After a terrorist attack takes place in the Middle East, a threat to New York may be next, putting Frank on high alert.
Danny receives a chilling message from a possible serial killer; Erin considers applying for a judgeship; mayoral candidate Katherine Tucker (Mary Stuart Masterson) thinks Frank is secretly investigating her husband.
When a newspaper reporter (Zachary Booth) is targeted while wearing NYPD gear during a ride-along, Frank thinks the shooter is targeting cops.
One of Erin's informants leaves witness protection to give his former boss an alibi; Frank and the New York City fire department commissioner get into a war.
Danny joins the search for two escaped convicts after learning that one is someone he helped wrongfully imprison.
Camera footage appears to show Jamie committing police brutality at a demonstration; a civil rights attorney claims a rape case includes drummed up charges.
A famous car from a classic film is stolen; an order from the acting district attorney puts Frank and Erin at odds.
Linda is concerned when an elusive serial killer starts threatening her, Danny and their kids; during a hostage situation, Jamie challenges a superior officer.
DA investigator Anthony Abetemarco (Steve Schirripa) helps Erin when she is forced to take a case from a colleague, ADA Kelly Blake (Diane Neal); Eddie and Jamie pose as an elderly couple in order to catch a gang.
Danny's former partner is accused of planting evidence in order to close a murder case; anti-government activists threaten to burn an American flag.
Frank worries when his first partner announces plans to publish a book containing stories of their early days on the force; Jamie and Eddie face choices that will affect their futures in the department and their relationship.
A mobster is found shot in his car and his low-level errand boy is tied up in the trunk; an NYPD officer asks for a new shield number -- the same number as Frank's deceased son Joe.
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.
Multiple women take credit for murdering the man they worked for; Frank and his priest clash over how to deal with a boy who has been stealing from the church; Nicky gets into trouble.
Erin struggles with guilt when a man she set free is suspected of killing a cop; Frank and Mayor Poole face off regarding Frank's reappointment as commissioner; a police officer disappears.
Linda asks Danny and Baez for help when a co-worker has trouble with an angry ex; Erin's former mentor, a judge, has been handing out unfair sentences since the death of his wife; Frank deals with an outspoken city council speaker (Whoopi Goldberg).
Jamie and Danny have different opinions on how to handle a reckless rookie; Erin tries to help Anthony after he's conned into making a bad investment.
Frank and Danny try to help a rehabilitated ex-con when he becomes involved in the murder of an enemy; a prosecutor withholds the location of an alleged killer from Erin as she prepares for the trial.
While hunting for a gang of robbers, Baez teams up with a detective with whom she shares a romantic past; an officer acquitted of killing a young boy is up for a promotion.
An investigation becomes personal for Danny when a serial killer attaches a message for him on his latest victim.
When a witness in a murder trial flees out of fear of retaliation, Erin and Anthony must find him and convince him to testify; Garrett encourages Frank to attend the Police union party; Danny and Baez investigate a robbery at a convenience store.