The story of America's most notorious gangster, Al Capone, starts on the streets of Brooklyn. In 1913, at the age of 14, Capone starts running errands for local gangsters - just one of many immigrants struggling to survive. One day, young Al Capone gets caught in a police raid. He quickly grabs what money he can, evades police, and runs to the headquarters of mob boss Johnny Torrio. Torrio rewards Capone for his quick-thinking. When Torrio recognizes Capone's intelligence and drive, he takes him under his wing. Capone starts working as a Torrio's bookkeeper.
After a few years of grooming Capone, Torrio decides to leave New York for a lucrative business opportunity in Chicago. Torrio passes Capone's mentorship onto mobster Frankie Yale, who runs a bar in Coney Island. But Yale is known for more than running a bar: he's a dangerous, influential hitman for hire.
Unlike Torrio's low profile, business-style of crime, Yale uses violence to meet his ends, and Capone knows that in order to get ahead, he'll need to become an enforcer. Not willing to cross the line yet, Capone loses momentum and stalls, working as a bartender for Yale for years.
One day, while working the bar, he approaches a girl he likes and strikes up a conversation. A man asks what he's doing and pulls a knife on him. He slashes Capone on the face, neck and throat, delivering the famous scars that later earned him the nickname, "Scarface." It takes him months to recover, before he returns to Yale's bar.
Capone begins dating a woman named Mae Coughlin. They eventually marry, and Mae becomes pregnant. Capone knows he isn't earning enough to support a wife and child and asks for more lucrative work from Frankie Yale. Yale tells him to collect a debt from a man named Tony Baratta.
Capone comes across Baratta gambling in an alley with a group of other men. Baratta refuses to make good on his debt. Capone pulls a gun on him and says he's not leaving without the money. When Baratta refuses to give in, Capone shoots him.
In 1919, Capone leaves Brooklyn to move to Baltimore in an effort to escape Brooklyn's mob influences. He works as an accountant for a construction company. Despite having an honest job, Capone struggles to provide the life he wants for his family. In the Spring of 1919, Capone holds a baptism for his son. He asks his childhood mentor, Johnny Torrio, to be the godfather. Torrio says he might be able to find a job for Capone out in Chicago.
In the winter of 1919, Capone decides to take Torrio up on his offer and work in Chicago. Since leaving New York, Torrio has risen up the ranks of the mafia in Chicago, running hundreds of brothels and gambling dens - the most impressive of which is the Four Deuces. Still, he needs to kick up a sizeable chunk of his profits to his boss, "Big Jim" Colosimo. Even though Colosimo owns the largest empire of brothels and gambling dens, he is just one of many kingpins in Chicago's neighborhoods.
Capone keeps Torrio's books and ledges from all of his different illicit businesses. Capone learns about the administrative work of a successful crime syndicate from Johnny Torrio.
On January 17, 1920, Congress bans the selling of alcohol across the country, in what will come to be known as Prohibition. Johnny Torrio has the idea to take over the now-closed breweries -- but they need Colosimo's approval. Capone and Torrio deliver their idea to Colosimo, but he rejects the proposal. In private, Torrio and Capone decide to start their own bootlegging racket, directly defying one of Chicago's most powerful and dangerous men.
When Capone and Torrio's successful bootlegging business becomes harder to hide in the ledger, Torrio becomes convinced that Colosimo is onto them and the only way to save themselves is to kill him.
Torrio brings in the one hitman he knows he can trust: Capone's old boss, Frankie Yale. On June 11, 1920, Big Jim Colosimo is gunned down in the lobby of his cafe. The murder shocks the nation, but with no witnesses willing to testify, the crime is never solved.
Hours after Colosimo's death, Torrio takes over Colosimo's empire and soon expands their bootlegging racket. Torrio and Capone become some of the biggest booze suppliers in the city. But with their new high profile come new risks, and the powerful Irish bootleggers of the North Side set their sights on the new competition.