Stanley Yelnats has been sent to Camp Green Lake for the theft of a pair of shoes, a crime for which he is completely innocent. Most people would regard such a blatant injustice as a piece of really bad luck. But to Stanley, it's much more than that; it's the product of a curse that has been hovering over his family for generations.
Once upon a time, Stanley's great-great-grandfather Elya received a pig from a gypsy by the name of Madame Zeroni. In return, he promised her that he would carry the one-legged gypsy up a mountain and sing a song she'd taught him.
In the event, Elya became disillusioned with Madame Zeroni and didn't make good on his promise. Instead, he boarded a boat bound for the United States. Although the two were far apart, Elya often thought about the woman he left behind. He also believed, as his great-great-grandson Stanley still does, that Madame Zeroni had put a curse on him for not living up to the promise he made to her.
Elya may be long dead, but Stanley's convinced that everything bad that happens to him, including being wrongly convicted and sent to Camp Green Lake, is all down to the Yelnats family curse.