A ruthless war takes place between the Palmero and Ricca gangs after the two leaders end a partnership. When two innocent children are killed in the conflict, the public outrcy forces the gang leaders to flee the city. The socially ambitious Mike Palmero goes to Florida, where he attempts to finesse his way into high society after becoming wealthy through bootlegging. He still surrounds himself with bodyguards and continues to run his gang, while Tony Ricca runs his operation from the outskirts of Chicago. Mike's beautiful daughter Maria, who has been reared in a French convent, loathes her father's underworld activities, even though she knows the money he earns from them will raise her to social prominence. Mike hires a publicity woman and invites the well-known people of the city to a party in order to get Maria's picture in the newspapers. At the party, Maria meets handsome architect Marco Smith, who is actually Tony's son. Marco has disowned his father, however, and assumed the name of Smith to distance himself from Tony's lifestyle. Maria and Marco fall in love, but Maria is afraid to tell her father for fear of feuling the Palmero-Ricca feud. As members of the gangs continue to kill one another, Mike orders the murder of Benedicto, Tony's favorite son. Tony retaliates by having Maria's brother Joe killed in a hail of machine gun fire. While dying, Joe informs his father that Marco is also a Ricca. Meanwhile, Marco and Maria have eloped, and they return to tell her father. Mike plans to kill Marco but delays the murder in order to torture him with anxiety. Maria's grandmother Nina helps Marco escape, however, and kills her son rather than allow him to order the execution of Marco and Maria. The young lovers are thus free to build a new life together, while the rival gangs dwindle under the attrition of constant reprisals.