The film chronicles the events leading up to one of the most infamous criminal acts in American history. Set during the late 1920s, it follows the intense rivalry between Al Capone and George "Bugs" Moran, who are vying for control of Chicago's lucrative bootlegging operations. As tensions escalate, Capone employs Jack McGurn, a hot-headed enforcer, to devise a plan that will eliminate Moran and his North Side Gang, solidifying Capone's dominance. The narrative dives into the intricate details of organized crime, filled with betrayals, politics, and the inner workings of gangster life that end up sowing seeds for an inevitable violent confrontation.

Facing increasing pressure from law enforcement and other rival gangs, both Capone and Moran take escalating steps to protect their interests. While Moran attempts to outmaneuver Capone through strategic alliances and political connections, Capone's gang infiltrates Moran's operations, gathering crucial intelligence. As trust erodes and desperation mounts, the film culminates in the carefully orchestrated violence that forever changes the landscape of organized crime. Through compelling character portrayals and gritty atmospheres, the story portrays a time when criminal empires clashed with unrestrained ferocity, exploring the paths that led key figures to a turning point in gangster history.