In 1912 Brooklyn, New York, a young Louis “Lepke” Buchalter smashes a jewelry store window, grabs a dozen watches and is apprehended by a policeman. He is sent to the Cheshire Reformatory for boys. After a year, he is released to find his mother has abandoned him. Lepke and his childhood friend, Gurrah Shapiro, attempt another robbery. Lepke is caught and returned to the reformatory. Upon release in 1923, Lepke finds Gurrah celebrating at a pool hall. Gurrah gets Lepke a job working for crime boss, “Little Augie,” who hires Lepke as “muscle.” One day, a garment factory owner refuses to pay Augie an increase in his protection payments. Without waiting for orders, Lepke grabs the man, throws him out a window, and informs Augie he will no longer have trouble collecting his money. A few years later, Augie and Lepke argue about extorting money from an up-and-coming politician. “Lucky” Luciano, an Italian mobster, agrees with Lepke that having a politician owing them a favor could be useful. After Augie tells them to shut up, Luciano suggests to Lepke that things would be better if Augie was not around. That night, Lepke and Gurrah steal a taxicab and drive to a nightclub frequented by Augie. When Augie steps out of the club, they drive up and shoot him with a Tommy gun. Hoping to distance himself from any further murders, Lepke instructs Gurrah to have gangster “Dutch" Schultz hire Mendy Weiss to kill the witnesses to the murder. Mendy dispatches all three witnesses by stabbing them with an ice pick. Days later, Lepke is at the courthouse to be interviewed about Augie’s murder, but without any witnesses, he is not charged. As he is leaving, he runs into Robert Kane, an acquaintance from the old neighborhood who is now a lawyer. Later, Lepke goes to the attorney’s squalid office and hires Kane to represent him. They are interrupted when widow Bernice Meyer, enters the office. Kane introduces his two clients and Lepke is instantly smitten. After a short courtship in which Lepke meets Bernice’s young son David, Lepke asks Bernice’s father for her hand in marriage. Meyer explains Bernice’s first marriage was not a happy one and he fears her making another mistake. Unaware of Lepke’s criminal activities, Meyer gives the gangster his blessing. A few days later, Lepke chairs a meeting of the New York crime bosses, which includes Luciano and Albert Anastasia. When “Dutch” Schultz demands they assassinate New York City prosecutor Thomas E. Dewey, who is trying to bring him down, Lepke calls for a vote. The eight bosses split and Lepke is forced to cast the deciding vote. Claiming such a high profile “hit” would be bad for business, he votes no. Schultz explodes and declares he will kill Dewey himself. When he leaves, Lepke calls a vote to protect Dewey. The next day, Mendy guns Schultz and his men down in a restaurant. A short time later, Lepke marries Bernice. At the reception, Lepke is annoyed by the arrival of Luciano and Anastasia, who express surprise they were not invited as they and Lepke are now “family.” Years later, Robert Kane informs Lepke he has accepted a job with the Federal Bureau of Investigation (FBI), working in the narcotics department. A disgruntled Lepke arrives home to find Max Rubin waiting for him to sign a union contract. After berating Rubin for coming to his home, Lepke signs the paper. As Lepke escorts him from his home, three policemen burst in to frisk them for guns. After they leave empty-handed, Lepke demands to know what was so important about the contract that Max led police to his door. Max explains that Joe Rosen, a member of the Baker’s Union, was trying to block the union from paying Lepke a penny for every loaf of bread sold in Manhattan. Lepke orders Max to get Rosen kicked out of the union. Days later, Lepke and Gurrah go to collect their payoff from a furrier when they hear a gunshot. They see “Gino,” one of Luciano’s men, running away before an explosion demolishes the shop. Lepke declares Luciano is “muscling in” on his territory. That night, Mendy Weiss, disguised as a waiter, serves Gino a plate of spaghetti, which explodes in the thug’s face. Luciano is infuriated when he learns that Albert Anastasia sent Gino to extort businesses under Lepke’s protection. When Anastasia claims Lepke is getting too powerful, Luciano explains that as long as he is allowed to control the docks, he can smuggle in narcotics, which will make him a hundred times more powerful than Lepke. However, Lepke decides to enter the narcotics trade and sends Gurrah to Shanghai, China, to purchase heroin. Years later, Lepke has set up a thriving narcotics business. Kane, who has been reassigned to New York City to work with now district attorney Thomas Dewey, visits Lepke and warns him that the FBI knows he is selling drugs. Days later, Lepke is arrested for violating anti-trust laws. Once out on bail, Lepke learns that Joe Rosen, the baker he forced out of the union, is giving evidence to the grand jury. Lepke explodes and demands Rosen be killed in front of his men. Gurrah orders everyone out of the office, before pointing out to Lepke that everyone present is a potential witness to him ordering the hit. Early the next morning, disguised as a newspaper deliveryman, Mendy Weiss hands Rosen a bundle of papers hiding a bomb. As Mendy drives off, the bomb explodes. Later, Bernice and her father listen to famed journalist Walter Winchell on the radio, accusing Lepke of murdering Rosen. Her father demands Bernice leave Lepke, but she refuses, stating he has been a loving husband and father. Across town, Lepke’s men guard a shipment of drugs, when Luciano’s boys attack and kill them. This sets off a gang war and Gurrah talks Lepke into hiding in a movie theater. As Lepke and his men watch a gangster film, one of Luciano’s men breaks in, and shoots the projectionist. The gunshot is unheard due to gunfire on the movie soundtrack. The assassin then gets in position to fire on Lepke, but steps in front of the projector, blocking the light on the screen. Lepke shoots the man as more of Luciano’s men rush into the theater auditorium. A gunfight ensues, but Lepke escapes. Two years pass as Lepke moves from one furnished room to another, controlling his gang while on the run. One day, Lepke is summoned to a meeting with other crime bosses. Deciding to see Bernice and David before he goes, Lepke meets them at an empty amusement park. The reunion is cut short when armed men appear. As bullets fly, Lepke gets Bernice and David to safety, then finds Gurrah dying on a carousel. Gurrah’s asks “We made it to the top, didn’t we?” and dies. At the syndicate meeting, Luciano and Anastasia tell Lepke they have contacted Walter Winchell to negotiate with the FBI and that he must surrender. That night, Lepke is visited by Bernice. She refuses to spend the night with him, saying she does not want to say goodbye in a warehouse, so he tells her to leave. Although FBI director J. Edgar Hoover promised that Lepke would only serve twelve years in prison, he is sentenced to fourteen years in a Federal penitentiary. Only after serving that term, will Lepke be turned over to the State of New York. However, Federal prosecutors do not wait. Lepke is turned over to to stand trial in New York for murder with Thomas Dewey prosecuting. Hearing that Max Rubin is turning state evidence, Mendy Weiss follows Lepke’s orders and guns him down in front of his family as he buys a loaf of bread. Luciano hides the rest of Lepke’s gang so they can live to testify against him. Found guilty, Lepke is sentenced to death by electrocution. As he eats his last meal, he tells Robert Kane he should have let Dutch Schultz murder Dewey while he had the chance. After having his head shaved, Lepke is placed in the electric chair. He refuses to say any last words. A guard throws the switch and Lepke convulses before dying. Later, Kane emerges from the prison to find Bernice and David waiting and he escorts them escorts them home.