When four brothers and sisters discover a Psammead, or sand-fairy, in the gravel pit near the country house where they are staying, they have no way of knowing all the adventures its wish-granting will bring them.

Artemis's mother has contracted a deadly disease -- and the only cure lies in the brain fluid of African lemurs. Unfortunately, Artemis himself was responsible for making the lemurs extinct five years ago. Now he must enlist the aid of his fairy friends to travel back in time and save them. Not only that, but he must face his deadliest foe yet...his younger self.