Aunt Polly punishes Tom by forcing him to whitewash a fence on a Saturday morning when he had planned to have fun. He is feeling hopeless and despondent. He thinks sorrowfully of all the pleasures he had lined up for the day. He thinks of the other boys, who don't have chores to do, coming by and making fun of him for having to work. He wonders if there is a way he can trade them something so that they will do the painting for him while he goes off to play. However, he soon realizes he has nowhere near enough to entice anyone. Then we learn:

At this dark and hopeless moment an inspiration burst upon him! Nothing less than a great, magnificent inspiration.

Tom decides to use reverse psychology and make whitewashing a fence seem so desirable that the other boys will envy him and want to do it. As Tom says to Ben of the whitewashing:

Well, I don’t see why I oughtn’t to like it. Does a boy get a chance to whitewash a fence every day?

Tom's reluctance to share the "fun" of whitewashing soon has the other boys clamoring to do so and even paying for the favor.