Childhood friends Paulie (Ethan Hawke) and Brian (Mark Ruffalo) grew up looking out for each other in their Irish-Catholic neighbourhood in South Boston. Trapped in a cycle of gangs, gangsters and shady crime, they are constantly dodging local turf wars and the watchful eye of an encroaching police detective (Donnie Wahlberg). But with Brian's wife (Amanda Peet) growing increasingly distraught by her husband's lifestyle, will the tried and tested friendship between these two Southies crumble once and for all?