The Boondock Saints is a film that captured the vigilante spirit of comic classics like Batman and the Punisher and put it into an every-man package that struck a nerve. Originally given poor reviews and a limited release, the film garnered over $50 million in domestic video sales, and it eventually earned a sequel. The film begins with Irish fraternal twin brothers Connor (Sean Patrick Flanery) and Murph (Norman Reedus) McManus. After a sermon about the fate of Kitty Genovase, the two brothers go to work and then head out to a bar to celebrate Saint Patrick's Day. They get into a bar brawl with low-level Russian mob thugs, who decide to hunt the brothers down the next day for vengeance. Connor and Murph manage to kill the enforcers, after sustaining heavy injuries, and turn themselves in, rightly claiming self defense. They stay in jail for the night and have a premonition from God that they are there to destroy the wicked and violent. This revelation causes the brothers and their friend, low-level mobster David Della Rocco, to get involved in a spree of violent reprisals against the mob, both Russian and Italian.
As the brothers are hacking their way up the chain of command, FBI agent Paul Smecker (Willem Dafoe) is putting the pieces together and figuring out what's going on. The mob arranges for the release of Il Duche, a world-renowned hitman played by Billy Connolly, to take out the brothers before they kill anyone else in the family. Smecker has a crisis of faith and decides that he'll help the brothers do what he cannot, as an agent of the law. This leads to a showdown between the brothers and Il Duche, who turns out to be the long-lost father of the twins. Banded together in purpose after the death of Della Rocco, the family makes itself known by executing a high profile mafia boss during his court trial. Then they vanish into the night, with the implication that this is just the beginning.