Curious to see if people on the other side of the globe walk upside down, Robert, Anthea, Cyril, Jane, and their baby brother start digging a hole to Australia. They don't get too far, however, before they dig up a furry brown creature with bat's ears. It is a Psammead, an ancient Sand-fairy. The Sammyadd, as the children call it, grumpily tells them that he is obliged to grant their wishes, because making people's wishes come true is what Sand-fairies do. However, there is one catch: the wishes come undone at sunset. No matter how carefully the children plan, their wishes keep backfiring, and they realize that you have to be careful what you wish for—you may get it.