In early '90s Boston, FBI agent Jackie Rohr works within the corrupt culture, but Decourcy Ward, the new Assistant D. A., wants to uproot the system; after an armored car robbery, the two men find themselves in a possible alliance.

After an eventful Sunday at church, Decourcy finds out he has a powerful new enemy in town -- one that puts his wife Siobhan in an awkward position; Jackie is stirring up trouble in his own home, and his distrustful mother-in-law, Rosa, is onto him.

Jackie searches for his absent informant; Jenny revisits her passion to become a teacher; Decourcy works up a plan to overcome the town's infamous "Code of Silence" and get a few suspects to talk; Jimmy skips town to visit his kids.

Jackie strong-arms Jimmy to get a step closer to finding the armored truck guards; Decourcy rattles a suspect called to testify before the Grand Jury; Siobhan learns something unsettling about a leader of the Coalition.

Jackie and Decourcy continue to hunt down the weapon connected to the Revere robbery; a local reporter gets a tip about a story that could lead her down a treacherous path; Siobhan questions whether doing what is right is ultimately what is best.

Decourcy is a step closer to connecting the stolen guns to the Revere robbery when an insider agrees to talk; Jenny is no longer able to ignore Jackie's indiscretions after they show up on her doorstep; money problems worsen for the Ryan family.