Five children staying in their eccentric uncle's labyrinthine mansion for protection during World War I befriend a sand fairy who has the power to grant wishes.

"It" is a Psammead, an ancient, ugly, and irritable sand fairy the children find one day on a secret beach at their uncle's mansion. It grants them one wish per day, lasting until sunset. But they soon learn it is very hard to think of really sensible wishes, and each one gets them into unexpected difficulties. Magic, the children find, can be as awkward as it is enticing.—craig47