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.

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.

Jamie must deal with the emotional consequences of his actions on the job. Meanwhile, Erin questions Mayor Poole on the witness stand.

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 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.