As Decourcy prepares to take Sinclair Dryden to trial, despite pushback from the Suffolk County DA, Jackie tracks down a key witness. Siobhan reaches a settlement on behalf of the Mendoza family, but her moment in the spotlight is cut short. Caysen is offered a second chance by a loved one. Reckoning with the rifts in her own family, Jenny meets her long-lost half-brother.

As Jenny grows closer to Diarmuid Doyle, her unwitting husband Jackie is released from the hospital — and he's after revenge. Siobhan calls on Decourcy for help cornering Needham Industries as she fights to expose the corporation's malfeasance. After a break in the case against Sinclair Dryden, the DA's office bumps up against an unforeseen obstacle.

Jackie shows a glimpse of vulnerability when a violent attack stalls the Dryden investigation, but Decourcy presses on, tracking down a list of Sinclair's potential victims. Caysen is formally brought on as an investigator in the DA's office, where he must navigate competing interests. Siobhan weighs risking everything she has built to reveal the truth about her past. Jenny's suspicions are reinforced.

With the evidence against Sinclair Dryden piling up, Jackie takes action. As Decourcy fights to prove Curtis Whitaker's innocence, Caysen, who is desperate to clear his own name, entertains a compromise. Siobhan makes headway in her case against Needham Industries but is set back when a reporter comes asking questions. Jenny meets with a lawyer to discuss her father's lawsuit.

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.

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. 

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 remedy what has been bothering her, but his plan backfires. 

Struggling to make ends meet after leaving the FBI, Jackie Rohr gets a job offer from his old mentor. The perks are enticing, but Jackie has no idea what he's getting himself into. ADA Decourcy Ward eyes a promotion but is diverted by some bad news which lands him back in Brooklyn. Siobhan Quays, having left her prestigious law firm for a position at the ACLU, takes on a case against a construction colossus. Jenny Rohr begins volunteering at a community center where she runs into a familiar face. Season premiere.