Harlee Santos, a detective from a tight-knit group of Brooklyn cops with questionable tactics, is arrested by an FBI agent who wants her to work as an informant.
As Harlee grapples with becoming an FBI informant, Wozniak is suspicious of his crew members; a dark secret is revealed; Espada tries to help Tess.
Harlee refuses to relinquish evidence that incriminates Wozniak, but instead hands over an unofficial case involving a murder by a 3-D printed gun; Wozniack decides to confront Harlee.
Loman's loyalty is tested as he struggles with guilt. Wozniak finds out that Donnie is withholding information.
A local drug lord finds out Wozniak's secret and attempts to use it against him to recover drugs that Harlee and Tess confiscated. Harlee wonders about Stahl's motives and decides to spy on him.
Harlee has to try and persuade Stahl to arrest Saperstein in an effort to keep him safe from a suspicious Wozniak, Harlee's abusive former partner claims somebody else is responsible for the crime he is imprisoned for.
Wozniak finds it hard to deal with guilt as he attempts to deal with an unfinished task. Harlee needs to protect Saperstein whilst holding the unit together.
Something happens that makes Harlee decide to help with Stahl's investigation. A couple of abusive policemen harass Harlee's daughter and her boyfriend.
Some details concerning Wozniak's secret relationship are revealed. Wozniak takes charge of a huge job.
Harlee and Wozniak talk to Donnie's silent partner, who ends up being a DEA agent. A Marine veteran is suspected of committing murder.
As the heist is about to happen, Harlee realizes Stahl can not be trusted. Miguel finds out Harlee's secret.
Harlee and Wozniak attempt to deal with the consequences of the heist's money disappearance. Harlee informs the FBI that she will get the money back.
Having not being able to provide the FBI with Donnie and Linklater, Harlee comes up with a deal to Stahl to try and save the team.