Like Nesbit's Railway Children, the story begins when a group of children move from London to the countryside of Kent. While playing in a gravel pit soon after the move, they uncover a rather grumpy, ugly and occasionally malevolent sand-fairy known as the Psammead who is compelled to grant one wish of theirs per day.

The children's wishes are:

Chapter I: To be as beautiful as the day. Because the servants then do not recognize them and shut them out of the house, subsequent wishes are all with the proviso that the house servants should not be able to perceive the results of the wish.

Chapter II: To be rich beyond the dreams of avarice (refined to: That the gravel pit be full of gold pieces, specifically spade guineas).

Chapter III: That everyone would love the Lamb (the baby brother). This wish produces the result that various people attempt to kidnap the child.

Chapter IV: That the four older children would grow wings, and be able to fly.

Chapter VI: That their house would become a castle under siege by knights (This wish was the result of Robert- the only one allowed out that day- wishing...
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