A young, reformed gambler must return to playing high stakes poker to help a friend pay off loan sharks, while balancing his relationship with his girlfriend and his commitments to law school.
John Dahl directed this exploration of New York private clubs devoted to high-stakes poker, with first-person narration from the film's central figure, law student Mike McDermott (Matt Damon), who loses his entire savings to Russian club owner Teddy KGB (John Malkovich). Mike then turns away from cards, devoting his attentions to his law studies and his live-in girlfriend Jo (Gretchen Mol), who's concerned when Mike's former gambling buddy Worm (Edward Norton) is released from prison. She has good reason to worry, since it takes Worm only a matter of minutes to draw Mike back into poker action. When she learns Mike has returned to the poker clubs, she moves out, and Mike begins to lose interest in his studies. Worm has a prison debt, and the threatening Grama (Michael Rispoli) wants the money. Mike not only indulges the irresponsible Worm, he gets involved in Worm's debts. When Grama demands $15,000 on a five-day deadline, the two buddies go into high gear with a non-stop, no-sleep gambling binge that spirals downward toward an ultimate confrontation with Teddy KGB.
Gifted poker player Mike McDermott (Matt Damon) loses his entire $30,000 bankroll in a hand of Texas hold'em against Teddy "KGB" (John Malkovich), a Russian mobster who runs an illegal underground poker room. Shaken, Mike decides to concentrate on law school, while promising his girlfriend and fellow law student Jo (Gretchen Mol) not to play the game anymore. Mentor and fellow rounder Knish (John Turturro) offers him a part-time job driving a delivery truck to make ends meet.
Time passes, and Mike is true to his promise. He focuses on school and work until his childhood friend Lester "Worm" Murphy (Edward Norton) is released from prison. Worm is also a card player, who owes an outstanding debt accumulated before his incarceration. At Worm's influence, Mike is soon rounding again, which interferes with his studies and hurts his relationship with Jo.
When Worm is given a five-day deadline to pay off his debt, Mike joins him in a furious race to earn the money. Worm wants to cheat to win, but Mike insists on playing straight. Played out through several card games in and around New York City, the two nearly make the $15,000 needed, but the pair are caught cheating and lose their entire bankroll. After this, Worm decides to leave the city, and he advises Mike to do the same. This is when he reveals to Mike that his debt is owed to KGB, the same Russian mobster who cleaned Mike out of his $30,000 bankroll several months before. Infuriated, Mike cuts ties with Worm once and for all.
Mike refuses to flee. In a race against time to pay off Worm's debt, Mike gets his shot at redemption by placing his life on the line against the man who forced him out of the game. With the help of a $10,000 loan from his law school professor Petrovsky (Martin Landau), Mike sits down to play KGB in a no limit, heads-up game of Texas Hold'em.
In two heated heads-up matches, Mike beats KGB, winning enough to pay off Worm's debt, repay his loan to the professor, and regain his original bankroll of about $30,000. The movie ends with Mike officially dropping out of law school, saying goodbye to Jo, and going to Las Vegas to play in the World Series of Poker Main Event.
