Danny considers retiring until Erin asks for his help with a case involving her ex-husband; Jamie and Eddie pose as a couple; Frank clashes with the new mayor.

Frank receives an order from the mayor to attend a parade honoring a man who served time for conspiring in an attack against the police. Meanwhile, Danny investigates the return of a teen who suspiciously disappeared 13 years ago; and Jamie and Eddie help a young woman they believe is being exploited by a congressman.

Erin’s trial against a notorious human trafficker is jeopardized when the presiding judge is mysteriously found dead. Danny and Baez are put on the case to investigate foul play. Meanwhile, Mayor Dutton opposes Frank’s public safety initiative, but City Council Speaker Regina Thomas devises a plan to help Frank bypass the mayor’s veto.

Danny and Baez work the case of a detective who was gunned down prior to testifying against a career criminal. Meanwhile, Frank personally investigates when Garrett is attacked by a S.W.A.T. team outside his home; and Erin brings in a confidential informant against Anthony’s wishes.

Danny and Baez investigate the murder of a single mother whose ex-husband has a history of violence. Also, Frank deals with the fallout when Mayor Dutton eliminates solitary confinement in prisons, and Jamie’s efforts to save a young woman who overdosed on drugs has unexpected consequences.

A famous basketball player is found dead of an apparent drug overdose. Danny investigates and looks into the victim’s possible ties to a local drug gang. Meanwhile, Erin revisits the case of a man she may have wrongfully convicted years ago; and Frank is approached by Archbishop Kearns regarding an eviction matter that Jamie and Eddie are working on.

A case turns personal for Danny when he works to protect a nurse, Faith Madson, from her violent ex-boyfriend. Also, Shelly Wayne, an acquaintance of Frank's, comes to him with a theory regarding the death of an inmate, and Jamie and Eddie help deliver a baby.

Eddie's judgment is clouded by her past when she arrests a loathed acquaintance from college on questionable charges. Also, Frank is hesitant to mar the spotless record of a member of the force, a decorated U.S. military veteran, who tested positive for marijuana.

Danny and Baez join a narcotics task force to track a drug supplier; Baez comes into contact with drugs and gets an accidental overdose; Jamie and Eddie work to protect a rehabilitated sex offender; Frank forms an unlikely alliance with Mayor Dutton.

Jamie and Eddie ask Erin to drop old charges against a man who bravely rescued a woman from a local hostage situation; Danny and Baez work a case involving car thieves and discover the leader is a mobster they've dealt with before.

When a journalist disappears while working on an exposé about an innocent man serving time for murder, Danny and Baez hope that reexamining the original case will help find her. Also, Frank reluctantly speaks out against an initiative led by Erin's office to consider drug abuse as a disease first, and a crime second.

After Anthony is shot while interviewing a witness for an upcoming murder trial, Erin enlists Anthony's archenemy, Danny, to find out who was responsible. Jamie and Eddie get in the middle of a standoff between a police lieutenant and a developmentally disabled man posing as an officer and Nicky prepares to take the police exam.

When Henry is the key witness on Danny and Baez's case, his meddling pushes Danny's buttons until he leads them to valuable information. Also, Nicky shocks her family by siding with her activist friend, Chrissie, who defaced the NYPD flag at One Police Plaza, and Jamie and Eddie learn a parole officer is taking advantage of his power over parolees.

When a student is shot by a rival gang member in his high school courtyard, Danny and Baez try to get a grasp on the situation to prevent a reoccurrence, but the principal recklessly takes matters into his own hands. Also, Erin tries to help a friend who is mixed up in an illegal gambling ring; and Gov. Mendez tries to frame Frank after one of his top legislative aides is shot by an NYPD officer

Danny considers taking a new job that would ease his financial struggles after investigating the death of a wealthy man. Also, Nicky tries to avoid involving her family when she is sexually harassed by her boss at her new internship, and Garrett advises Frank to regain the public's trust after a rookie cop is caught on video questioning a pedestrian's immigration status.

Danny and Baez investigate the murder of a man who was living a double life with two separate families, and Anthony tries to resist when Erin asks him to help investigate his old partner, whom she suspects of stealing drug money. Also, Frank deliberates between two candidates for the chief of transit position.

After Danny’s brother-in-law, Jimmy, gets caught up with the mob and steals Danny’s credit card, Danny forces Jimmy to take down the mobsters with Baez’s help. Also, Frank has Erin and Anthony investigate if his old partner, Lenny, is truly guilty of a crime and Jamie is approached by Tariq, an officer who wants his help getting reassigned from his undercover assignment at a mosque.

After a woman voices her outrage regarding the NYPD’s inability to find her son’s murderer, Danny reexamines the case, upsetting the original detective, Erin, and Anthony, who didn’t pursue the case due to lack of evidence. Also, Eddie is shot while on duty; Erin and her ex-husband, Jack, face off in court; and Frank contends with an angry police force when Mayor Dutton fails to defend them at a press conference.

When Danny resorts to asking his incarcerated archenemy, Victor Lugo, for help locating a dangerous criminal who escaped from prison, Lugo refuses to assist unless he’s allowed to accompany them on the pursuit. Also, Frank subtly tries to convince Jamie to take the sergeant’s test, and Erin’s plan to go on a date with her ex-husband causes friction between her and Anthony.

Frank locks horns with a data-tracking company when it refuses to unlock a terrorist's phone that may hold information regarding upcoming targets; Erin obtains information about an impending murder from a shady source; a woman kidnaps a baby.

When a series of drive-by murders occur after six wrongly convicted men are released from prison, Danny and Baez wonder if they were orchestrated by the men as an act of revenge. Also, Frank combats the guilt he feels about these innocent men unfairly serving nine years in prison, and Jamie and Eddie find themselves in a life-threatening situation.