Harlee (Jennifer Lopez) and her rookie partner, Loman, go out on a call to check out an apartment where they may be selling heroin. While Harlee gets a small girl to go back into her apartment, Loman hears a shot, kicks in the door and shoots and kills a man who was sitting on the sofa. Turns out the man was only playing a video game but there is a duffel bag full of heroin, a gun, and a guy with yellow sneakers who bolts out the window.
Harlee covers for Lohman. She takes the gun from the duffel bag and shoots the door, then she shoots Loman in the vest much to his shock and spins a story that the dead man had fired first. Loman is shaky on the story and wants to tell the truth but Harlee tells him that the badge he carries makes them family. She saved his ass, now it’s his turn to save hers. He sticks to the story.
Harlee’s boss, Lt. Matt Wozniak runs a tight knit team, including Harlee, that keeps drugs away from schools and parks by making deals with the local drug lord, Raoul Mendez, and taking cash from dealers and bookies which they all divvy up. Woz and team are family to Harlee and her teenage daughter Cristina who is a cellist at a high-end private school but Harlee can’t make the bills. Woz says he’ll get it for her and he might have a big job coming up that can help them both.
The team tracks down the drug dealer with the yellow sneakers, Earl, who ran from the shooting. Turns out Earl and the dead man were running drugs in Raoul’s territory without his okay. When Earl threatens to tell the truth about the shooting, Woz turns him over to Raoul who want to make an example out of him for selling in his territory without permission.
Woz sends Harlee to talk to a new bookie who is looking to get in on the action. Just as she makes the deal with him and he hands her a bag full of cash, the FBI pulls up. The bookie was an undercover agent. Special Agent Stahl, part of the anti-corruption task force, tells Harlee she has two choices. She can either be arrested and lose everything, including her daughter, or she can be an informant for the FBI.
When Harlee gets a call from Woz and has to cover as she’s in FBI custody, she tells him she can’t come to him because her daughter’s friend smashed Cristina’s car. Later, Harlee gets to watch her daughter play a solo at a school concert and tells the FBI she’s in just as Woz hands her $10,000 to pay for her daughter’s school.
The FBI breaks into Harlee’s apartment and takes her favorite necklace given to her from her daughter. They install a camera and a listening device. Harlee isn’t happy but she wears it to a bbq with the team.
Woz gets a phone call at the bbq and pulls Harlee aside. He’s obviously furious. He says he just found out that there’s a rat on his time, an FBI informant. Harlee is doesn’t move as he rants and the FBI listens in. Then Woz says he needs to kill the rat…and he needs Harlee to help him.