After years of toiling in the oil fields of Galveston, Texas, Frank Duncan, a shrewd, ambitious oil driller, conceives of a plan to steal millions of dollars of crude oil. To finance his scheme, Duncan contacts Houston mob boss Paul "Paulie" Atlas through Zoe Crane, the lounge singer girl friend of Atlas’ second-in-command, Gordie Shay. Impatient for wealth and stature, Zoe, who changed her name from Carrie Hemper after deserting her husband, an old oil drilling friend of Duncan’s, puts Duncan in contact with Atlas. After Duncan outlines his plan to bribe the foremen into allowing him to tie into their lines and thus steal fuel from the tanks, Atlas agrees to back Duncan. Duncan proposes forming a dummy corporation as a front in case something goes wrong and suggests appointing his good-natured yet dim-witted friend Louie Phelan to be its head. Once Duncan departs, Atlas reassures Shay that he plans to dump Duncan as soon as he is no longer useful. When Shay and Atlas travel to St. Louis to present the plan to Emile Constant, the head of a nationwide crime syndicate, Constant warns Atlas that the operation must be nonviolent. Soon after, Duncan is visiting his sweetheart Madge at the Derrick Café where she waits tables, when Zoe comes to deliver a message from Atlas, arranging for a meeting later that night. After consummating his deal with Atlas, Duncan appoints Louie head of the company, and the naïve Louie blithely signs all contracts presented to him. When Shay comes to visit Duncan in his office one day, the wary Duncan surreptitiously tapes their conversation. After laying out a plan to siphon oil from the refineries at the docks, Duncan instructs Shay to hijack a load of pipes from a truck that evening, and cautions that there must be no violence. Deciding to sabotage Duncan’s advancement by insuring that the hijacking fails, Shay tells his thugs to kill one of the drivers. With the murder of the truck driver, federal agents are called in to investigate. When Constant confronts Duncan about the killing, Duncan plays the tape recording in which he tells Shay to avoid violence. Furious, Constant fires Shay and after installing Duncan in his place, warns Atlas that he will hold him responsible for Shay’s subsequent indiscretions. That night, Chris Barker, one of Shay’s lieutenants, forces Zoe at gunpoint to phone Duncan and beg him to lend her $25,000, arranging to meet him later that evening at the observatory atop the Houston Justice Building. Upon arriving at the observatory, Duncan finds Barker waiting for him, gun in hand, demanding the money. After Duncan hands over the envelope, Barker announces his plan to kill him anyway, prompting Duncan to shove him over the side of the building. Duncan then hurries to Zoe’s apartment, where he finds her severely beaten by Shay, who is still there. As Duncan lashes out at Shay, Atlas arrives and begs Duncan to spare his protégé. Duncan then consents to give Shay a chance at redemption by coercing the uncooperative owner of a refinery into selling his property. When Barker’s body is found, federal agents identity him as a member of Constant’s syndicate and focus their investigation on Houston. Duncan, meanwhile, double-crosses Shay by alerting the authorities about the sabotage attempt at the refinery. After lobbing a grenade into one of the derricks, Shay is arrested by the police and exposes Atlas’ role in the oil hijacking scheme. While trying to flee the authorities, Atlas is shot down in the street. Upon learning of the situation, Constant sends his two thugs, Don Stokes and Kalo, to eliminate Duncan. After arriving in Houston, Constant’s enforcers go to Duncan’s offices, where, through the intercom, Duncan overhears them pummeling Louis in the anteroom. Fleeing out the back, Duncan phones Zoe, instructs her to pack her things and meet him at the Derrick Café. Still believing in Duncan’s rectitude, a dazed Louis notifies the police about his friend’s peril. At the Derrick Café, Duncan tricks the sweet, unsuspecting Madge into driving to his apartment and retrieving his clothes and money from the safe. When Madge arrives, she finds Zoe cleaning out the safe, and Zoe then coldly informs Madge that Duncan has double-crossed her. Stuffing her purse with cash, Zoe hurries out of the building but is picked up by Stokes and Kato. After forcing her to divulge Duncan’s location, Stokes and Kato shoot her and throw her body out of the moving car. As Duncan waits at the café, Madge, shaken, notifies the police. Stokes and Kato arrive at the café first, however, and shoot it out with Duncan as police sirens wail in the distance. After disposing of his assailants, the wounded Duncan hears Louis, pleading over the police megaphone, to give himself up. With no other alternative, Duncan surrenders.