Police officer Vic Mackey and the Los Angeles Police Department attempt to rid the city of crime, using their own unconventional, and often illegal, methods.
Vic and Shane's relationship continues to deteriorate as they work to track down the Armenian hitman, and the war between the Mexicans and the Salvadorans continues.
Vic plans to play the Armenians against the Mexicans, Dutch plays hardball to get a witness to a murder to step forward, and a new mayoral initiative backfires.
Gardocki gets fed up with Vic as he sets up a plan behind Shane's back to get the Armenians on their side, and Dutch tries to get Danny a desk job to protect her.
Vic tries to convince Cruz Pezuela that the Armenians stole the 'blackmail box' that Aceveda took from him, but his ruse has more unintended consequences.
Vic learns that a federal agent is in the 'blackmail box' and has ties to Cruz Pezuela, and Dutch tries to find out if he has a future serial killer on his hands.
Vic launches his latest plan to get rid of the Armenian threat as a ghost from Shane's past re-emerges.
When Vic loses his hearing and faces early retirement, he also loses favour with Cruz Pezuela and begins playing hardball with Danny about the rights to their child.
Shane's plan to get rid of Vic and Ronnie falls apart as Cruz Pezuela asks Vic to strong-arm a priest.
Vic turns in his badge a week early and sets out to find and kill Shane and his wife, but Ronnie is benched after Claudette shuts down the Strike Team.
Vic puts a price on Shane's head and is asked to prove his loyalty to Beltran by killing Pezuela.
Everything falls into place for the sting operation to bring Vic down, Shane is desperate for money, and Ronnie tries to intercept a blackmail package at the Barn.
Mara breaks her collarbone and accidentally shoots and kills an innocent person, and Vic contemplates hanging Ronnie out to dry and taking a deal with the Feds.
Vic hopes that his immunity deal will help keep his family together as Shane takes extreme measures to keep his pregnant wife from being charged with murder.