Jackie schemes his way into a new mission as Karen Shimizu tries to get rid of him; Decourcy and Siobhan spar on opposing sides of a legal battle; Grace tries to help her son; Jenny surprises Benny with some rebellious fun; Cathy re-ups her supply.

Struggling to make ends meet after leaving the FBI, Jackie Rohr gets a job offer from his old mentor; ADA Decourcy Ward eyes a promotion; Siobhan Quays takes on a case against a construction colossus; Jenny Rohr volunteers at a community center.

When Victoria Dryden runs away from home, Sinclair sends Jackie to find her. Caysen is after justice for BPD Officer Russ Wallace, who he believes may have been intentionally executed by another member of the Strike Force. The incident sparks a dispute at the Ward home in Brooklyn, where Decourcy is looking after his ailing father. While building a case on behalf of her impaled client, Siobhan experiences an intensifying array of symptoms. Diarmuid Doyle tries to help Jenny.

Vying to become Boston's next DA, Decourcy takes on a murky case involving a murdered police officer. He recruits the help of Caysen, who is becoming increasingly alienated from the officers in his unit. As the Drydens try to solve their Victoria problem, the Rohrs drop Benedetta off for her freshman year at NYU. They return empty nesters but to no peace and quiet. When Siobhan receives a distressing phone call, a dark secret resurfaces.

As Jackie continues his fling with Letitia Dryden, Jenny sets out to get her husband reinstated in the FBI. The pressure on Decourcy mounts when a colleague competing for the position of DA lands a conviction. Caysen testifies at the federal trial of Tony Suferin and is blindsided by the consequences. A threatening interaction offers Siobhan a sense of what exactly she is up against in her fight for the Mendoza family.

An attack stalls the Dryden investigation but Decourcy presses on.