After mistakenly killing mafia criminals, two Irish brothers become vigilantes and consider themselves on a mission from God. As they start taking down mafia gang members, a detective tries to uncover who's behind those killings.
While leading a peaceful life in Ireland, the MacManus brothers find out that some mobsters have killed a Catholic priest in Boston and framed them for the crime, upon which they decide to return to Boston to exact vengeance on the real culprits.