A dangerous criminal from Danny's past comes back to seek revenge and kidnaps Jackie. Meanwhile, Jamie meets his new partner, while a young officer is shaken after he accidentally shoots an innocent man.
A woman recants a domestic-abuse claim, but Danny and Jackie continue to investigate the situation. Soon they uncover the woman's secret affair with a powerful politician who's friends with Frank. Meanwhile, Linda returns to the workforce, causing chaos at home.
Danny believes a serial killer is on the loose when two separate murder victims are identified as members of a group charged with a gang rape. Meanwhile, Erin’s ex-husband, attorney Jack Boyle, resurfaces in her life as they face off in court.
Danny and Jackie set out to investigate the murder of a bride on her wedding day in a drive-by gang shooting. However, they are pulled off the case and assigned to the protection detail of a Central American president, who they believe is a target for assassination. Meanwhile, Jamie questions his partner Vinny’s methods when he performs an unjustified stop.
Shortly after Frank awards a detective with the Medal of Valor for his undercover work for the NYPD in Malaysia, the detective is taken hostage by a Malaysian drug lord whose brother he helped put in prison. Meanwhile, Henry goes on a ride-along with Jamie and has a different method of getting the job done.
When Erin's key witness, an infamous photographer, is nearly killed in a hit and run, she arranges for Danny to work protection detail to safeguard him. Meanwhile, Jamie and Vinny bust a drug operation.
When a knife-wielding attacker dressed as Baron Samedi, the Spirit of Death, stabs a man in costume on Halloween, Danny enters the world of voodoo. Meanwhile, DCPI Garrett opens up to Frank about a dark secret, and Erin and Nicky take Jack and Sean trick-or-treating.
Danny arrives at a college campus to find a murdered student, who was thought to be dealing drugs. Meanwhile, Jamie has a life crisis when he reconnects with a former law school classmate and Erin must learn to give Nicky some freedom.
When Danny and Kate come up empty-handed with leads for a shooting, Linda helps make a break in the case when she overhears the victim telling his priest who is responsible. Meanwhile, Henry is mugged at an ATM, which sends Jamie into a rage as he tries to track down the assailant.
When two motorists driving gas-guzzling cars die at the hands of a sniper, Danny and Kate are put on the case of what the city believes is the work of a radical environmental serial killer. Meanwhile, a bicycle accident sends Danny’s son Sean to the hospital with a life-threatening injury.
When a man with multiple rat bites is thrown from a moving car, Danny works the case to find out why and who was trying to send a message. Meanwhile, Frank must be diplomatic when dealing with a bigoted radio host who will be broadcasting from New York City.
Before a Hasidic Grand Rebbe passes away, he chooses his youngest son to succeed him. But when the new appointee dies suddenly, Danny investigates the oldest son and others within the Hasidic community. Meanwhile, Henry reveals a family secret to Frank.
When a 10-year-old boy is the victim of an incident in the projects, Danny’s heated approach to the case lands him in anger management class. Meanwhile, Frank navigates the politics of the State Department and the Turkish Government in order to help a young Turkish woman avoid persecution.
Erin and Danny investigate a cold case of a girl who was attacked by her rich and powerful boyfriend, who was never convicted. Meanwhile, Jamie’s friend brings a lawsuit against Danny’s friend after an injury at a pick-up basketball game.
When an off-duty cop tries to stop a bank robbery, he is disarmed by the "Bonnie and Clyde" robbers who take his gun and wound an innocent bystander. Meanwhile, Frank considers getting romantically involved with a woman from the ACLU who happens to be Erin's acquaintance.
When the same tragedy occurs to people who don’t appear connected, Danny must find what they have in common and who is responsible. Meanwhile, Frank helps an old friend come to terms with his alcoholism.
When a devoutly religious young woman is found murdered in a cemetery, Danny questions her family who is shocked to learn that she had a secret relationship.
When two Wall Street brokers are killed in drug deals, Danny looks to question a wounded accomplice at the hospital but he is stopped by Linda, who won’t let Danny see him until after surgery. But when the accomplice dies during the procedure, Danny and Linda battle over the judgment call.
When Danny finds a disoriented man in a park covered in his girlfriend’s blood, he finds it hard to believe that the man has no recollection of the night’s events until they find a strong narcotic in his bloodstream. Meanwhile, Jamie gets into trouble when he helps an off-duty officer cover up his intoxication after he apprehended an armed robber.
Danny blames himself when a young woman commits suicide because he had made a promise to her in the wake of her parents' deaths. Meanwhile, violence involving a gang at a housing project erupts and affects the Reagans.
As the Reagans rally together to take down the leader of the gang responsible for the murder of someone close to them, Danny looks to the gang leader’s girlfriend to lead them to him. Meanwhile, Frank is left reeling from a second loss.