In New York City, in order to raise money for his campaign to become president of the local chapter of the longshoremen's union, crooked politico Jake MacIllaney extorts ten thousand dollars from miserly hypochondriac Charlie "Sleepout" Barnes. Although Jake gets his money, Sleepout turns him in, and Jake is arrested during a political rally. He initially disdains the lawyer assigned to him, young Dan Cabot, but Dan's scornful rejoinder impresses Jake, who then insists on hiring Dan. Later, Jake exacts his revenge by paying Sleepout's girl friend, Ginger, to drug him, after which they place his body in an iron lung and tell him he is near death. After he wakes, Sleepout decides to move to Arizona to recover. The night before the election, Jake stages a rally on the waterfront and directs his friend, Winnipeg Simmons, to hire pretty girls to distract rival O. K. Merritt and his henchmen. During the party, Merritt suddenly notices that all of his men have disappeared, but when he confronts Jake, Jake's men force him to drink until he becomes sick and must be hospitalized. Predictably, Jake wins the election, and the next day moves into his new office. There, he receives a letter from Dan refusing to represent him and offering to arrange a continuance on his trial against Sleepout. Jake knows that he must be tried before Sleepout returns to New York, and determines to convince Dan to change his mind. To this end, Jake visits Dan's apartment, and when he spies Dan's wife Linda singing, he hides behind the door and watches, captivated. When she spots him she states that she has ordered Dan not to represent a hoodlum, even though this has cost him his job. However, Dan returns soon after and cannot afford to turn down the $1,000 Jake offers. Jake then leases an office for Dan and instructs Winnipeg to decorate it sumptuously and act as his secretary. Winnipeg, discerning that Jake is in love with Linda and plans to break up her marriage, refuses to participate, but cannot resist when Jake promises to buy her a Ferrari. Next, Jake and his men draft a new contract for the longshoremen that charges exorbitant fees from the shipbuilders, despite the fact that current union president Pinelli will not approve it. Later, Sleepout's absence allows Dan to win Jake's extortion case, after which Jake provokes a fight between Dan and Linda. Dan escapes to his office, where Jake keeps him working all night and Winnipeg seduces him with alcohol and sympathy. Hours later, just as Dan kisses Winnipeg, Linda shows up and announces that she will seek a divorce. Meanwhile, Jake, who needs money to please his constituents, devises a racket in which he will steal $750,000 worth of watches, declare them drowned in the harbor, and then resell them on the black market. After convincing the insurance company that the watches are lost, Jake directs Dan to sell them, and then calls Linda to offer help. Upon hearing that she is going back to work as a standby singer at a television station, Jake secretly arranges for Linda to be allowed a rare onscreen appearance. He takes her to dinner after the show, and although she spurns his declaration of love, he vows to continue wooing her. Outside, a thug throws acid on them, which splashes Linda's arm, but the doctor proclaims her wounds superficial. Jake then tries to convince Linda that he must play dirty in order to gain power, and when she doubts his claim of wanting to help his fellow man, he explodes in anger, impressing her with his apparent underlying integrity. Over the next weeks, Jake rises in the estimation of the longshoremen, and soon the local representatives ask him to campaign against Pinelli. Against the advice of his cronies, Jake agrees. During the race, despite his strong showing in the polls, he remains convinced that he must invent a "hook" to swing the race in his favor. Pinelli grows nervous and bribes Jake's vice-president, Ed Barton, who then reveals Jake's watch scheme. While Jake is visiting Linda that evening, Dan arrives to insist that Linda take him back, but she refuses. Just then, on a tip from Pinelli, the police enter to arrest Jake, and to Linda's horror, Jake pins the blame on Dan. After they leave, Linda begs Jake to confess, offering herself in exchange for the favor. Jake reaches out for her, but when Linda recoils, he refuses the offer. He cannot bear her tears, however, and tries to persuade her that the longshoremen will embrace Dan as a hero for stealing to provide for them. Moved by Linda's devotion and his own speech, Jake realizes that heroic status is just the hook he has been looking for, and agrees to turn himself in. At the trial, Jake is sentenced to two years in jail but nonetheless, just as he has predicted, wins the union election. A reconciled Linda and Dan watch with amusement as Jake, still handcuffed to a policeman, is born away by the elated crowd.
