Frank goes on high alert when a threat to New York City may be imminent following a terrorist attack in the Middle East.

Danny and Baez investigate a possible serial killer who sends a chilling message to Danny. Erin toys with the idea of applying for a judgeship. Frank is in a bind when mayoral candidate Katherine Tucker accuses him of secretly investigating her husband. Eddie faces her estranged father when he winds up in the hospital.

When newspaper reporter Lorenzo Colt is targeted while wearing NYPD gear on a ride-along with Jamie and Eddie, Frank puts Danny and Baez on the hunt for the shooter, who may be out for other members on the force. Garrett contemplates taking another job.

Erin’s attempt to convict a slippery mob boss for an old murder is muddled when a former informant leaves witness protection to provide his old boss with an alibi. Frank finds himself in a departmental war with Commissioner of the New York City Fire Department.

Danny joins the hunt for two escaped convicts after hearing one of them is someone he helped to wrongfully imprison. Gormley criticizes a plan from an NYPD sergeant who Gormley thinks is having an affair with his wife.

When Jamie is caught on camera committing what could be construed as police brutality at a demonstration, Frank is forced to turn the case over to Internal Affairs. Danny and Baez investigate a rape case involving a civil rights attorney who claims the charges were drummed up in retaliation for the investigation into Jaime.

Danny and Baez investigate the theft of the only remaining Mustang that Steve McQueen drove in the film “Bullitt.” Erin is at odds with Frank when she is forced to side with her office after the acting District Attorney orders that a slew of cops be arrested for fixing traffic tickets for their friends.

When Danny and his family are threatened by a serial killer Danny has not been able to apprehend, Linda’s concern intensifies over her husband’s job as well as the state of their marriage. Jamie challenges his superior officer during a hostage situation.

When a homicide case ends in a hung jury, Erin is forced to take over the case and find a missing witness. Jamie and Eddie go undercover as an elderly couple to catch a gang that is terrorizing a neighborhood.

Danny is interrogated by the District Attorney’s investigator when his ex-partner is accused of planting evidence in order to wrap up a homicide case. When radical anti-government activists threaten to publicly burn an American flag, Frank grapples with the limits of free speech.

When Frank’s first partner announces plans to publish a book filled with stories of their early days on the force, Frank worries about his personal stories being made public. When Jamie and Eddie catch a call about a nearby officer needing assistance, the choices they each make will affect their future in the department and their relationship.

When a local mobster is gunned down in his car, Danny and Baez try to get information from the mob’s low-level errand boy they find tied up in the trunk before the gang retaliates. An NYPD officer asks for a new shield number to honor her late father, but Frank is conflicted because it’s the same number as his deceased son's.

A respected, recently retired NYPD lieutenant is accused of shooting potential muggers on the subway. Baez and Danny try to arrest a drug dealer responsible for a murder Baez witnessed as a child.

Four women from a brothel admit to murdering their evil boss — Danny and Baez must figure out the real killer. Frank and his priest argue over mercy in the Catholic Church. Nicky gets in drug trouble with her friends but no one takes the blame.

Erin finds it hard to deal with guilt after a man she set free is suspected of killing a policeman. Frank and Mayor Poole clash over Frank's reappointment as commissioner.

Linda needs Danny and Baez's help after a co-worker has difficulties with an angry ex. Erin's former mentor has been giving out unfair sentences following the death of his wife.

Jamie and Danny disagree about how to handle a reckless NYPD rookie, who is the son of Danny’s friend. When Erin’s investigator gets roped into a bad investment by his cousin, she offers to look into it.

Frank and Danny work together to help Nick Constantine, a rehabilitated ex-con who Frank put away years ago, when Constantine becomes involved in the murder of an old enemy. As Erin prepares for a murder trial, she learns the prosecutor who previously handled the case is withholding the location of the alleged killer so she can interview him on her popular podcast.

While hunting for a robbery crew on a wild crime spree, Danny and Baez partner with Detective Jimmy Mosley from another precinct who broke Baez’s heart years ago. When an officer who was acquitted on charges of killing a young boy is up for a promotion, Frank grapples with the decision of moving him up the ladder and risking public outrage.

When serial killer Thomas Wilder attaches a message to his latest victim that taunts Danny, their deadly game of cat and mouse becomes personal for Danny.

When a key eyewitness in a murder trial flees out of fear of retaliation, Erin and Anthony spearhead their own two-person manhunt to find him and convince him to testify. Garrett tries to convince Frank to attend the Police Union party. Danny and Baez take a closer look at a suspicious convenience store robbery.

Frank, the Mayor, Erin and the DA’s office contend with public outrage after a grand jury doesn’t indict an NYPD officer for the controversial shooting of a teenager that was caught on video. When an officer gets shot in a possible case of retaliation, Danny searches for the shooter.