"Fast Eddie" Felson is accompanied by his partner, Charlie, at a pool room in a small town. Pretending to be salesmen on their way to a convention, Eddie and Charlie convince onlookers that Eddie is a drunk blowhard, and induce them to bet on Eddie to lose a trick shot. He wins and takes their money. Eddie and Charlie arrive in New York City, where Eddie challenges the legendary player Minnesota Fats to play straight pool for $200 a game at Ames Billiards in Manhattan. After initially falling behind, Eddie surges back to being $1,000 ahead and suggests raising the bet to $1,000 a game. Eddie gets ahead $11,000 and Charlie tries to convince him to quit, but Eddie insists the game will end only when Fats says it is over. Fats agrees to continue after a spectator, the professional gambler Bert Gordon, labels Eddie a "loser". After 25 hours and an entire bottle of bourbon, Eddie is ahead over $18,000, but loses it all along with all but $200 of his original stake. Fats declares the game over. At their hotel later, Eddie leaves a sleeping Charlie without saying goodbye. Eddie stashes his belongings in a locker at a bus terminal, where he meets Sarah Packard, an alcoholic. They begin a relationship and he moves in with her. Charlie finds Eddie at Sarah's apartment and tries to persuade him to go back out on the road. Eddie refuses and Charlie realizes he plans to challenge Fats again. Eddie learns that Charlie had money he could have used to rebound and beat Fats. Eddie dismisses Charlie as a scared old man and tells him to "lay down and die by yourself". Eddie joins a poker game where Bert is playing. Afterward, Bert tells Eddie that he has talent as a pool player but no character. He figures that Eddie will need at least $3,000 to challenge Fats again. Bert calls him a "born loser" but nevertheless offers to stake him in return for 75% of his winnings; Eddie refuses. Eddie goes back to hustling to get the money he needs to play Fats. After hustling a local player at a pool room near the waterfront, Eddie is attacked after winning and his thumbs are broken. After Sarah helps Eddie convalesce, and when he's ready to play, he agrees to Bert's terms, deciding that a "25% slice of something big is better than a 100% slice of nothing". Bert, Eddie and Sarah travel to the Kentucky Derby, where Bert arranges a match for Eddie against a wealthy local socialite named Findley. The game turns out to be three-cushion billiards, not pool. When Eddie loses badly, Bert refuses to keep staking him. Sarah pleads with Eddie to leave with her, saying that the world he is living in and its inhabitants are "perverted, twisted, and crippled"; he refuses. Seeing Eddie's anger, Bert agrees to let the match continue at $1,000 a game. Eddie comes back to win $12,000. He collects his $3,000 share and decides to walk back to the hotel where he discovers that Sarah has committed suicide, because of Bert's sadism. Eddie returns to challenge Fats again, putting up his entire $3,000 stake on a single game. He wins game after game, beating Fats so badly that Fats is forced to quit. Bert demands half of Eddie's winnings and threatens to have him beaten unless he pays. Eddie says he will come back to kill Bert if he survives, shaming Bert into giving up his claim by invoking Sarah's memory. Instead, Bert orders Eddie never to walk into a big-time pool hall again. Eddie and Fats compliment each other as players, and Eddie walks out.

Luis "Mountain" Rivera is an aging heavyweight boxer. He is managed by Maish Rennick, and Army serves as his cutman. During his latest bout, against young up-and-comer Cassius Clay, Mountain takes a serious beating and the doctor refuses to certify Mountain for future fights. Afterward, Maish is confronted by Ma Greeny and her thugs. They threaten Maish's life if he fails to repay them for the losses they incurred after betting that Mountain would go down in the fourth round of the match - a fix that Maish had guaranteed. Maish's deal with them had been that they should deduct from their winnings the vast sums of money that Maish's betting losses had run up with them. Meanwhile, Mountain struggles to find a job and visits an employment agency, where he meets Grace Miller. Grace is initially standoffish but quickly becomes sympathetic to Mountain, and says she'll be in touch. Later, Grace meets with Mountain to tell him of an opening for a counselor position at a children's camp, which interests Mountain. The two bond over a drink and Mountain shares stories of his time in the ring. Mountain returns to his apartment - shared with Maish and Army - where Maish proposes the three get into professional wrestling. Mountain is reluctant, not liking the staged nature of wrestling. Maish, hoping that Mountain will forget about the job interview, takes him to a bar, where they both get drunk. Army arrives at the bar to remind Mountain about the appointment. However, Rivera embarrasses himself at the hotel where the interview is to take place by behaving drunkenly in plain sight of the camp owners. After this episode, Grace confronts Maish in tears, condemning him for controlling Mountain and ruining his chance to make a new life for himself. Maish responds forcefully and eloquently to Grace's accusation that he has been over-controlling of Mountain, disputing the notion that he cares nothing for the boxer, his best interests, and his future. He tells Grace that she must stop daydreaming and recognize that her idealized conception of Luis Rivera is as false and damaging to the fighter as is Maish's alleged mediocre management of the boxer's career. Further, he tells her that her so-called "vision" for Rivera's post-boxing future as a counselor at a children's summer camp is as naïve and pathetic as it is improbable. To pay off Maish's gambling debts, Mountain agrees to perform as Native American wrestling persona "Big Chief Mountain Rivera." Just prior to entering the ring for his first match, an overwhelming tide of humiliation sweeps over Mountain, causing him to change his mind. Maish blurts out that he bet against Mountain in the fight against Clay, and as Rivera attempts to leave the locker room, Ma Greeny and her thugs enter, threatening Maish. This causes Mountain to change his mind and agree to wrestle, thereby allowing Ma to be paid and saving Maish's life. In the final scene of the film, Mountain enters the ring amidst jeering ridicule to face Haystacks Calhoun, a wrestler from Arkansas billed at 601 pounds (273 kg).