When Danny intercepts a shipment of several million dollars that was heading to a drug cartel in Mexico, he becomes a target when they come back for revenge. Also, Jamie works independently to track down a serial killer who preys on the elderly, and Mayor Poole confides in Frank that he plans to retire.

Danny and Baez team up with two Russian operatives to search for a dangerous Russian man who entered the U.S. on a diplomatic visa. Also, Frank gets involved in a sensitive case involving Archbishop Kevin Kearns, and Erin and Anthony scramble to find out who tampered with evidence in one of their cases.

A witness in a former case of Erin's, asks her for help shutting down a drug operation in his apartment building, she makes it her mission to make the building safe for his family. Also, while investigating a teen's suicide, Danny and Baez uncover information that suggests the death was a homicide, and Frank looks into potential misconduct in the Mayor's office.

Erin faces off against her ex-husband in court when he represents the person she is attempting to convict of murder; a mother accuses the NYPD of being negligent in solving her son's murder; Jamie rides with a new partner.

An ex-NYPD officer goes missing the day after she reveals to Danny her plans to make amends to the woman she and her partner wrongfully convicted years ago; Frank faces a dilemma when one of his peers refuses to retire.

Jamie and Eddie suspect foul play when they respond to a distress call from a woman having an allergic reaction to her lifesaving medication, and learn that her husband is an EMT assigned to take her call, but didn't respond. Also, Erin learns that a man she convicted years earlier might be innocent of the crime, and Frank handles a PR crisis in his department when an exposé on Garrett Moore is published.

When Linda's brother, Jimmy, gets into trouble with the mob, he begs Danny to help him stay safe until it blows over. Also, Frank faces a public relations nightmare when the lawyer of a wrongfully arrested man demands that NYPD officers' disciplinary records be made public, and Nicky goes on a ride-along with Jamie.

While investigating the murder of a man who killed a mother and son years earlier while driving drunk, Danny and Baez are torn between doing their job and finding justice after discovering the connection between the suspect and the victim. Also, Anthony is conflicted when Erin asks him to wear a wire to incriminate his old friend who is involved with the Russian mob.

A parole officer's romance with an ex-con leads to a possible cover-up in a gang leader's shooting. As Danny and Baez investigate the murder, Frank tries to halt further violence by talking to a rival gang leader who once killed a police chief.

When diplomatic immunity complicates a child abuse case for Danny and Baez, Frank intervenes, despite not having jurisdiction on the case. Also, a robbery occurs while Eddie and Jamie are on a double date with Eddie's boyfriend and his sister, and they are forced to step in.

When Danny accepts a side job as a bodyguard for a recently released ex-con who took the fall for someone else, he uses the opportunity to go after the real criminal. Also, Gormley's wife, Sheila, asks Frank to give Gormley a bigger command position, and Jamie and Eddie witness a lovers' quarrel between two cops that leads them to reflect on their own complicated relationship.

When Eddie and Jamie become overly involved in a complicated adoption case between the birth and adoptive parents, they ask Erin to help them settle the dispute without going to court. Also, Frank looks into reports of NYPD cadets cheating on their psychological exams, and Danny learns that Jack plans to enlist in the Marines after graduation.

When the son of Frank's most outspoken critic in the African-American community, Reverend Darnell Potter, is killed, Potter must put aside his contentious relationship with the Reagan family in order to get justice for his son. Also, Erin and Anthony investigate when a convicted felon's cause of death is inconsistent with injuries he sustained during a prisoner transport van accident, and Jamie learns that a mugger he shot in self-defense is the son of an NYPD officer.

Frank is left with minimal information to find a missing boy when a conflicted priest who could help won't break the seal of confession. Also, Danny and Baez investigate the death of a prominent New York City socialite with a secret life, and Jamie and Eddie attend a wedding together.

After Emily Harrison tells Danny and Baez she's concerned her abusive ex-boyfriend will repeat his behavior with his new girlfriend, Emily becomes the prime suspect when he's murdered. Also, Eddie gets jealous when Jamie lets a young woman crash at his apartment, and Frank must decide how to discipline a sergeant after he fails to intercede during an armed robbery while off duty.

When a key witness in Danny's case is killed just before testifying, Erin angers Danny by enlisting Anthony to help him find the killer. Also, Robert Lewis tries to force Frank to publicly support the Attorney General's investigation of the use of excessive force by police, and Eddie and Jamie get the call for an attempted suicide.

As Frank contends with a whistleblower within the NYPD who claims to have evidence of abuse of power in the organization, Danny and Baez investigate the case of a woman who was struck by a car under suspicious circumstances.

Erin and Anthony try to prevent the deportation of a prominent community activist, Coryna Garza, who isn't a citizen, and Frank must decide if the NYPD will participate in the U.S. Marshals' high-profile raid of a local gang.

Intent on bringing justice to Lieutenant Gormley after he is beaten by a mob outside his home, Danny and Frank enlist the aid of Detective Anthony Abetemarco, who has a personal connection to the neighborhood where the attack occurred. Also, Eddie and Jamie witness a dishonest arrest, and Danny searches for a witness to testify against a dangerous gang leader.

Danny and Baez are determined to get justice for a traumatized young woman who was held hostage, despite her resistance to press charges. Also, Frank deals with a PR nightmare when a prominent NYPD fundraiser is spotted cutting through Manhattan traffic in a fake police vehicle, and Jamie is offered a job as a technical advisor on a television show after working with the TV and Film unit.

Danny and Baez investigate the death of an elderly woman who was shot in her home by a stray bullet. Also, Frank faces ridicule from his department when he disciplines a disrespectful cop, and Erin steps in to help her detective, Anthony, find a legal solution to a case that's personal to him.

Evidence against Danny surfaces when the attorney general's office reviews his shooting of a serial killer. Meanwhile, Jamie and Eddie deal with a high-profile drunken driver; and a slain cop's widow asks Frank for a favor.