Louie Lamarr, the "Napoleon of the Underworld" in the eyes of Chicago's papers, is a young gang leader whose ruthless efficiency makes him the hidden boss of the entire city. He forges a classic protection racket: gangs pay him a cut, he draws territorial lines, he makes good on losses, and he punishes breaches with deadly force. The result is a fragile peace on the streets and enormous profits for everyone involved. Most are content, though not all. Rocco craves the top slot, and Pat O'Grady — an honest police chief who has known Louie since he was an orphaned street kid — keeps a wary eye on the power and its consequences. Louie also cares for a younger brother, Jackie Lamarr, who attends a strict military boarding school in another city. Jackie remembers hunger and hardship but is proud of his brother, even if he knows little of his criminal empire.
Louie meets Doris Ricarno and almost instantly falls for her, only to discover that she is secretly in love with Louie’s closest ally, Steve Mileaway. The tension between affection and loyalty complicates Louie’s ambition to step back from the rackets while still keeping his loved ones safe. Doris’s affection for Mileaway adds another layer to a web of loyalties that might not survive a coming storm. Louie hopes for an exit, a clean break, and a retirement that doesn’t expose his kin to danger. Before long, a last meeting with his inner circle is arranged, a farewell that includes a visit to Jackie, then a march toward Florida where the couple intends to start anew.
During a family dinner at Jackie’s school, the Major hosts the cadets at the head table. Louie envisions a future where his brother could become a Napoleon of his own sort, but the Major counters that their real aim is to turn boys into good citizens. When Louie proclaims that war is a grand racket, the Major retorts that it is big, but “cruel and profitless,” a remark that gives Louie reason to pause and reflect on the true cost of his dreams.
With Louie’s charisma fading from behind the scenes, the organization begins to crumble. Mileaway explains that he has bombarded Louie with letters and telegrams, but Louie refuses to respond — he does not want Doris or Jackie dragged into the racket. What Louie does not realize is that his revelation about Jackie has already set forces in motion. A violent gang war erupts as a consequence.
In Florida, Louie tries to escape the tension by golf and a moment of levity—until a tire blows out and he drops to the ground, laughing at the absurdity of it all. Mileaway calls, and Doris tells him Louie has become an awful dud. He spends five hours a day drafting his memoirs, seeking a record of a life that feels less and less controllable. When he forgets a club, Doris hands him the phone and he asks whether she might be “one of them,” hinting at the deeper questions about loyalty and love.
To pull Louie back in, the gangsters mastermind a bold kidnapping plot aimed at Jackie outside an ice cream parlor. The ruse fails when Jackie, too perceptive, bolts from the car and flees into the street, only to be struck by a truck. The three cadets who accompanied him identify the would-be abductors for Captain Pat O'Grady, and the wheels of tragedy begin to turn. Back in Florida, Louie completes his book and awaits a publisher’s call, while a telegram from Mileaway arrives to relay urgent word: Jackie has been hurt. The final line of the manuscript reads, > So this concludes the life of a gangster and begins the life of a man. Finis. A visiting literary opportunity arrives as well, but Louie remains stoic, telling Doris to deliver the message that it is “not done yet.”
A visit to a famous plastic surgeon, Dr. J.W. Johnson (as portrayed by Dr. J.W. Johnson), follows. Louie shows a snapshot of Jackie and asks if the surgeon could repair his brother’s face; the doctor answers that he would need to see the patient, and Louie notes that the patient is at Morse Brothers Undertaking Parlor. Jackie is laid to rest with military honors, and Louie’s ward of vengeance tightens its grip as he swears revenge on Gimpy and Midget, two enemies identified by the gang’s survivors. Gimpy and The Midget become targets as Louie returns to the city with Mileaway by his side.
O’Grady confronts Louie with a stark choice: do not flee town, or face consequences. The two men share a drink, and O’Grady eyes the truth in the mirror: Mileaway and Doris are together in spirit, a fact that cannot be ignored. Louie acknowledges that wealth can bring happiness, yet he recognizes that it could not have introduced him to Doris without the money. O’Grady says nothing as he contemplates the consequences of a world where such alliances exist.
Louie sends Mileaway and Doris off for the evening, then faces the Midget himself. “Where do you want to go?” Doris asks, half-teasing, “I could think of a thousand places if you weren’t married to Louie.” She slides off her ring and places it in Mileaway’s hand, leaving the question of allegiance open as Louie leans in for a kiss and the scene fades.
In the ensuing showdown, Louie awaits the Midget in a dry-cleaning shop, while the Midget’s bodyguards wait on the street. A signal triggers a chorus of revving engines as trucks warm up and backfire, and the bodyguards scatter. Louie washes his hands at a filthy sink, and three trucks pull away, leaving chaos and a plan in motion.
At 3 a.m., Mileaway and Doris return to find O’Grady waiting to arrest Mileaway for killing the Midget. Louie is already in jail. Mileaway endures the third-degree interrogation, but finally confesses to the Midget’s death—Received as self-defense, he earns five years and hopes to regain his freedom. Louie, meanwhile, remains jailed for Gimpy’s murder, and Mileaway’s confession does him little good. Louie thanks Mileaway for the gesture and murmurs, “What a friend,” as O’Grady remains silent.
From his cell, Louie reads a personals ad and feigns illness to engineer a breakout. He hides in a dingy room decorated with Napoleon posters—Napoleon, his enduring hero—before contacting a street paper boy to fetch groceries. The boy mentions he has met O’Grady, adding another layer of danger to Louie’s schemes. O’Grady arrives at the door, unarmed but with grave news: the breakout was orchestrated by Louie’s enemies, and two mobs lie in wait to finish him. He is warned that the only way out is to stay hidden in place and that Milesaway would protect Doris when the time comes. O’Grady departs with a grim vow that Louie will be seen again in 30 or 40 years.
A final gesture of friendship arrives in the form of a last supper from the men—steak with a lit cigar—left on the table beneath a Napoleon poster. Louie places his gun on the bed, fixes his tie and fedora in the mirror, then glances once more at the Napoleon canvas before closing the door. The only sound that follows is the jarring finish of machine guns.
