Suddenly touched by the crime overrunning the streets of Boston, Irish twin brothers Connor and Murphy MacManus (Sean Flanery and Norman Reedus) embark on a journey to cleanse their city of evil with their own brand of vigilante justice straight from the Emerald Isle, one fueled by Catholic ritual and spiritual belief. As the bodies of notorious gangsters hit the floor, one after the other, the brothers become controversial folk heroes in their adoptive community. But eccentric FBI agent, Paul Smecker (Willem Dafoe), is closing in on them fast as the boys deliver vengeance from what many believe is the great and terrible right hand of God. Are they sinners, or are they Saints? You decide.