Childhoods of Al Capone, the future ambitious gangster who'll try to become the crime boss of the prohibition era Chicago, and Eliot Ness, the future head of "The Untouchables", a team of incorruptible agents formed to stop Capone.
Capone and his allies start running the show and earning top dollar from booze smuggling. Ness becomes the head of the newly-formed Untouchables and he and his law-enforcement agents start working on Capone's downfall.
Ness' team hits Capone's operations hard. One of the raids ends in a shootout and two civilians are killed in crossfire. This leaves Eliot worried that things might escalate out of control if the raids continue to be violent.
The head of a local worker's union that's on strike is approached by Capone, who offers him help in the battle for his union members' rights. Ness warns the man that offers from scheming Capone always come at a heavy price.
In an effort to catch the child-killer as soon as possible, Ness agrees to a temporary alliance with Capone. However, Capone has no intentions of giving the killer up to the police. If he catches him first, he will kill him.
Capone orders Frank Nitti to sponsor a nice low-tier Irish boxer and family man Tommy Dolan. Dolan starts winning fight after fight, not realizing they're all fixed. The public loves him but Capone plans to cash in on him.
When Capone tries to expand and take over the numbers racket (a form of illegal lottery) in Chicago's South Side, Ness has no choice but to make a temporary alliance with the current numbers kingpin there in order to stop Capone.
There's a new player in town - the moonshiners. When they cut into Capone's profits, he has no intention of tolerating competition, but they won't back down either. Instead, they propose a one-on-one showdown at sunrise.
Ness finds out that Capone is trying to form an alliance with the heads of the New York mafia, Lucky Luciano and Meyer Lansky. He must do whatever it takes to stop this and some bad publicity in the press might help.
Having no allies within the corrupt Cuban regime, Ness and his team get in touch with the Cuban rebels who are trying to overthrow the president and his government. If they succeed, Capone's plan to smuggle liquor from Cuba is D.O.A.