Frank is put on the spot when one of the mayor-elect's supporters is found dead; Jamie goes under cover at a bar.
Danny must face an internal affairs investigation after shooting a cop who failed to identify himself.
Danny makes a discovery about an attempted bank robber's past; Jamie starts working with a new partner (Monica Raymund).
Erin reopens a rape case Frank worked on 18 years ago; when three teens are murdered, Jackie and Danny can't determine an obvious motive.
Danny tries to investigate a case while having a romantic weekend with Linda; Jamie goes under cover to infiltrate a crime family.
Jamie and Renzulli are injured by a church's security team while responding to a 911 call, and Frank must deal with the fallout.
Jackie goes under cover as a prostitute to catch a serial killer; Erin meets a man at an art gallery.
Jackie and Danny think a young woman was forced to commit suicide; Frank clashes with Mayor Poole over a threat to the city; Henry has a heart attack.
A dangerous ex-mobster helps Danny with cold cases in exchange for leniency for his son; Jamie searches for a secret about the Sanfino family.
When Erin's informant is murdered, she can't help but blame herself for the death and work to help Danny discover who killed him; Frank deals with public backlash against an officer.
Jackie and Danny investigate a murder at a diner, where a witness claims a uniformed officer fled after shots were fired.
Danny and his family have an encounter with a gunman; Frank prepares to say goodbye to a friend he worked with at ground zero.
After a wealthy woman dies of a heart attack, the daughter claims God told her that murder was the true cause of her parent's demise; Frank investigates a rumor about a priest.
When a man's family is beaten and robbed in front of him, the Regans debate how far they would go to protect the ones they love; Frank feels conflicted when a college student is arrested at a rally.
When a family friend, an undercover detective, is murdered, Danny embarks on a relentless search for the killer.
When a reporter friend of Frank's is almost attacked while investigating a story, Danny and Jackie try to find the would-be attacker; Jamie makes headway in his undercover case.
As Erin prosecutes a woman accused of murder, the defendant's attorney is slain, and Danny is asked to investigate; things get heated when Danny is questioned on the stand.
When a weapon linked to a crime is brought into the NYPD's gun buyback program, Danny must decide whether to arrest the suspect or follow the "no questions asked" policy.
The son of a firefighter whose death was ruled a suicide convinces Danny to reopen the case; Jamie worries that press coverage of him rescuing a baby from a burning building will compromise his cover.
When an attempt is made on the life of a witness in Danny and Jackie's care, they realize the task force has a leak; Erin receives a job offer that would have her working with her father.
Jackie and Danny look into the suspicious death of an investor; when the Sanfinos order a hit on Jimmy Riordan, Frank puts Jamie under house arrest.