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.

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.

Frank causes family tension when he assigns Jamie to guard Danny after a hit is put on him; Frank tries to stop his grandson from seeking revenge after he’s attacked; Eddie gets a hostile new partner.

Frank contends with public outcry to defund the NYPD School Safety Division, after a physical altercation between a school officer and a student goes viral; Danny and Baez help a father track down his missing ex-wife and daughter.