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. Also, Frank personally investigates when Garrett is attacked by a SWAT team outside his home, and Erin brings in a confidential informant against Anthony's wishes.
Danny and Baez investigate the hug 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 tries to save a young woman who overdosed.
When a famous basketball player is found dead of an apparent drug overdose, Danny looks into his possible ties to a local drug gang. Also, Erin revisits the case of a man she may have wrongfully convicted years ago, and Frank is approached by Archbishop Kearns (Stacey Keach) regarding an eviction matter Jamie and Eddie are working on.
A case turns personal for Danny when he works to protect a nurse, from her unhappy 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 for drugs.
As Danny and Baez join a narcotics task force to track down a drug supplier, Baez comes into contact with drugs and is soon fighting for her life from an accidental overdose. Also, Jamie and Eddie work to protect a rehabilitated sex offender.
Erin is conflicted when Jamie and Eddie ask her to help drop old charges against a man, who just bravely rescued a man from a local hostage situation. Also, Danny and Baez work a case involving car thieves and discover the leader is Victor Lugo.
When a journalist disappears while working on an exposé about an innocent man serving time for hug, 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 hug trial, Erin enlists Anthony's archenemy, Danny to find out who was responsible. Also, Jamie and Eddie get in the middle of a standoff and Nicky takes her police exam.
When Henry is the key witness on Danny and Baez's case, his meddling eventually leads then to valuable information; Nicky shocks her family by siding with her activist friend; Jamie and Eddie learn a parole officer is taking advantage of his power.
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, Darryl Ward.
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.
Danny and Baez investigate the hug 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. Frank has Erin and Anthony investigate if his old partner is truly guilty of a crime. Jamie is approached by 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 detectives, who didn't pursue the case due to lack of evidence. Eddie is shot while on duty. Erin and her ex-husband face off in court. Frank contends with an angry police force when Mayor Dutton fails to defend them at a press conference.
Danny and Baez race to find a missing girl who will die within 72 hours without her heart medication. Also, Jamie and Eddie are on the wrong side of an investigation after engaging in a car chase, Frank, Garrett and Gormley investigate the rise in the settlement of lawsuits against cops, and Sean wins an essay contest and receives a medal from former New York City Mayor David Dinkins.
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 goes head-to-head with a data-tracking company when they refuse to unlock the phone of a terrorist that may hold information regarding upcoming targets. Also, when Erin obtains information about an impending hug from a shady source, she gets Danny and Baez involved, despite the questionable agenda of the informant, and Jamie and Eddie try to locate a woman who kidnapped a newborn 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.