The Psammead is an 'it', an ancient, ill-tempered sand-fairy with a spider-shaped body, bat-like ears, and snail-like eyes. It is grumpy but has the power to grant one wish a day, which must be made before sunset. Five siblings—Cyril, Anthea, Robert, Jane, and infant Hilary—encounter It and experience the highs and lows of frivolous wish-making.