| Director | Troy Duffy |
|---|---|
| Genre | action film, buddy film, drama film, vigilante film |
| Runtime | 110 min |
| Country | United States |
| Budget | $8 million |
| Box office | $10.6 million |
On St. Patrick's Day, a renowned Boston priest is ritually murdered. Father Sibeal arrives in Ireland to inform his nephews the MacManus twins, Connor and Murphy, that someone has copied the style of execution they used eight years earlier to kill Mafia boss Joe Yakavetta. The twins and their father, Noah, realize that someone is trying to implicate them in the priest's killing. In response, the Saints dig up their old gear and weapons and depart for the United States, but Noah stays behind.
En route to Boston aboard a container ship, the twins meet Romeo, a Mexican underground fighter who recognizes them as the Saints. Romeo convinces them to let him join them as their new partner. Hearing a radio broadcast regarding Joe's son, Concezio Yakavetta, they deduce that he must have hired the hitman who killed the priest to draw them out of hiding.
Meanwhile, Boston Detectives Greenly, Dolly, and Duffy are at the scene of the priest's murder. Also there is FBI Special Agent Eunice Bloom, a no-nonsense protégée of the late Paul Smecker, who has been assigned to determine whether or not the Saints are responsible for the murder. Bloom eventually concludes that the Saints did not murder the priest, and begins an investigation to find the real assassin. She and the detectives deduce the killer is Ottilio Panza, working for someone known only as "The Old Man".
Connor, Murphy, and Romeo hit a warehouse that is being used by a Chinese Triad gang to process heroin for Yakavetta. After clumsily killing everyone at the warehouse, the trio hides out with the MacManus' old bartender friend, Doc. They learn that the assassin was an independent contractor and that Yakavetta himself is hiding in the Prudential Tower. Later at the warehouse, Bloom confirms that the Saints have returned.
The twins and Romeo have Yakavetta's caporegime "Gorgeous George" set up a meeting with a group of mobsters at a bar, where they kill them all except George, who is allowed to escape. Panza arrives shortly after and attempts to ambush the twins, but Bloom arrives in time to save them by wounding Panza, who then flees. Bloom introduces herself to the Saints, revealing that she had intended to help them all along in Smecker's place. The group then cleans up the crime scene to make it look as if the mobsters had turned on each other. Later, Bloom reunites the detectives with the Saints, thus bringing them in on their plans.
Yakavetta calls a meeting with his crew, during which the Saints arrive and kill everyone, including Yakavetta. Bloom interrogates Yakavetta's consigliere Jimmy and learns of the Old Man's involvement with Panza. FBI Special Agent Kuntsler takes over the gang murder case, suspending Bloom. Later at the bar, Greenly arrives to celebrate the boys' victory, but is shot and killed by Panza. Noah, earlier having decided to help his sons, unexpectedly arrives to demand Panza tell him the Old Man's location. They engage in a "Russian roulette" stand-off, and after Panza still refuses to answer, Noah kills him.
Noah relates to the group that in 1958 New York, he watched a trio of mobsters brutally murder his father. Aided by his best friend Louie, Noah later hunted down and killed the mobsters. Noah still felt unsatisfied, so Louie reluctantly helped him pick out other mobsters to kill, which is how Noah became "Il Duce". They continued this until 1975, when Louie finally gave Noah up to the police.
Bloom illegally obtains a file regarding Louie's location and gives it to Noah, which reveals that Louie is The Old Man. Anticipating the Saints' arrival at his mansion, Louie has hit men stationed on the grounds. Confronted by Noah, Louie admits that he had deliberately used Noah to eliminate his competition in the Mafia, afterwards giving him up to the police when he was no longer useful. After this, however, the Mafia cast Louie himself out for the same reason. He then helped rebuild the Yakavetta family after Joe's demise and let the Saints take out the rest of the organization so Louie could take control. Louie signals the hit men waiting for the Saints to make their move, but the Saints and Romeo kill them all. Noah suffers a fatal gunshot wound, but kills Louie before he dies. The police arrive and Connor, Murphy, and a seriously injured Romeo are taken to a prison hospital.
Bloom meets with Sibeal, who has arranged to take her to a safe place out of the country to flee FBI prosecution. She discovers that Sibeal has been working with Smecker, who faked his own death and developed a network of support for the Saints and their work. Smecker tells Bloom he plans to break the Saints out of prison. As supporters outside of the prison protest for the release of the Saints, Connor and Murphy see the sea of prisoners in the yard, finding that they will have plenty of work while they wait to be freed.