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.

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.

An oversight puts Waylon and Trish in serious danger during an undercover job and Claudette is to blame. Meanwhile, Tommy makes a drastic decision when he realizes nobody in the Barn can help him get back on the job.

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.

Aceveda finds himself in a near fatal confrontation, and enlists Vic to help him take down the suspects in order to help service his own personal agenda. Meanwhile after losing her position of power, Claudette rejoins Dutch on the search for the cuddler rapist as they get a stunning break in the case.

When a mole in the treasury department is discovered and the framed suspect in the Armenian money train robbery turns up missing, the Strike team race to find the suspect before their cover is blown. Meanwhile, Claudette attempts to make amends with the Decoy Squad by going undercover to help them on a case.

When Aceveda confirms that the Strike Team is the target of an Armenian mob hit, Mackey must take matters into his own hands. Meanwhile, Whym's career is on the line when she disobeys Aceveda's orders to put a case to rest that may prove the innocence of convicted felons.

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.

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.