Lilly Dillon (Angelica Huston) is a veteran con artist. She works for a bookmaker, Bobo Justus (Pat Hingle), making large cash bets at race tracks to lower the odds of longshots. On her way to La Jolla for the horse races, she stops in Los Angeles to visit her son Roy (John Cusack), a small-time grifter whom she has not seen in eight years. She finds him in pain and bleeding internally after one of his victims caught him pulling a petty scam and punched him in the stomach. When medical assistance finally comes, Lilly confronts the doctor, threatening to have him killed if her son dies.
At the hospital, Lilly meets and takes an instant dislike to Roy's girlfriend, Myra Langtry (Annette Bening), who is a few years older than her son. Lilly urges her son to quit the grift, saying he literally does not have the stomach for it. Because she leaves late for La Jolla, she misses a race where the winner was paying 70 1. For this mistake, Bobo burns her hand with a cigar.
Myra, like Roy and Lilly, plays all the angles. When her landlord demands payment of late rent, she uses her sex appeal to lure him into bed and forget the rent. She makes a similar offer to a jeweler (Stephen Tobolowsky) to get what she wants for a gem she is trying to pawn.
Upon leaving the hospital, Roy takes Myra to La Jolla for the weekend. On the train, she notices him conning a group of sailors in a rigged dice game. Myra reveals to Roy that she is also a grifter and is looking for a new partner for a long-con operation.
Myra describes her long association with another man, Cole (J. T. Walsh), and how they took advantage of wealthy marks in business cons, including a greedy oil investor, Gloucester Hebbing (Charles Napier). A flashback scene in a plush office building culminates in a fake FBI raid with a fake shooting of Myra to discourage Hebbing from going to the police.
Roy, who insists on working only short-term cons, resists the proposition, fearing she may try to dupe him herself. Myra, seeing Lilly's power over Roy, accuses him of having an incestuous interest in Lilly. Infuriated, Roy strikes her. Myra then plans her revenge. She lets it be known that Lilly has been stealing from Bobo over the years and stashing money in the trunk of her car. Lilly is warned by a friend and flees. Myra follows with the intention of killing her.
Roy is called by an FBI agent to identify his mother's body, found in a motel room with the face disfigured by a gunshot wound. While identifying it as Lilly's, he silently notes that there is no cigar burn on the corpse's hand. Coming back home, he finds Lilly trying to steal all of his money. Lilly reveals that she shot Myra in self-defense at the motel and arranged the scene to appear as though Myra's body was actually Lilly's. Roy refuses to let Lilly depart with his money. Lilly pleads with him, then attempts to seduce him, even going so far as to tempt Roy by claiming he is not really her son. Roy rejects her, disgusted. Angered, Lilly swings a suitcase at him and unintentionally breaks a glass he was drinking from into his neck, slashing an artery.
Lilly sobs convulsively while she packs up the money as her son bleeds to death on the floor. In the penultimate shot, she is seen dressed in red, riding an elevator that is heading down. Then she gets into Roy's car and drives off into the night.
Output: Why does Lilly claim Roy literally does not have the stomach for the grift?