien fails to back up Danny's side of the shooting to IAD.

Vic and the Strike Team begin to prepare for the money train takedown, even though Armadillo's greenlight still has them on their toes. After embarrassing the department with the Bob and Marcy case, Dutch is forced to take any action necessary to prove himself in a new homicide, while Vic sets out to stop the abuse of a neighbor by her violent boyfriend, and Danny finally makes a stand against Yassirah.

A prostitute and friend to the late Connie named Farrah seeks the help of Vic in an effort to bring down her pimp. After failing to convince Vic to help her, Farrah goes to Claudette, who assigns Vic to the case against his wishes. Meanwhile, Dutch investigates the rape of an elderly woman.

When Aceveda assigns The Strike Team to serve a high risk warrant against a mob killer to service his political agenda, they find themselves embroiled in a hostile struggle with the Korean community. Now the Team must find out how to put an end to the situation before they end up casualties of a racial fued. Meanwhile, one of Vic's informants works with Danny on finding stolen chairs, while having eyes for her.

With an Armenian hit-man hot on their trail, the Strike team sweeps the streets of the Armenian community to find him before he finds them. After catching a break, Aceveda's suspicions grow about the Strike Team's involvement with the Money Train robbery. Meanwhile, Dutch and Claudette investigate a case that could repeal hundreds of convictions, which leaves Claudette having to choose between her conscience and her career.

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.

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 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.

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.

Kavanaugh seeks the help of Antwon Mitchell in his ongoing quest to take down the Strike Team. In the midst of this, Kavanaugh has a lot on his mind as his ex-wife reenters the picture, and he reluctantly agrees to let Vic send Emolia undercover to infiltrate a Salvadoran gang that is stockpiling grenades.

Kavanaugh acquires what he needs in order to apprehend Vic who is preoccupied with getting revenge on Guardo. Claudette finds herself under the political microscope as a result of the San Marcos incident, and Danny receives some news about her future at the Barn.

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.

Claudette notices Hiatt's mistake when he makes an arrest, and Billings delivers shocking news to the department. Vic forms an alliance with Aceveda, while he waits for his review board hearing. Meanwhile, Shane's life keeps spiraling out of control.