Jay Trotter, a cab driver with a penchant for gambling, stumbles upon an extraordinary tip about a horse race while eavesdropping on his passengers. Although Jay promises his wife Pam that he'll quit betting, he can't resist the allure of one last gamble. Using the windfall information, he places a bet and watches as the horse wins, setting off a miraculous streak of luck. As his winnings accumulate, Jay's exuberance grows, leading him to continue betting and convincing himself that he might have found a surefire path to fortune.

Throughout his roller-coaster day at the racetrack, Jay encounters a colorful array of characters, from rival gamblers to eccentric regulars, all with their own quirks and insights on lady luck. As he hops from one high-stakes race to another, the tension mounts with each bet, alongside mounting pressure from his long-suffering wife and skeptical friends. With fortunes constantly shifting, Jay rides a wave of highs and lows that test not only his luck but also his relationships and sense of self, inching closer to a poignant realization about the nature of his obsession.