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. Frank gets a personal request from a woman to transfer her son to a safer assignment. Also, Danny seeks to uncover the truth behind the murder of a key witness in one of Erin's cases, and Eddie begins to think about having a child after she and Jamie discover a newborn left outside their precinct.

Erin tries not to feel overpowered as her new boss shadows her at work just as she's trying to get a nervous eye-witness to reveal the identity of who shot her boyfriend. Also, the serial killer who previously held Danny and Baez hostage resurfaces, and when Jaime arrests an intrusive reporter who appears at a series of store lootings, it leads to a standoff between Frank and the Attorney General over the press' First Amendment rights.

Frank takes matters into his own hands to save Gormley's career when complaints against him become public knowledge; Danny and Baez learn to be allies when the transgender community comes under attack.

Frank and Garrett quarrel when Garrett refuses to walk back a quote he provided to a local newspaper. Also, Danny and Baez discover a connection to a feud between local residents and city-sponsored hotels for the homeless while investigating a murder, Anthony is mistaken for a mafioso and Eddie pressures Jamie to take a love language quiz.

Frank launches an investigation after the Reagan family is harassed; Danny and Baez form an unlikely partnership with an informant in order to prevent a murder; Eddie lands in hot water after she defies a direct order.

Jamie and his new intel team officer infiltrate a high-tech car smuggling ring; Frank faces off against the city's transit chief over a program that is causing officer injuries on the job; Eddie asks Danny to help her bust a cop impersonator.

Danny reunites with Mickey Patrick, his childhood friend and a former criminal, who comes to him for help finding his missing fiancee; Anthony surprises Erin with one last stakeout before her run for district attorney.