Harlee Santos takes drastic measures to cover up the murder of her abusive ex, Miguel. Lieutenant Matt Wozniak makes a deal with FBI Agent Robert Stahl to keep himself and his crew out of jail but soon discovers Stahl has led him into an impossible trap. As the crew deals with the fall-out from the failed heist, Tess struggles to keep her painful gunshot wound under wraps.

Following Wozniak's discovery that Stahl's target is his close friend and Mayoral Candidate, Julia Ayers, Wozniak launches an all-out war with Stahl. Meanwhile, Harlee dives into an investigation that takes an unexpected turn into her own past.

After Wozniak refuses to play ball with the FBI, Stahl turns up the heat on Harlee who lands in the middle of Wozniak's dangerous plan to free himself from the Feds by reeling in a bigger fish. Meanwhile, Internal Affairs Officer Verco applies pressure to each member of the crew to discover what really happened to Donnie Pomp.

Realizing that Stahl will stop at nothing to arrest Julia Ayre, Harlee decides to investigate on her own and determine whether there's any truth in his allegations of Ayers' active business with the mob. Wozniak is confronted with a drug case that forces him to face the darkest demons from his past, his daughter's death, while exposing the origin of his loyalty to Ayres.

The mafia seeks revenge on Harlee by framing her for murder. As Harlee works against the clock - and her own crew - to cover her tracks, Wozniak fights to keep his cop-family together when evidence of an old crime puts pressure on the already splintering team. Stahl cozies up to Cristina, getting one step closer to the truth about Miguel.

Harlee and Wozniak investigate Caroline's murder, putting Harlee and Nava's relationship in an awkward place because she can't reveal her connection to the crime or the methods she will use to solve it. Wozniak focuses on determining which member of his crew is informing to Verco as Loman uncovers a much deeper secret.

Following Harlee's brave confession to the entire crew that she has been informing for the FBI, the team grapples with Harlee and Wozniak's betrayal. With their team falling apart, Harlee and Wozniak come up with a desperate plan to neutralize Bianchi. However, their actions have unforeseen consequences because the Mafia fires back.

Wozniak goes after Bianchi for breaking their agreement. Harlee seizes the opportunity to unite the team around an illegal mission to repay Tufo's brother's debt to a local drug dealer. Stahl heightens the stakes making good on his threat to go after the crew. Wozniak faces the impossible decision to pick between his team and Ayres just as his son, Nate, makes an effort to reunite.

Harlee makes the chilling discovery that someone is texting Cristina as her dead ex, "Miguel." The case of a missing kid leads Wozniak to uncover a local dealer who uses underage mules and reminds Loman of what their unit is all about. The crew gets caught in a brutal ambush.

Harlee and Wozniak lead a manhunt for the gunmen who ambushed the crew, and they unearth the key to taking down Bianchi. The crew bands together against Verco, who has evidence of their corruption. Stahl goes rogue to link Harlee to Miguel's death.

Harlee and Wozniak lead the crew on a dangerous mission to heist Bianchi's secret ledger and take down the mobster once and for all. But the plan takes a tragic turn when the events our heroes set in motion put one of their own in harms way, forcing Harlee to turn to an unlikely source for help.

Harlee helps Nava cover his tracks after a violent encounter, revealing a side of herself Nava's never seen before and putting their relationship in jeopardy. Wozniak faces a ghost from his past in order to take down a new enemy in his present. Stahl gets a critical piece of information in his hunt for the truth about Miguel.

In a dramatic confrontation, Wozniak faces the ally who betrayed him and makes his most difficult choice yet. Meanwhile, Stahl's fanatical plan to take Harlee down for murder finally pays off, forcing Harlee to get dangerously close to the man who's obsessed with her In the end, Harlee and Wozniak's desperate efforts to save themselves and the crew lead to shocking consequences for both.

Harlee Santos, a detective from a tight-knit group of Brooklyn cops with questionable tactics, is arrested by an FBI agent who wants to make her an informant. Co-stars Ray Liotta.

Harlee struggles with becoming an FBI informant while Wozniak suspects every member of his crew. Paranoid that Wozniak's search will lead to her, Harlee suggests polygraphng the entire crew, a plan that backfires. An appeals case sends Wozniak to watch tapes from his first encounter with Harlee, revealing a dark secret from their past. Meanwhile, Espada helps Tess deal with her husband's infidelity.

Harlee refuses to give Stahl incriminating evidence against Wozniak but hands over a fully resolved unoffical investigation that Tess and Espara initiated when they moved a body by Tess' house found to be murdered with a 3D printed gun. Wozniak confronts Harlee who executes a dangerous bluff.

Loman's guilt over the death of an unarmed suspect becomes a liability for the crew, forcing them to test his loyalty. Wozniak sends Harlee on an errand that reveals he has a silent partner in the big score. Wozniak realizes Donny has been withholding information. Harlee feigns cooperation with Stahl, but unwittingly leads the FBI to incrimmating evidence,

Harlee and Tess intercept a heroin shipment from a local drug lord who discovers Wozniak's secret and tries to use it as leverage to get his confiscated drugs back. Harlee fears Stahl's interest in her goes beyond the professional, believing he is invading her privacy, and resorts to spying on him with the help of an old friend. Tess tries to use Espada to get back at her husband.

Wozniak's suspicions land on Saperstein, forcing Harlee to convince Stahl to arrest Saperstein in order to keep him safe. Harlee visits her abusive ex, Miguel, who tasks her with tracking down the man who committed the murder for which he is imprisoned.

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.

After Saperstein's death, Harlee realizes there are no lines Wozniak won't cross and decides to help Stahl's investigation. The crew retaliates against a pair of abusive cops after they harass Harlee's daughter Cristina and her boyfriend. Wozniak makes Loman feel like a part of the unit.

Harlee's collaboration with Stahl (Warren Kole) uncovers Wozniak's secret relationship with Donnie.  Wozniak decides to take charge of the big job after picking up a package that turns out to be a kidnapped man.  A mysterious call to Saperstein's desk forces the crew to face their mixed feelings about their fallen friend and ultimately decide to preserve his memory.

Harlee and Wozniak secure more details on the big score and meet Donnie's silent partner, who reveals himself to be an DEA agent.  They learn the big score is an armored car heist.  Wozniak takes interest in a fellow marine veteran who is suspected of murder under dubious circumstances.

On the day of the heist, Harlee realizes she misplaced her trust in Stahl but it's too late to back down.  Harlee tries to get immunity for her crew as she participates in the heist knowing that it will lead to Wozniak's arrest.  Miguel discovers Harlee's secret.  Loman unwittingly witnesses the heist just as the exchange goes terribly wrong.

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.

Unable to provide Donnie and Linklater to the FBI, Harlee makes a deal with Stahl to exchange her own immunity for that of her crew. Harlee comes face to face with Miguel who reveals his darkest side as he demands to be a part of Cristina's life.