When Tommy Riley’s mother dies from cancer, his father, John, loses the family fortune on drinking and gambling, and they are forced to leave their wealthy suburban community of Bridgeport and move to Chicago, Illinois. At his new, inner-city high school, Tommy is harassed by gang members, and angers a classmate named “Spits” when he refuses to give up his seat. After school, Spits and his gang, the Storm Troopers, led by “Shortcut,” surround Tommy in the schoolyard. However, a rival gang member, Abraham “Lincoln” Haines, interrupts, and Shortcut pulls a knife. School guards break up the fight before it escalates. Later, Tommy is approached by two debt collectors who claim his father owes $1,250 to their boss, “Sharky.” At Millie’s diner, Tommy tells his classmate, Dawn, who works as a waitress, that he can only afford coffee, so she asks her mother, Millie, to hire Tommy as a dishwasher. As he begins work, Shortcut and two Storm Troopers follow him outside on a break and attack, but Tommy defends himself. The young men are interrupted by underground boxing promoter “Pappy Jack,” who warns Shortcut not to get hurt before his next fight. Inside the diner, Pappy Jack compliments Tommy on his fighting, and Tommy explains that he won a “Golden Gloves” amateur boxing championship back in Bridgeport. Pappy Jack tells him about Jimmy Horn’s weekly amateur bouts, and offers him $750 to fight a few rounds the following night. Tommy negotiates for $1,250, so he can repay his father’s debt. Later, Tommy’s father, John, tells him he got a job selling medical supplies, and will soon move them out of the “slums.” However, John must leave home for a month to attend a company training program, and Tommy assures him he can look after himself. When Tommy mentions the debt collectors, John reveals that he gambled to pay off his wife’s hospital bills. After apologizing to his son, John telephones “Sharky,” promising to repay his debt soon, and demands that he leave Tommy alone. The next night, Tommy arrives at the arena for the fight and meets his cornerman, Noah. When Pappy Jack gives him illegally lightweight gloves, Tommy realizes it is an unorthodox fight. He befriends classmate and fellow fighter, Romano Essadro, who gives him advice about his opponent, “Black Death.” As owner Jimmy Horn looks on, Tommy at first takes a beating, but revives and, with Noah cheering him on, knocks out both Black Death and the referee. Afterward, Tommy asks for his money, but Pappy Jack tells him to see Horn a few days later. Word spreads at school about Tommy’s win, but he denies it to Lincoln Haines. He later sees Lincoln training at the Windy City Boxing Club when he goes to collect his money from Jimmy Horn. Horn, who is a retired champion boxer, pays Tommy and asks him to be one of his regular fighters, but Tommy fears he will suffer brain damage. Horn feigns understanding, and bids Tommy farewell, but orders Pappy Jack to make sure the boy is recruited. Later, Romano encourages Tommy to accept the offer. When Tommy pays back his father’s debt, Pappy Jack witnesses the transaction and telephones Sharky. Later, Dawn waits on Tommy’s doorstep for him to return, and asks him about his fight. Tommy insists he will not be fighting anymore, but Pappy Jack arrives, orders him into his automobile, and takes him to see Horn. Horn claims that Tommy’s father was in debt to Sharky for $15,000, but he paid off the gangster, so now Tommy must repay the favor by becoming one of his fighters. Later, Tommy witnesses the Storm Troopers beating Lincoln, and comes to his defense. As they hide together in an abandoned building, Lincoln wonders aloud why Tommy rescued him. Lincoln reveals that he has an infant daughter, and illegal boxing matches are his only chance of getting them out of the ghetto. At the arena, Lincoln’s heavyweight opponent kicks him in the head, and the referee does not stop the fight. Tommy is outraged, but Lincoln throws a knockout punch, and wins the bout. Dawn asks Tommy why he has not been showing up at school or the diner, and gives him a college application from his teacher, Miss Higgins. Tommy tells Dawn about Horn’s blackmail, and that he is required to compete in four more bouts. He worries that Horn will kill his father if he refuses. Tommy beats several opponents at the arena, but his friend, Romano, is blinded when his opponent, Shortcut, puts a chemical on his glove and rubs it in Romano’s eye. Despite Tommy’s attempt to stop the fight, Romano is knocked unconscious. At school, Miss Higgins tries to encourage Tommy to go to college. He searches hospitals for Romano, and finds him several days later at a county hospital for the poor. Romano is hooked up to a breathing machine, and his face is disfigured. Tommy learns that his friend is brain-dead. At his next fight with Shortcut, Tommy knocks him out in the first round, but ignores Horn’s instructions to land a fatal blow. Afterward, he returns home and makes love to Dawn. At the gym, Lincoln collapses during training, and Noah believes he may have suffered brain damage after being kicked in the head during his last fight. The doctor agrees and “benches” Lincoln for sixty days. When Tommy arrives for his final fight, however, he is surprised to learn that Pappy Jack has switched his opponent at the last minute, and he will face Lincoln in the ring. Lincoln reveals that Horn promised to make him a professional fighter if he competes, and is offering a $20,000 reward. When Tommy refuses to fight, Lincoln begs him to participate, insisting it is his only chance to get ahead. Tommy tells Horn about Lincoln’s poor health, but Horn warns him against dropping out. Pappy Jack tells Tommy he could be the welterweight champion and earn over $2 million. Dawn arrives to watch, and Horn insists she sit next to him, which angers Tommy. During the fight, he avoids hitting Lincoln in the head, and tells him that Horn wants one of them to die in the ring, which will earn him a big payoff. Tommy orders Lincoln to knock him out, but Lincoln refuses. Furious, Jimmy Horn jumps into the ring to force Lincoln to fight. When the boy quits, Horn punches Lincoln, knocking him out of the ring. Tommy challenges Horn to fight: If Tommy wins, he will regain freedom, and if he loses, he will belong to Horn. Horn challenges him to a bare-knuckle fight, and taunts Tommy, dodging his punches. Tommy suffers a severe beating before Horn throws him over the ropes. Returning to the ring, Tommy pretends to have a broken hand, then surprises Horn with a knockout punch. As Horn collapses, Tommy wins his freedom.