While at an out-of-town conference, Dr. Mark Burns is murdered and detectives initially suspect a con-artist. Further investigation reveals that Dr. Burns was not the intended suspect. Leading them to believe another doctor is still in danger.
An inebriated high school girl is killed after leaving a party. Detectives track down the cab that drove her home and are soon led to a prostitute with an affluent past. Detectives pit the prostitute against her pimp to see who will talk first.
While Henry works as an investigative consultant for child services, he and Danny butt heads over a case involving a man who is volatile toward his wife. Also, Frank is caught in the middle of an ongoing battle between the NYPD and the FDNY.
After getting a match from an unknown relative from a DNA network, Sean Reagan does some detective work to figure out who this mystery person might be, and Frank gets a personal request from a woman to transfer her son to a safer assignment.
Danny contemplates retiring until Erin enlists him to help her with a case involving her ex-husband. Jamie and Eddie go undercover as a couple, and Frank butts heads with the new mayor of New York City.
Erin's trial against notorious human trafficker Chao Lin is jeopardized when the presiding judge is found dead, causing Danny and Baez to investigate foul play. Also, Mayor Dutton opposes Frank's public safety initiative.
Frank receives an order from the mayor to attend a parade honouring a man who served time for conspiring in an attack against the police. Also, Danny investigates the return of a teen who suspiciously disappeared 13 years ago.
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.
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 tries to save a young woman who overdosed.
When a famous basketball player is found dead of an apparent overdose, Danny looks into his possible ties to a local drug gang. Also, Frank is approached by Archbishop Kearns regarding an eviction matter Jamie and Eddie are working on.