Tired of the crime overrunning the streets of Boston, Irish Catholic twin brothers Conner and Murphy are inspired by their faith to cleanse their hometown of evil with their own brand of zealous vigilante justice. As they hunt down and kill one notorious gangster after another, they become controversial folk heroes in the community. But Paul Smecker, an eccentric FBI agent, is fast closing in on their blood-soaked trail.

For the last 8 years the brothers have been living with their father on a sheep farm deep in isolated Ireland. One day their uncle tells them that they have been framed for the murder of a Bostonian Catholic priest. The boys must return to Boston to not only clear their names but find the men who framed them.