Atwater and Ruzek go undercover as inmates of a federal prison to solve the murder of a 10-year-old girl.
When Fin's ex-brother-in-law is arrested for attacking a priest, the team work to prove the truth. But the case turns up more than they bargained for.
A shocking ambush at a funeral leads the team into a heated investigation to find the shooters; much to Atwater's surprise, he must rely on someone from his past to help in the investigation, dredging up old memories and revealing new truths.
The life of politician Tommy Caffee (Jason Clarke) gets complicated when his gangster brother (Jason Isaacs) returns home to Providence, Rhode Island.
Atwater's worlds collide when a shooting at the building he owns in Burnside leaves a child dead; Atwater must confront his relationship with his father, Lew, as the brutal case forces them together.