The story describes a young, middle-class Englishwoman who "had no luck". Although outwardly successful, she is haunted by a sense of failure; her husband is a ne'er-do-well, and her work as a commercial artist does not earn as much as she would like. The family's life exceeds its income, and unspoken anxiety about money permeates the household. Her children, a son Paul and his two sisters, sense this anxiety; they even claim they can hear the house whispering "There must be more money".
Paul tells his Uncle Oscar Cresswell about betting on horse races with Bassett, the gardener. He has been placing bets using his pocket money, and he has won and saved 320 pounds. Sometimes he says he is "sure" of a winner for an upcoming race, and the horses he names do in fact win, sometimes at remarkable odds. Uncle Oscar and Bassett both place large bets on the horses Paul names.
After more winnings, Paul and Oscar arrange to give the mother a gift of 5,000 pounds, but the gift only lets her spend more. Disappointed, Paul tries harder than ever to be "lucky". As the Derby approaches, Paul is determined to learn the winner. Concerned about his health, his mother rushes home from a party and discovers his secret. He has been spending hours riding his rocking horse, sometimes all night long, until he "gets there", into a clairvoyant state where he can be sure of the winner's name.
Paul remains ill through the day of the Derby. Informed by Cresswell, Bassett has placed Paul's bet on Malabar, at fourteen to one. When he is informed by Bassett that he now has 80,000 pounds, Paul, excited, tells his mother how "lucky" he is. Paul dies the next night.
