Paul's mother is obsessed with money and never seems to have enough. Money, or the lack thereof, is such a presence in the home that the house seems to whisper, "There must be more money!" Paul asks his mother why there is never enough money, and she tells him it is because his father is unlucky. Paul believes that luck brings money, so he begins riding his wooden rocking-horse frantically, waiting for a feeling to come to him that will let him know which horse will win the upcoming race. He begins betting without his mother's knowledge, and his Uncle Oscar learns of his betting and becomes his partner. He wins race after race and amasses $10,000. He anonymously sends his mother half of his winnings, believing this will make her happy and quiet the whispering house. But things only worsen. The house whispers louder and more frantically than ever.

Suddenly, he is without his lucky vision. Two big races go by without him knowing who will win, and he is frantic with worry. Even his coldhearted mother begins to worry about him. The night before the derby, she finds him desperately riding his wooden rocking-horse, and he suddenly exclaims "Malabar" and falls, unconscious, to the floor. Malabar does win the derby, and the boy wakes long enough to realize that he has amassed $80,000. But the boy never gets to enjoy any of his winnings, because he dies that night. The mother realizes the folly of her avarice when she hears her brother say, "But, poor devil, poor devil, he's best gone out of a life where he rides a rocking-horse to find a winner." Her brother's voice condemns her for the pressure she has put on her young son because of her greed.

Paul becomes obsessed with horseracing through a desire to please his mother. As a shy and sensitive boy, Paul will stop at nothing to please his mother and gain her love. For him, horseracing is not about winning money—it is about winning his mother's love.

His mother, Hester, believes that the key to happiness is luck, because luck brings you money. As a result of Hester's desperate desire for luck, Paul becomes determined to successfully bet on the horses, thereby finding luck and using it to ring money into the household for his mother.

Unfortunately for Paul, when Hester starts getting this money, all she wants is more and more. It is by riding his rocking horse that Paul ascertains the name of the winning horses, but rather than rocking his way to a peaceful home and his mother's love, Paul ultimately rocks himself to death.

In The Rocking Horse Winner, Paul becomes obsessed with horse racing to please his mother, who craves money. Since he wants to earn her love, as well as reduce the atmosphere of anxiety he feels all the time in the house, Paul tries to win as many horse racing bets as he can. He works with his Uncle Oscar and Bassett, the gardener, to predict the winners of enough races that they can give his mother 5,000 pounds.

Sadly, even after his mother gets this money, it's not enough. It only whets her appetite for more and more. The atmosphere in the house becomes more pressured, so that even the walls seem to be saying, over and over, "there must be more money!" By this point, Paul has internalized his mother's obsession. He wants at all costs to please her. He learns if he ride his rocking horse often enough and fast enough, he can figure out which horse will win the next race. He rides and rides the rocking horse to find out the winner of the derby, so his mother can become rich. But doing so kills him.

The story is parable about the limitless quality of greed and the effect it can have on children who lack any adult mechanism for putting boundaries between themselves and a parent's need.