The setting for this book is the First World War. It features the same children who were in the original story of Five children and It by E. Nesbit, only now they are nine years older, and the oldest two brothers are fighting in the war in France. While digging in their garden in Kent, the two youngest children happen to find the Psammead, or Sand Fairy, who is a magical creature that grants wishes. They met him nine years earlier when they were staying in their uncle's castle.

They soon realize that he has lost his powers and they set out to find out about his past life, uncovering the fact that it was rather violent. The setting during the war helps the Sand Fairy to repent for having invaded a country and all his other past awful deeds. He needs to repent in order to get his powers back and to be able to return to where he came from. I felt rather disillusioned about him, as in the previous book he had seemed a positive influence. This book shows him to be very much the opposite, which saddened me. I also felt a bit of anger towards the writer for breaking this illusion for me.

There is correspondence between the children at home and the brothers at war, which provides a bit of background to the war. The tragedies of the war are revealed through one of the brothers being wounded and the other dying. The book brought to life the feelings that are experienced when a sibling dies, and made me wish it would never happen to me. It was an interesting book, but it also shattered some of the happy ideas I had of the Sand Fairy from before.

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