Dublin's criminal underworld is filled with organised crime, drug addiction, squalor and violence that has erupted in post-boom Ireland. Returning to Dublin is Darren Treacy, who had been spending time in Spain while trying to avoid Ireland's Garda, which wanted him for gun possession. When Darren's brother and former gangmate, Robbie, is shot in a drive-by shooting outside Cloverhill Prison, it sets off catastrophic events that spark tension between rival gangs. The Dublin community then must live with the consequences of the ensuing gang war.