When Capone orders a hit on the Untouchables, Frank Nitti murders the accountant agent and the witness in the police station, and they plan a hit on Ness's home. Irate, Ness confronts Capone at the hotel.
Back at the safehouse, Ness is about to give up when Malone has one last idea - to get the whereabouts of Capone's bookkeeper, Walter Payne, from the Irish police chief. Jimmy meets the Chief, and tells his old friend that he will lay bare all his secrets if he doesn't spill info on the bookkeeper.
Nitti is sent to 1634 Racine to take out Malone. His man stalks the building. But ... he was just like a wop to bring a knife to a gunfight. Jimmy chases him. Nitti waits with a machine gun outside, fires about a hundred shots into him, and leaves him for dead. Jimmy crawls through his house.
Capone is at the opera and rejoices at the news. Ness gets to his old friend just before he dies - and learns of the time and train that Payne will be taking.
Ness and George Stone get to the station and wait. Finally, just before the train is to leave, Payne and Capone's bodyguards enter. They don't recognise Ness as he is helping a mother lift a pram up the many stairs. Ness recognises Payne - and the gangster with the broken nose is about to warn the others. Ness unloads his shotgun and the shootout begins. Meanwhile, the mother with the annoying baby gets in the way - Ness knocks the pram which rolls down the steps.
Sailors (and other passengers out of nowhere) get in the way too, while one gangster seems determined to shoot the baby.
At the bottom, Stone manages to slide across the marble to stop the pram - and take out another ruthless bad guy. One remaining gangster holds Payne hostage. Payne tells Ness he will testify - so Ness asks George to take the gangster out.
Payne testifies about Capone's income tax fraud - of $1.3million! Capone is surprisingly cocky. He is handed a sheet of paper by Nitti (who I'm sure is Dyson Frost from Flash Forward!). Ness spies that Nitti has a gun. The court policeman asks Nitti to step outside. Although carrying a gun, he seems clean. Ness takes the man's matches - and we see "1634 Racine" on the card.
Nitti backs away with the gun - and shoots the cop. Ness chases him up to the roof. He finds Nitti trying to escape down a rope, and he surrenders. Nitti goads him about Malone - so Ness throws him off the roof.
Stone finds the sheet of paper on Nitti's coat with the names of the bribed jurors. The judge won't accept it, so on a hunch Ness asks for time alone with the judge. Back in the courtroom, the Judge reluctantly asks to swap the juries. When asked, Ness says he told the judge he would reveal that his name was also in Capone's ledger. Capone's lawyer changes the plea and Capone gets 11 years. Ness walks up to Capone, taunts him and tells him "here endeth the lesson!"
Back in the station Ness collects his newspaper cuttings, and hands Malone's lucky medallion to Stone. Outside, Ness is a hero again. A reporter asks him what he will do if Prohibition is lifted. Ness tells him he'll have a drink.